WO2014174754A1 - Communication system, transmission device, reception device, communication method, and program - Google Patents

Communication system, transmission device, reception device, communication method, and program Download PDF

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Publication number
WO2014174754A1
WO2014174754A1 PCT/JP2014/001472 JP2014001472W WO2014174754A1 WO 2014174754 A1 WO2014174754 A1 WO 2014174754A1 JP 2014001472 W JP2014001472 W JP 2014001472W WO 2014174754 A1 WO2014174754 A1 WO 2014174754A1
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Prior art keywords
transmission
unit
prefix
symbol
communication system
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PCT/JP2014/001472
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French (fr)
Japanese (ja)
Inventor
慎哉 杉浦
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国立大学法人東京農工大学
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Priority to JP2015513505A priority Critical patent/JP6206885B2/en
Publication of WO2014174754A1 publication Critical patent/WO2014174754A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
    • H04L27/2607—Cyclic extensions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference

Definitions

  • the present invention relates to a communication system, a transmission device, a reception device, a communication method, and a program.
  • a transmission interval of each symbol that does not cause intersymbol interference is given by a Nyquist rate determined by an available frequency band W (for example, see Patent Document 1).
  • a Nyquist rate determined by an available frequency band W
  • FTN Faster-Than-Nyquist
  • Non-Patent Documents 3 and 4 FTN demodulation algorithms (time-space equalization algorithms) have been devised in accordance with the recent improvement in signal processing capability (for example, see Non-Patent Documents 3 and 4).
  • the Viterbi algorithm is applied by regarding received data in which intersymbol interference has occurred as a convolutional code.
  • Non-Patent Document 4 a repetitive signal based on SIC (successive interference cancellation) is used.
  • a precoding algorithm see, for example, Patent Document 1 that compensates for inter-symbol interference on the transmission side and a timing synchronization algorithm (for example, see Patent Document 2) suitable for an FTN transceiver have been developed.
  • Non-Patent Document 5 a technique for reducing intersymbol interference caused by the influence of frequency selective fading in a channel through which a signal is transmitted is known (for example, see Non-Patent Document 5).
  • Non-Patent Document 3 A. D. Liveris and C. N.
  • Non-Patent Document 4 F. Rusek and J. Anderson, “Multistream faster than Nyquist signaling,” IEEE Transactions on Communications, vol. 57, no. 5, pp. 1329-1340, May 2009.
  • Non-Patent Document 5 Hayashi Kazunori “Fundamentals of Modulation / Demodulation and Equalization Technologies” Proc. MWE2004, pp523-532, 2004.
  • Non-Patent Document 6 Nan Wu and Lajos Hanzo, "Near-Capacity Irregular-Convolutional-Coding-Aided Irregular Precoded Linear Dispersion Codes" IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 6, JULY 2009.
  • Patent Document 1 European Patent No. 2342832
  • Patent Document 2 European Patent No. 2436140 Specification
  • a band-limited communication system including a transmission device and a reception device, wherein the transmission device is predetermined at the head of each block of transmission data and at the end of each block.
  • a prefix adding unit that adds a prefix obtained by copying the length of data, and a transmission unit that transmits each symbol of the transmission data to which the prefix is added at a time interval shorter than the Nyquist rate according to the communication system band.
  • a prefix removing unit that removes a prefix from each block of received data, and a symbol generated by transmitting a symbol at a time interval shorter than the Nyquist rate in each block from which the prefix is removed.
  • a communication system comprising an interference canceling unit that cancels inter-interference, and To provide a communication method according to the communication system.
  • the interference removal unit may ignore intersymbol interference that occurs in a section longer than the prefix length in each block of received data, and remove intersymbol interference that occurs in a section that is shorter than the prefix length.
  • the interference removal unit may remove intersymbol interference from the received data based on the time interval of each symbol in the transmission unit.
  • the transmission device further includes a transmission filter that restricts the bandwidth of the transmission data to which the prefix is added to a predetermined bandwidth and inputs the transmission data to the transmission unit, and the interference removal unit is based on the filter characteristics of the transmission filter. Intersymbol interference may be removed from the received data.
  • the transmission device may transmit information indicating the time interval in the transmission unit to the reception device.
  • the transmission device may transmit information indicating the filter characteristics of the transmission filter to the reception device.
  • the prefix adding unit may determine the prefix length based on the time interval in the transmitting unit.
  • the prefix adding unit may determine the length of the prefix based on the filter characteristics of the transmission filter.
  • the prefix adding unit may determine the length of the prefix based on the length of each block of transmission data.
  • the interference removing unit may convert the received data into a frequency domain signal and remove an intersymbol interference component in the frequency domain.
  • the interference removal unit approximates an equivalent channel matrix indicating intersymbol interference in a block by a cyclic matrix, and multiplies each frequency component of received data by a weight coefficient corresponding to the cyclic matrix to remove intersymbol interference. Good.
  • the interference removal unit may correct the magnitude of random noise superimposed on the received data based on the time interval in the transmission unit to remove intersymbol interference.
  • the transmitting device receives a source bit string indicating information to be transmitted, divides the source bit string into a plurality of sub-blocks having a predetermined length, and converts the source bit string of each sub-block into a partial bit value of the source bit string.
  • the block further includes a modulation unit that converts a symbol symbol having a transmission symbol corresponding to the remaining bit value of the source bit sequence at a corresponding symbol position and inputs the symbol sequence to the prefix addition unit, and the prefix addition unit is a block obtained by dividing the symbol sequence You may add a prefix to the beginning of
  • the modulation unit may generate a symbol string in which the values of symbols other than transmission symbols are zero.
  • the receiving apparatus may further include a demodulating unit that demodulates the source bit string based on the transmission symbol and the position of the transmission symbol for each sub-block in the reception data.
  • the transmission apparatus includes: an RSC encoder that adds an RSC code to a source bit string indicating information to be transmitted; a plurality of modulation units that generate a symbol string corresponding to an input bit string; and a source bit string obtained by adding an RSC code to the RSC encoder
  • Each of the bits is assigned to one of a plurality of modulation units and is input, and a combining unit that combines the symbol sequences generated by the plurality of modulation units.
  • the plurality of modulation units have different time intervals.
  • the allocating unit controls the ratio of the number of bits input to each modulation unit based on the coding rate in the RSC encoder based on the coding rate in the RSC encoder. Good.
  • the allocating unit is configured so that an outer EXIT curve corresponding to the coding rate of the RSC encoder and an inner EXIT curve obtained by combining a plurality of individual EXIT curves corresponding to the plurality of modulation units are equal to or less than a predetermined interval.
  • the ratio of the number of bits may be controlled.
  • the allocation unit counts the number of bits so that the value of the output mutual information amount of the inner EXIT curve is larger than the value of the input mutual information amount of the outer EXIT curve over the entire range of the input mutual information amount of the inner EXIT curve. The ratio may be controlled.
  • the plurality of modulation units divide the input bit string into a plurality of sub-blocks having a predetermined length, and the bit string of each sub-block is left at a symbol position corresponding to a partial bit value of the bit string. Including two or more modulation units that convert to a symbol string having transmission symbols corresponding to the bit values of the sub-blocks in the two or more modulation units.
  • a transmitting apparatus or a receiving apparatus in the first aspect is provided.
  • a program that causes a computer to function as the transmission device or the reception device of the second aspect.
  • FIG. 4 is a diagram illustrating a configuration example of an interference removal unit 36.
  • FIG. It is a figure explaining the concept of FTN transmission.
  • FIG. 6 is a diagram for explaining the operation of the transmission device 10. 6 is a diagram for explaining the operation of the receiving device 30.
  • FIG. 2 is a diagram showing an outline of an equivalent channel matrix H.
  • FIG. 6 is a diagram illustrating an operation example of the transmission device 10.
  • FIG. 6 is a diagram illustrating an operation example of the reception device 30.
  • BER bit error rate
  • SNR signal to noise ratio
  • FIG. 3 is a diagram illustrating another configuration example of the communication system 100.
  • FIG. 15 shows an example of an EXIT chart in the receiving apparatus 30 shown in FIG. 14. 2 shows an example of a hardware configuration of a computer 1900.
  • FIG. 1 is a diagram illustrating a configuration example of a communication system 100 according to an embodiment of the present invention.
  • the communication system 100 includes a transmission device 10 and a reception device 30.
  • FTN transmission transmitting transmission data at a time interval shorter than that of Nyquist rate.
  • FTN transmission causes intersymbol interference in transmission data.
  • symbol interference in this specification means interference caused by FTN transmission, and unless otherwise specified, is a symbol due to the effects of frequency selective fading and delay spread in the channel. Interference is not included.
  • the receiving device 30 receives the transmission data transmitted by the transmitting device 10 via the channel 20.
  • the channel 20 in this example is a radio channel.
  • Receiving device 30 demodulates received data by removing intersymbol interference caused by transmitting device 10 performing FTN transmission. Thereby, a high transmission rate is realized without expanding the bandwidth of the communication system 100. A method for removing intersymbol interference will be described later.
  • the receiving apparatus 30 may remove intersymbol interference caused by frequency selective fading in a channel in addition to intersymbol interference caused by FTN transmission.
  • the transmission apparatus 10 of this example includes a modulation unit 12, a prefix addition unit 14, a transmission filter 16, and a transmission unit 18.
  • the receiving device 30 includes a receiving unit 32, a prefix removing unit 34, an interference removing unit 36, and a demodulating unit 38. The function of each component will be described later. In the present embodiment, a case where each transmitting / receiving apparatus has one antenna and performs single carrier transmission will be described, but each transmitting / receiving apparatus may have a plurality of antennas.
  • Communication system 100 may be a system that performs multicarrier transmission.
  • FIG. 2 is a diagram illustrating a configuration example of the interference removing unit 36.
  • the interference removal unit 36 converts each reception block from which the prefix has been removed into a frequency domain signal, multiplies the frequency component for each frequency component, and then inversely converts the signal into a time domain signal.
  • the interference removal unit 36 of this example includes a Fourier transform unit 40, a channel matrix calculation unit 42, a weight coefficient multiplication unit 44 and a Fourier inverse transform unit 46. The function of each component will be described later.
  • FIG. 3 is a diagram for explaining the concept of FTN transmission.
  • the frequency bandwidth of the communication system 100 is W.
  • the frequency bandwidth W is determined by, for example, the frequency bandwidth of the transmission filter 16 in the transmission device 10.
  • the symbol time interval is, for example, the interval between the centers of adjacent symbols.
  • each symbol is shown by one mountain-shaped waveform. In this case, no interference occurs between the symbols.
  • the time interval of each symbol is T ⁇ T 0 . For this reason, interference occurs between the symbols.
  • the communication system 100 provides a communication method that easily removes the influence of the inter-symbol interference.
  • the transmission apparatus 10 performs FTN transmission after adding a cyclic prefix (simply referred to as a prefix in this specification) to the head of each block of transmission data.
  • Receiving device 30 calculates an approximate model of intersymbol interference on the assumption that the section where intersymbol interference occurs in each block of received data is shorter than the prefix length. That is, in each block of received data, an approximate model of intersymbol interference occurring in a section shorter than the prefix length is calculated by ignoring intersymbol interference occurring in a section longer than the prefix length. For example, when the prefix includes ⁇ symbols, it is assumed that each symbol included in the block interferes with a symbol separated by ⁇ 1 at the maximum. The approximate model is generated based on at least a time interval at which the transmitter 10 transmits each symbol. Based on the above assumption, the approximate model is represented by a cyclic matrix, and therefore, the influence of intersymbol interference can be easily removed by a simple calculation using the approximate model.
  • FIG. 4 is a diagram for explaining the operation of the transmission apparatus 10.
  • the modulation unit 12 receives the source bit string and generates a plurality of transmission blocks based on a predetermined modulation size M and block size N.
  • the modulation size refers to the number of values that a single complex symbol can take.
  • the block size indicates the number of complex symbols included in one transmission block.
  • FIG. 4 shows a case where the QPSK scheme with a modulation size of 4 is used and the block size is N. In this specification, complex symbols are simply abbreviated as symbols.
  • the modulation unit 12 generates one symbol for every log 2 M bits in the source bit string. Then, one transmission block is generated for every N symbols in the complex symbol sequence. That is, the modulation unit 12 generates a transmission block for each Nlog 2 M bits in the source bit string.
  • the prefix adding unit 14 adds a prefix obtained by copying data having a predetermined length at the end of each block to the head of each transmission block generated by the modulation unit 12.
  • the symbol sequence s of the transmission block is s 0 s 1 ... S N ⁇ 1
  • the prefix length (number of symbols) is ⁇ .
  • the prefix adding unit 14 adds the prefix (s N ⁇ to s N ⁇ 1 ) to the head of the transmission block.
  • the transmission filter 16 limits the bandwidth of the transmission block after the prefix adding unit 14 adds the prefix to a predetermined bandwidth W.
  • the transmission filter 16 is, for example, a raised cosine filter.
  • FIG. 5 is a diagram for explaining the operation of the receiving device 30.
  • the reception unit 32 receives each transmission block transmitted by the transmission unit 18.
  • Each reception block received by the reception unit 32 includes a prefix.
  • the prefix removing unit 34 removes the prefix in each received block. In this example, assuming that timing synchronization is established between the transmission device 10 and the reception device 30, ⁇ symbols are removed from the head of each reception block.
  • n is the symbol number
  • E s is the average power of the symbols included in the transmission signal
  • h (t) is the filter characteristics of the transmitting filter 16
  • s n is the symbol of the transmission block
  • n (t) is the channel 20 Refers to random noise.
  • n (t) is a complex Gaussian distribution noise having an average value of 0 and a variance (noise power) of N 0 .
  • SNR signal to noise ratio
  • Equation (3) indicates the transmitted symbol value
  • the second term indicates intersymbol interference in the block
  • the interference removal unit 36 removes the influence of intersymbol interference caused by FTN transmission.
  • the demodulator 38 demodulates the received block from which the influence of intersymbol interference has been removed.
  • the kth symbol in the received block is expressed by the following equation.
  • L indicates the delay spread in the channel in units of symbol intervals.
  • ql indicates the magnitude of interference of the l-th previous symbol with respect to the k-th symbol.
  • H is an N ⁇ N equivalent channel matrix defined by Equation (5), and indicates intersymbol interference in the received block.
  • h k represents the k-th column component of the equivalent channel matrix H.
  • the equivalent channel matrix H becomes a circulant matrix by assuming that the range in which intersymbol interference occurs is ⁇ .
  • FIG. 6 is a diagram showing an outline of the equivalent channel matrix H.
  • the horizontal direction in FIG. 6 corresponds to the row direction of the equivalent channel matrix H, and the vertical direction corresponds to the column direction.
  • the interval assumed as the range in which intersymbol interference occurs does not have to be the same as the prefix length ⁇ .
  • a section shorter than the prefix length ⁇ may be assumed as a range in which symbol interference occurs.
  • the number of h (x) included in each row of the equivalent channel matrix H is less than ⁇ .
  • the channel matrix calculation unit 42 of this example calculates an equivalent channel matrix H based on the time interval T at which the transmission unit 18 outputs each symbol and the filter coefficient h (x) of the transmission filter 16.
  • These pieces of information may be stored in advance in the channel matrix calculation unit 42, or may be transmitted from the transmission device 10 to the channel matrix calculation unit 42. The transmission of the information may be performed prior to transmission of transmission data or may be performed simultaneously with the transmission data.
  • the interference removal unit 36 removes the influence of intersymbol interference specified by the equivalent channel matrix H from the reception block.
  • the interference removal unit 36 of this example converts the received block into a frequency domain signal, and removes the influence of intersymbol interference by calculation in the frequency domain.
  • the Fourier transform unit 40 performs fast Fourier transform on the received block from which the prefix has been removed, and transforms the received block into a frequency domain signal.
  • the FFT size in the Fourier transform unit 40 of this example is the same as the block length N.
  • the FFT size refers to the number of frequency bins in the spectrum.
  • Non-Patent Documents 3 and 4 equalization is performed in the time domain, but the amount of calculation increases geometrically as intersymbol interference (channel tap length) increases. For this reason, it is difficult to demodulate in real time in a high-speed communication environment using FTN.
  • the weight coefficient multiplication unit 44 multiplies each frequency component of the reception block by a weight coefficient corresponding to the equivalent channel matrix H to remove intersymbol interference.
  • a method of calculating the weight coefficient will be described using the following formulas (6) to (11).
  • the equivalent channel matrix H is a cyclic matrix, it is expressed by the following equation by eigenvalue decomposition.
  • Q is a discrete Fourier transform matrix
  • ⁇ is a diagonal matrix in which the i-th element is represented by the eigenvalue ⁇ (i, i) of the equivalent channel matrix H.
  • Q H is a conjugate transpose matrix of Q and corresponds to the inverse Fourier transform operation.
  • the reception block y f converted to the frequency domain is expressed by the following equation using Q and ⁇ shown in equation (6).
  • s f represents a transmission block converted into the frequency domain
  • n f represents a noise component converted into the frequency domain.
  • Weight coefficient multiplication unit 44 from the reception blocks y f, to recover the transmitted block s ⁇ the time domain.
  • the transmission block s ⁇ in the time domain is expressed by the following equation.
  • Weight coefficient multiplication unit 44 based on the equivalent channel matrix H, and calculate the diagonal matrix W satisfying the relation of equation (10), multiplying the received block y f.
  • Each element of the diagonal matrix W ⁇ (i, i) is an example of the weight coefficients to be multiplied to each frequency component of the received block y f.
  • the noise component n f is zero
  • the diagonal matrix W is an inverse matrix of the diagonal matrix ⁇ .
  • each element of the diagonal matrix W is calculated by the least square error method (MMSE method) as shown in the following equation.
  • MMSE method least square error method
  • Weight coefficient multiplication unit 44 the calculated diagonal matrix W, to multiply the received block y f.
  • the Fourier inverse transform unit 46 inversely transforms the reception block Wy f in the frequency domain multiplied by the weight coefficient into a time domain signal. Processing in the inverse Fourier transform unit 46 corresponds to the process of multiplying the Q H in the formula (10).
  • the transmission rate in the communication system 100 is given by Expression (1).
  • N / (N + ⁇ ) in equation (1) indicates a transmission rate loss due to the addition of a prefix.
  • the addition of the prefix causes a loss in terms of transmission power.
  • the modulation unit 12 selects a block size N that is sufficiently large with respect to the prefix length ⁇ .
  • the block size N is set to several tens to one hundred times the prefix length ⁇ .
  • the prefix adding unit 14 may determine the prefix length ⁇ based on the length N of each block of transmission data.
  • FIG. 7 is a diagram illustrating an operation example of the transmission device 10.
  • the transmission apparatus 10 receives the L-bit source bit string B.
  • the modulation unit 12 divides and modulates the source bit string B into transmission blocks including N symbols.
  • the prefix adding unit 14 adds a prefix to each transmission block.
  • the transmission filter 16 limits the band of each transmission block.
  • the transmission unit 18 performs FTN transmission of each transmission block.
  • the prefix adding unit 14 may adjust the prefix length ⁇ in accordance with the degree of inter-symbol interference caused by FTN transmission.
  • the degree of intersymbol interference refers to the maximum value of the symbol interval at which intersymbol interference that cannot be ignored, for example.
  • the prefix adding unit 14 may determine the prefix length ⁇ based on the symbol interval in the transmission unit 18. The shorter the symbol interval, the greater the degree of intersymbol interference, so the prefix adding unit 14 increases the prefix length ⁇ .
  • the prefix adding unit 14 may determine the prefix length ⁇ based on the filter characteristics of the transmission filter 16. For example, the prefix length ⁇ is determined based on the roll-off coefficient of the transmission filter 16. Since the degree of intersymbol interference increases as the roll-off coefficient decreases, the prefix adding unit 14 increases the prefix length ⁇ .
  • FIG. 8 is a diagram illustrating an operation example of the receiving device 30.
  • the reception unit 32 samples the reception signal at a period T to generate a reception block.
  • the prefix removal unit 34 removes the prefix from each received block.
  • the channel matrix calculation unit 42 calculates an equivalent channel matrix H based on the symbol transmission interval T and the filter coefficient h in the transmission apparatus 10.
  • the channel matrix calculation unit 42 or the weight coefficient multiplication unit 44 further performs eigenvalue decomposition on the equivalent channel matrix H to further calculate matrices Q and ⁇ .
  • the Fourier transform unit 40 performs fast Fourier transform on the received block.
  • the weight coefficient multiplication unit 44 calculates the weight coefficient ⁇ (i, i) based on each element ⁇ (i, i) of the matrix ⁇ using Expression (11).
  • the weight coefficient multiplication unit 44 multiplies the frequency domain reception block by the weight coefficient. This removes intersymbol interference ( ⁇ ) from the received block.
  • the Fourier inverse transform unit 46 inversely transforms the reception block from which the intersymbol interference is removed into a time domain signal. Thereby, the transmission block which reduced the influence of the intersymbol interference by FTN transmission is acquired.
  • the demodulator 38 demodulates the time domain signal output from the inverse Fourier transform unit 46. As a result, the influence of intersymbol interference caused by FTN transmission can be reduced with a small amount of computation on the receiving side.
  • the fast Fourier transform of the reception block can be realized by N 2 complex multiplications.
  • the weight coefficient shown in the equation (11) can be calculated by 4N real number multiplications.
  • the multiplication of equation (10) can be realized by 2N real number multiplications.
  • the weight coefficient multiplication unit 44 may correct the random noise magnitude N 0 superimposed on the reception block based on the symbol interval T in the transmission unit 18 to remove intersymbol interference.
  • the weight coefficient multiplication unit 44 corrects N 0 in Equation (11) and calculates each weight coefficient ⁇ .
  • the weight coefficient multiplier 44 increases N 0 as the degree of intersymbol interference increases.
  • the weight coefficient multiplication unit 44 may increase N 0 as the symbol interval T decreases.
  • the weight coefficient multiplication unit 44 corrects N 0 based on the following equation.
  • 2 represents an estimation error of the equivalent channel matrix H on the vertical axis of FIG.
  • FIGS. 9 to 12 show simulation results for evaluating the characteristics of the communication system 100.
  • FIG. The simulation conditions are as follows.
  • FDE-MMSE frequency domain equivalent-least square error method, Equation 10.
  • FIG. 9 is a diagram showing a bit error rate (BER) with respect to a signal-to-noise ratio (SNR).
  • the modulation method was PSK (BPSK).
  • ⁇ was set to 0.7, and the prefix length was changed between 1 and 20.
  • the transmission rate R according to the equation (1) is 1.43.
  • the SNR is defined by E s / N 0 .
  • the BER is improved by increasing the prefix length ⁇ .
  • FIG. 10 is a diagram showing the magnitude of the estimation error of the equivalent channel matrix H with respect to the pack coefficient ⁇ .
  • the equivalent channel matrix H is calculated on the assumption that intersymbol interference occurs only within the range of ⁇ .
  • the error for the matrix calculated without making the above assumption is calculated.
  • the estimation error increases as the pack coefficient ⁇ decreases.
  • the prefix length ⁇ preferably has such a size that the estimation error is sufficiently small.
  • FIG. 11 is a diagram showing the SNR with respect to the pack coefficient ⁇ .
  • BER 10 ⁇ 5 .
  • FIG. 12 is a diagram illustrating a result of comparison between a transmission / reception method (FDE-FTN) in the communication system 100 and a conventional transmission / reception method (No ISI, ML Limit).
  • R in FIG. 12 is the transmission rate of equation (1), and indicates a relative value.
  • the transmission / reception method of the communication system 100 shows a lower BER than the conventional transmission / reception method.
  • the difference becomes more significant as the transmission rate increases. That is, according to the communication system 100, communication at a high transmission rate can be easily realized.
  • High-speed FTN communication can be realized with a realistic reception calculation amount.
  • the concept of FTN communication itself has been known, but complicated operations are required on the receiving side, and FTN communication cannot be realized on a realistic receiving device scale.
  • the communication system 100 of this example enables high-speed FTN communication on a realistic device scale for the first time, and a dramatic increase in transmission rate can be expected.
  • Communication system 100 is not limited to a wireless communication system.
  • the present invention can be applied to any band-limited communication system such as optical fiber communication and satellite communication.
  • Non-Patent Document 5 discloses signal equivalence using a cyclic prefix.
  • Non-Patent Document 5 is to remove intersymbol interference due to frequency selective fading in the channel, and does not suggest any removal of intersymbol interference due to FTN transmission.
  • the equivalent method is applied to FTN transmission, no specific application method is suggested, such as what parameters should be used by the receiving side to execute the equivalent processing. For this reason, the transmission rate cannot be improved as in the communication system 100.
  • FIG. 13 is a diagram illustrating an operation example of the modulation unit 12 and the prefix addition unit 14.
  • the modulation unit 12 of this example receives a source bit string indicating information to be transmitted.
  • the modulation unit 12 divides the source bit string into a plurality of sub-blocks having a predetermined length.
  • the length indicates the number of bits included in the sub-block.
  • the source bit string is divided into sub-blocks each having a length of 6 bits. Each sub-block has the same length.
  • the modulation unit 12 uses a part of the bit values of the source bit string as symbol position data and converts the remaining bit values into transmission symbols S for each sub-block.
  • the modulation unit 12 of this example converts the first 4 bits of each sub-block into a transmission symbol S and uses the remaining 2 bits as symbol position data.
  • the modulation unit 12 converts the source bit string into a symbol string based on the transmission symbol S and symbol position data of each sub-block. Specifically, a symbol string is generated in which transmission symbols S of each subblock are arranged at symbol positions corresponding to the symbol position data of each subblock. Each sub-block in the symbol string has the number of symbols corresponding to the number of bits of the symbol position data. That is, if the number of bits of the symbol position data is v, each sub-block length is 2 ⁇ v symbol intervals. Thereby, a different symbol position is assigned to each bit pattern of the symbol position data.
  • the first, second, third, and fourth symbol positions are assigned to the bit patterns 00, 01, 10, and 11 of the symbol position data.
  • the symbol position data of sub-block 0 in this example is 01
  • transmission symbol S 0 is the second symbol in sub-block 0.
  • the values of symbols other than the transmission symbol S in the symbol string are set to predetermined constant values.
  • the values of symbols other than the transmission symbol S are preferably zero.
  • the modulation unit 12 divides the symbol sequence into N symbols, and generates the transmission block described with reference to FIG.
  • the modulation unit 12 in this example divides every N symbols, including symbols other than the transmission symbol S (in this example, symbols having a value of 0).
  • the modulation unit 12 sets sub-block 0 to sub-block 2 as one transmission block.
  • the boundary of the transmission block may or may not coincide with the boundary of the sub-block.
  • the modulation unit 12 inputs a transmission block obtained by dividing the symbol string to the prefix addition unit 14.
  • the prefix adding unit 14 adds a prefix to the head of each transmission block.
  • the length of the prefix is 3 symbols.
  • the transmission symbols S are arranged at positions corresponding to the symbol position data, the average interval of the transmission symbols S can be widened as compared with the case where the transmission symbols S are arranged continuously. For this reason, interference between transmission symbols can be reduced. Therefore, even if the transmission rate in FTN transmission is increased, interference between transmission symbols can be suppressed.
  • the symbol position data information can be decoded from the position of the received transmission symbol S.
  • the symbols interval T in this example is not the interval between the transmission symbols S but the interval between symbols including symbols other than the transmission symbols S.
  • the symbol interval T indicates an interval between the transmission symbol S and a symbol having a value of 0.
  • the demodulator 38 in the receiving device 30 divides the symbol string in the received data into a plurality of sub-blocks. The length of the sub-block may be notified from the transmission device 10 to the reception device 30.
  • the demodulator 38 demodulates the original source bit string based on the transmission symbol S in each sub-block and the position of the transmission symbol S. The relationship between the position of the transmission symbol S and the bit pattern of the original symbol position data may be notified from the transmission device 10 to the reception device 30.
  • FIG. 14 is a diagram illustrating another configuration example of the communication system 100.
  • the transmission unit 18, the channel 20, and the reception unit 32 are omitted.
  • the transmission apparatus 10 includes an RSC encoder 50, a first interleaver 52, an allocation unit 54, a plurality of URC encoders 56, a plurality of second interleavers 58, a plurality of FTN sub-encoders 60, and a combining unit 62.
  • the receiving device 30 also includes an assigning unit 64, a plurality of FTN sub-decoders 66, a plurality of third interleavers 68, a plurality of URC decoders 70, a combining unit 72, a fourth interleaver 74, and an RSC decoder 76.
  • the RSC encoder 50 adds an RSC (Recursive Systemical Convolutional) code, which is an error correction code, to a source bit string indicating information to be transmitted.
  • RSC Recursive Systemical Convolutional
  • the ratio between the number of bits of the original information to which the RSC encoder 50 adds the RSC code and the total number of bits after the RSC code is added is defined as the coding rate in the RSC encoder 50.
  • the RSC encoder 50 can be replaced with an arbitrary convolutional code encoder.
  • the first interleaver 52 interleaves the bit string output from the RSC encoder 50.
  • interleaving refers to processing for rearranging the order of bits.
  • the allocation unit 54 allocates and inputs each bit of the source bit string to which the RSC code output from the first interleaver 52 is added to one of the plurality of URC encoders 56.
  • the allocation unit 54 inputs each bit to one of the URC encoders 56 so that the ratio of the number of bits input to each URC encoder 56 becomes a predetermined ratio.
  • the plurality of URC encoders 56 add a URC (Unity Rate Convolutional) code, which is an error correction code, to the input bit string.
  • the plurality of second interleavers 58 are provided one-on-one with respect to the plurality of URC encoders 56. Each second interleaver 58 interleaves the bit string output from the corresponding URC encoder 56.
  • the plurality of FTN sub-encoders 60 are provided one-on-one with respect to the plurality of second interleavers 58. Each FTN sub-encoder 60 generates a symbol string corresponding to the bit string input from the corresponding second interleaver 58. Each FTN sub-encoder 60 functions as the modulation unit 12, the prefix addition unit 14, and the transmission filter 16 described with reference to FIGS. However, each FTN sub-encoder 60 has different characteristics.
  • the plurality of FTN sub-encoders 60 include two or more FTN sub-encoders 60 that generate symbol sequences for transmitting symbols at different time intervals T, respectively.
  • the prefix length in each FTN sub-encoder 60 is different.
  • the symbol sequence generated by each FTN sub-encoder 60 is transmitted by the transmission unit 18 at a corresponding time interval T.
  • the plurality of FTN sub-encoders 60 may include two or more FTN sub-encoders 60 having different sub-block lengths described with reference to FIG. That is, the average interval of the transmission symbol S is different in each FTN sub-encoder 60.
  • the plurality of FTN sub-encoders 60 may include two or more FTN sub-encoders 60 having different roll-off rates ⁇ .
  • the plurality of FTN sub-encoders 60 include two or more FTN sub-encoders 60 having different parameters in the modulation unit 12, the prefix addition unit 14, and the transmission filter 16 described with reference to FIGS. Good. Further, in the plurality of FTN sub-encoders 60, any of the parameters in the modulation unit 12, the prefix addition unit 14, and the transmission filter 16 may be variable.
  • the synthesizing unit 62 synthesizes the symbol sequences output from the plurality of FTN sub-encoders 60 and transmits them to the transmitting unit 18.
  • the combining unit 62 may combine the symbol sequences output from the plurality of FTN sub-encoders 60 in order.
  • the receiving device 30 decodes the transmission data transmitted by the transmitting device 10.
  • the receiving device 30 of this example includes components corresponding to the respective components in the transmitting device 10 and performs inverse conversion of processing of each component in the transmitting device 10. Information such as a prefix length necessary for reverse conversion is notified from the transmission device 10 to the reception device 30.
  • the receiving device 30 passes processing results between the outer configuration and the inner configuration.
  • the outer configuration and the inner configuration further process information based on the processing result of the other party and transmit the processing result to the other party. By repeating such processing, the accuracy of decoding received data is improved.
  • the iterative process is described in the following document, for example.
  • the allocation unit 64 inputs the symbol string of the received data received from the reception unit 32 to each FTN sub-decoder 66 at a rate corresponding to the ratio of the number of bits in the allocation unit 54.
  • the plurality of FTN sub-decoders 66 correspond one-to-one with the plurality of FTN sub-encoders 60.
  • Each FTN sub-decoder 66 performs inverse conversion of processing in the corresponding FTN sub-encoder 60.
  • Each FTN sub-decoder 66 has functions of a prefix removal unit 34, an interference removal unit 36, and a demodulation unit 38.
  • the plurality of third interleavers 68 correspond one-to-one with the plurality of FTN sub-decoders 66.
  • Each third interleaver 68 transmits information to and from the corresponding FTN sub-decoder 66 and URC decoder 70.
  • the third interleaver 68 functions as a deinterleaver that performs a reverse conversion to the second interleaver 58.
  • the second interleaver 58 functions as an interleaver.
  • the plurality of URC decoders 70 correspond one-to-one with the plurality of third interleavers 68. Each URC decoder 70 corrects an error in the bit string based on the URC code.
  • the synthesizer 72 synthesizes the bit strings output from the plurality of URC decoders. Further, when the combining unit 72 receives information from the outer fourth interleaver 74, the combining unit 72 inputs each information to the corresponding URC decoder 70.
  • the URC decoder 70 and the FTN sub-decoder 66 process the received data again based on information from the outside. Further, output information is exchanged between URC decoder 70 and FTN subdecoder 66 a predetermined number of times, and decoding is performed.
  • the fourth interleaver 74 transmits information between the combining unit 72 and the RSC decoder 76. Similarly to the third interleaver 68, the fourth interleaver 74 functions as both a deinterleaver and an interleaver.
  • the RSC decoder 76 corrects an error in the bit string using the RSC code included in the input bit string.
  • the assigning unit 54 controls the ratio of the number of bits assigned to each URC encoder 56 so that the decoding of the received data in the receiving device 30 is optimized.
  • the optimal bit number ratio can be analyzed using an EXIT (EXTrinsic Information Transfer) chart.
  • FIG. 15 shows an example of an EXIT chart in the receiving apparatus 30 shown in FIG.
  • the horizontal axis in FIG. 15 indicates the input mutual information amount IA received from the configuration outside the receiving device 30 by the configuration inside the receiving device 30 (FTN subdecoder 66 and URC encoder 56), and the vertical axis indicates the receiving device 30.
  • the output mutual information IE to be output to the configuration outside the receiving apparatus 30 is shown in the inner configuration of FIG.
  • the horizontal axis also corresponds to the output mutual information amount IE in the configuration outside the receiving apparatus 30 (RSC decoder 76), and the vertical axis also corresponds to the input mutual information amount IA in the outer configuration.
  • a mutual information amount value of 1 indicates that the transmission data information has been completely decoded, and a value of 0 indicates that the information has not been decoded at all.
  • the solid line is an inner EXIT curve showing the relationship between the input mutual information amount and the output mutual information amount in the configuration inside the receiving device 30.
  • a broken line is an outer EXIT curve showing the relationship between the input mutual information amount and the output mutual information amount in the configuration outside the receiving apparatus 30.
  • a line plotted with a circle is an individual EXIT curve showing the relationship between the input mutual information amount and the output mutual information amount in each set of the FTN sub-decoder 66 and the URC encoder 56.
  • the inner EXIT curve is a ratio of symbols inputted to the respective FTN sub-decoders 66 (that is, a ratio of bits inputted by the allocation unit 54 to the URC encoder 56 and the FTN sub-encoder 60). It is a curve weighted and added by.
  • the output mutual information IE is non-zero (about 0.2 in FIG. 15) even if the input mutual information IA from the outer configuration is zero. .
  • the output mutual information IE inside the receiving device 30 becomes the input mutual information IA having a configuration outside the receiving device 30.
  • the configuration outside the receiving device 30 outputs output mutual information IE corresponding to the input mutual information IA (about 0.1 in FIG. 15).
  • the output mutual information IE of the configuration outside the receiving device 30 becomes the input mutual information IA of the configuration inside the receiving device 30.
  • the internal configuration of the receiving device 30 outputs output mutual information IE (about 0.28 in FIG. 15) corresponding to the input mutual information IA. By repeating such processing, the mutual information amount gradually increases.
  • the inner EXIT curve and the outer EXIT curve are preferably as close as possible. A state where the two curves deviate indicates that the transmission data is given more redundancy than necessary. This causes a loss in transmission efficiency.
  • the value of the output mutual information amount IE of the inner EXIT curve is larger than the value of the input mutual information amount IA of the outer EXIT curve over the entire range of the input mutual information amount IA of the inner EXIT curve of the receiving device 30. preferable. Thereby, the mutual information amount can be set to 1 by repeating the mutual processing in the configuration inside and outside the receiving apparatus 30.
  • the outer EXIT curve changes depending on the coding rate in the RSC encoder 50.
  • the allocation unit 54 of this example controls the ratio of the number of bits input to each URC encoder 56 and FTN sub-encoder 60 based on the coding rate in the RSC encoder 50. Thereby, the weight of the individual EXIT curve can be changed according to the change of the outer EXIT curve, and the inner EXIT curve approximated to the outer EXIT curve can be generated.
  • the assigning unit 54 is given in advance an outer EXIT curve for each coding rate. Further, each EXIT curve is given to the allocation unit 54 in advance.
  • the assigning unit 54 controls the ratio of the number of bits input to each URC encoder 56 so that the outer EXIT curve and the inner EXIT curve are equal to or less than a predetermined interval.
  • the interval may be an interval in the vertical axis direction at a predetermined value on the horizontal axis of the EXIT chart.
  • the ratio of the number of bits input to each URC encoder 56 is set so that the difference between the outer EXIT curve and the inner EXIT curve in the vertical axis direction is 0.05 or less. You may control.
  • the interval may be given by the area of a region sandwiched between the outer EXIT curve and the inner EXIT curve in the EXIT chart.
  • the assigning unit 54 has a value of the output mutual information amount IE of the inner EXIT curve larger than a value of the input mutual information amount IA of the outer EXIT curve over the entire range of the input mutual information amount IA of the inner EXIT curve.
  • the upper limit of the mutual information amount can be set to 1.
  • the allocating unit 54 may further control the ratio of the number of bits input to each URC encoder 56 based on the S / N ratio in the channel 20.
  • the allocation unit 54 is given in advance an individual EXIT curve for each S / N ratio.
  • the transmitting apparatus 10 may transmit a pilot signal for measuring the S / N ratio to the receiving apparatus 30 before transmitting a signal to be transmitted.
  • the receiving device 30 measures the S / N ratio in the channel 20 based on the received known pilot signal.
  • the receiving device 30 notifies the transmitting device 10 of the S / N ratio. With such a configuration, it is possible to optimize a transmission signal by optimizing a combination of parameters in FTN transmission.
  • FIG. 16 shows an example of the hardware configuration of the computer 1900.
  • the computer 1900 functions as at least a part of the transmission device 10 described with reference to FIGS. 1 to 15 or at least a part of the reception device 30.
  • Two computers 1900 may function as at least a part of the communication system 100.
  • the computer 1900 includes a CPU peripheral unit having a CPU 2000, a RAM 2020, a graphic controller 2075, and a display device 2080 that are connected to each other by a host controller 2082, and a communication interface 2030 that is connected to the host controller 2082 by an input / output controller 2084.
  • An input / output unit having a hard disk drive 2040 and a CD-ROM drive 2060, and a legacy input / output unit having a ROM 2010, a flexible disk drive 2050, and an input / output chip 2070 connected to the input / output controller 2084.
  • the host controller 2082 connects the RAM 2020 to the CPU 2000 and the graphic controller 2075 that access the RAM 2020 at a high transfer rate.
  • the CPU 2000 operates based on programs stored in the ROM 2010 and the RAM 2020 and controls each unit.
  • the graphic controller 2075 acquires image data generated by the CPU 2000 or the like on a frame buffer provided in the RAM 2020 and displays it on the display device 2080.
  • the graphic controller 2075 may include a frame buffer for storing image data generated by the CPU 2000 or the like.
  • the input / output controller 2084 connects the host controller 2082 to the communication interface 2030, the hard disk drive 2040, and the CD-ROM drive 2060, which are relatively high-speed input / output devices.
  • the communication interface 2030 communicates with other devices via a network.
  • the hard disk drive 2040 stores programs and data used by the CPU 2000 in the computer 1900.
  • the CD-ROM drive 2060 reads a program or data from the CD-ROM 2095 and provides it to the hard disk drive 2040 via the RAM 2020.
  • the ROM 2010, the flexible disk drive 2050, and the relatively low-speed input / output device of the input / output chip 2070 are connected to the input / output controller 2084.
  • the ROM 2010 stores a boot program that the computer 1900 executes at startup and / or a program that depends on the hardware of the computer 1900.
  • the flexible disk drive 2050 reads a program or data from the flexible disk 2090 and provides it to the hard disk drive 2040 via the RAM 2020.
  • the input / output chip 2070 connects the flexible disk drive 2050 to the input / output controller 2084 and inputs / outputs various input / output devices via, for example, a parallel port, a serial port, a keyboard port, a mouse port, and the like. Connect to controller 2084.
  • the program provided to the hard disk drive 2040 via the RAM 2020 is stored in a recording medium such as the flexible disk 2090, the CD-ROM 2095, or an IC card and provided by the user.
  • the program is read from the recording medium, installed in the hard disk drive 2040 in the computer 1900 via the RAM 2020, and executed by the CPU 2000.
  • a program that is installed in the computer 1900 and causes the computer 1900 to function as the transmission device 10 or the reception device 30 works on the CPU 2000 or the like to cause the computer 1900 to function as the transmission device 10 or the reception device 30, respectively.
  • the information processing described in these programs is read by the computer 1900, whereby the modulation unit 12, the prefix addition unit 14, the transmission filter, which are specific means in which the software and the various hardware resources described above cooperate. 16, the transmission unit 18, the reception unit 32, the prefix removal unit 34, the interference removal unit 36, and the demodulation unit 38. Then, the specific transmission device 10 or the reception device 30 corresponding to the purpose of use is constructed by realizing calculation or processing of information according to the purpose of use of the computer 1900 in this embodiment by these specific means. .
  • the CPU 2000 executes a communication program loaded on the RAM 2020 and executes a communication interface based on the processing content described in the communication program.
  • a communication process is instructed to 2030.
  • the communication interface 2030 reads transmission data stored in a transmission buffer area or the like provided on a storage device such as the RAM 2020, the hard disk drive 2040, the flexible disk 2090, or the CD-ROM 2095, and sends it to the network.
  • the reception data transmitted or received from the network is written into a reception buffer area or the like provided on the storage device.
  • the communication interface 2030 may transfer transmission / reception data to / from the storage device by a DMA (direct memory access) method. Instead, the CPU 2000 transfers the storage device or the communication interface 2030 as a transfer source.
  • the transmission / reception data may be transferred by reading the data from the data and writing the data to the communication interface 2030 or the storage device of the transfer destination.
  • the CPU 2000 is all or necessary from among files or databases stored in an external storage device such as a hard disk drive 2040, a CD-ROM drive 2060 (CD-ROM 2095), and a flexible disk drive 2050 (flexible disk 2090).
  • This portion is read into the RAM 2020 by DMA transfer or the like, and various processes are performed on the data on the RAM 2020. Then, CPU 2000 writes the processed data back to the external storage device by DMA transfer or the like.
  • the RAM 2020 and the external storage device are collectively referred to as a memory, a storage unit, or a storage device.
  • the CPU 2000 can also store a part of the RAM 2020 in the cache memory and perform reading and writing on the cache memory. Even in such a form, the cache memory bears a part of the function of the RAM 2020. Therefore, in the present embodiment, the cache memory is also included in the RAM 2020, the memory, and / or the storage device unless otherwise indicated. To do.
  • the CPU 2000 performs various operations, such as various operations, information processing, condition determination, information search / replacement, etc., described in the present embodiment, specified for the data read from the RAM 2020 by the instruction sequence of the program. Is written back to the RAM 2020.
  • the CPU 2000 determines whether or not the various variables shown in the present embodiment satisfy the conditions such as large, small, above, below, equal, etc., compared to other variables or constants.
  • the program branches to a different instruction sequence or calls a subroutine.
  • DESCRIPTION OF SYMBOLS 10 ... Transmission apparatus, 12 ... Modulation part, 14 ... Prefix addition part, 16 ... Transmission filter, 18 ... Transmission part, 20 ... Channel, 30 ... Reception apparatus, 32 ... Receiving part 34 ... Prefix removing part 36 ... Interference removing part 38 ... Demodulating part 40 ... Fourier transforming part 42 ... Channel matrix calculating part 44 ... Weight coefficient multiplying unit, 46 ... Fourier inverse transform unit, 50 ... RSC encoder, 52 ... first interleaver, 54 ... allocation unit, 56 ... URC encoder, 58 ... second Interleaver, 60 ... FTN sub-encoder, 62 ... combining unit, 64 ... assigning unit, 66 ...
  • FTN sub-decoder 68 ... third interleaver, 70 ... URC decoder, 72 ⁇ ⁇ Synthesizer, 74 ... 4th interleaver, 76 ... RSC decoder, 100 ... communication system, 1900 ... computer, 2000 ... CPU, 2010 ... ROM, 2020 ... RAM, 2030: Communication interface, 2040 ... Hard disk drive, 2050 ... Flexible disk drive, 2060 ... CD-ROM drive, 2070 ... I / O chip, 2075 ... Graphic controller, 2080 ..Display device, 2082 ... Host controller, 2084 ... Input / output controller, 2090 ... Flexible disk, 2095 ... CD-ROM

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Abstract

Provided is a band-limited communication system including a transmission device and a reception device, wherein the transmission device is provided with a prefix addition unit for adding, to the head of each of blocks of transmission data, a prefix to which data of a predetermined length at the tail end of each of the blocks is copied, and a transmission unit for transmitting each symbol of the transmission data to which the prefix is added at time intervals shorter than a Nyquist rate corresponding to the band of the communication system, and the reception device is provided with a prefix removal unit for removing the prefix from each of blocks of reception data, and an interference removal unit for removing inter-symbol interference caused by the transmission unit transmitting the symbol at time intervals shorter than the Nyquist rate in each of the blocks from which the prefix has been removed.

Description

通信システム、送信装置、受信装置、通信方法およびプログラムCOMMUNICATION SYSTEM, TRANSMISSION DEVICE, RECEPTION DEVICE, COMMUNICATION METHOD, AND PROGRAM
　本発明は、通信システム、送信装置、受信装置、通信方法およびプログラムに関する。 The present invention relates to a communication system, a transmission device, a reception device, a communication method, and a program.
　帯域制限された通信システムでは、シンボル間干渉を生じさせない各シンボルの送信間隔が、利用可能な周波数帯域Ｗにより定まるナイキストレートで与えられる（例えば、特許文献１参照）。ナイキストレートより長い時間間隔で各シンボルを送信することで、送信シンボル間で干渉が生じないことを前提とした単純な受信装置を用いることができる。これに対して、ナイキストレートより短い時間間隔で各シンボルを送信するＦＴＮ（Ｆａｓｔｅｒ－Ｔｈａｎ－Ｎｙｑｕｉｓｔ）方式も考案されている（例えば、非特許文献２参照）。 In a band-limited communication system, a transmission interval of each symbol that does not cause intersymbol interference is given by a Nyquist rate determined by an available frequency band W (for example, see Patent Document 1). By transmitting each symbol at a time interval longer than that of the Nyquist rate, it is possible to use a simple receiving device on the assumption that no interference occurs between transmission symbols. On the other hand, an FTN (Faster-Than-Nyquist) system that transmits each symbol at a time interval shorter than that of the Nyquist rate has also been devised (for example, see Non-Patent Document 2).
　ＦＴＮ方式では、通信システムが利用可能な帯域を増大させることなく、送信レートを向上させることができる。一方、受信側では、シンボル間干渉の影響を受けるので、復調のための演算量が大幅に増加する。近年の信号処理能力の向上に合わせて、いくつかのＦＴＮ復調アルゴリズム（時間空間等化アルゴリズム）が考案されている（例えば、非特許文献３、４参照）。非特許文献３では、シンボル間干渉が生じた受信データを畳み込み符号とみなしてビタビアルゴリズムを適用する。非特許文献４では、ＳＩＣ（ｓｕｃｃｅｓｓｉｖｅ　ｉｎｔｅｒｆｅｒｅｎｃｅ　ｃａｎｃｅｌｌａｔｉｏｎ）に基づく繰り返し信号を利用している。また、シンボル間干渉を送信側で補償するプリコーディングアルゴリズム（例えば、特許文献１参照）、および、ＦＴＮ送受信機に適したタイミング同期アルゴリズム（例えば、特許文献２参照）が開発された。 In the FTN system, the transmission rate can be improved without increasing the bandwidth available for the communication system. On the other hand, since the receiving side is affected by inter-symbol interference, the amount of calculation for demodulation increases significantly. Several FTN demodulation algorithms (time-space equalization algorithms) have been devised in accordance with the recent improvement in signal processing capability (for example, see Non-Patent Documents 3 and 4). In Non-Patent Document 3, the Viterbi algorithm is applied by regarding received data in which intersymbol interference has occurred as a convolutional code. In Non-Patent Document 4, a repetitive signal based on SIC (successive interference cancellation) is used. In addition, a precoding algorithm (see, for example, Patent Document 1) that compensates for inter-symbol interference on the transmission side and a timing synchronization algorithm (for example, see Patent Document 2) suitable for an FTN transceiver have been developed.
　また、信号が伝送するチャネルにおける周波数選択性フェージング等の影響で生じたシンボル間干渉を低減する技術が知られている（例えば、非特許文献５参照）。
　関連する先行技術文献を以下に示す。
　非特許文献１　J. G. Proakis, Digital Communications, 5th ed. McGraw-Hill, New York, 2008. 
　非特許文献２　J. E. Mazo, "Faster-than-Nyquist signaling," Bell System Technical Journal, vol. 54, no. 8, pp. 1451-1462, 1975. 
　非特許文献３　A. D. Liveris and C. N. Georghiades, "Exploiting faster-than-Nyquist signaling," IEEE Transactions on Communications, vol. 51, no. 9, pp. 1502-1511, 2003. 
　非特許文献４　F. Rusek and J. Anderson, "Multistream faster than Nyquist signaling," IEEE Transactions on Communications, vol. 57, no. 5, pp. 1329-1340, May 2009. 
　非特許文献５　林和則　「変復調と等化方式の基礎（Fundamentals of Modulation/Demodulation and Equalization Technologies）」Proc. MWE2004、 pp523-532, 2004.
　非特許文献６　Nan Wu and Lajos Hanzo, "Near-Capacity Irregular-Convolutional-Coding-Aided Irregular Precoded Linear Dispersion Codes" IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 6, JULY 2009.
　特許文献１　欧州特許第２３４２８３２号明細書
　特許文献２　欧州特許第２４３６１４０号明細書 In addition, a technique for reducing intersymbol interference caused by the influence of frequency selective fading in a channel through which a signal is transmitted is known (for example, see Non-Patent Document 5).
Related prior art documents are shown below.
Non-Patent Document 1 J. G. Proakis, Digital Communications, 5th ed. McGraw-Hill, New York, 2008.
Non-Patent Document 2 J. E. Mazo, "Faster-than-Nyquist signaling," Bell System Technical Journal, vol. 54, no. 8, pp. 1451-1462, 1975.
Non-Patent Document 3 A. D. Liveris and C. N. Georghiades, "Exploiting faster-than-Nyquist signaling," IEEE Transactions on Communications, vol. 51, no. 9, pp. 1502-1511, 2003.
Non-Patent Document 4 F. Rusek and J. Anderson, "Multistream faster than Nyquist signaling," IEEE Transactions on Communications, vol. 57, no. 5, pp. 1329-1340, May 2009.
Non-Patent Document 5 Hayashi Kazunori “Fundamentals of Modulation / Demodulation and Equalization Technologies” Proc. MWE2004, pp523-532, 2004.
Non-Patent Document 6 Nan Wu and Lajos Hanzo, "Near-Capacity Irregular-Convolutional-Coding-Aided Irregular Precoded Linear Dispersion Codes" IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 6, JULY 2009.
Patent Document 1 European Patent No. 2342832 Patent Document 2 European Patent No. 2436140 Specification
　しかし、従来のＦＴＮ送受信機においては、受信機における演算負荷が大きかった。 However, in the conventional FTN transceiver, the calculation load on the receiver is large.
　本発明の第１の態様においては、送信装置および受信装置を含む、帯域制限された通信システムであって、送信装置は、送信データの各ブロックの先頭に、各ブロックの最後尾における予め定められた長さのデータをコピーしたプレフィックスを付加するプレフィックス付加部と、プレフィックスが付加された送信データの各シンボルを、通信システムの帯域に応じたナイキストレートよりも短い時間間隔で送信する送信部とを備え、受信装置は、受信データの各ブロックからプレフィックスを除去するプレフィックス除去部と、プレフィックスが除去された各ブロックにおいて、送信部がナイキストレートよりも短い時間間隔でシンボルを送信したことにより生じたシンボル間干渉を除去する干渉除去部とを備える通信システム、および、当該通信システムに係る通信方法を提供する。 According to a first aspect of the present invention, there is provided a band-limited communication system including a transmission device and a reception device, wherein the transmission device is predetermined at the head of each block of transmission data and at the end of each block. A prefix adding unit that adds a prefix obtained by copying the length of data, and a transmission unit that transmits each symbol of the transmission data to which the prefix is added at a time interval shorter than the Nyquist rate according to the communication system band. A prefix removing unit that removes a prefix from each block of received data, and a symbol generated by transmitting a symbol at a time interval shorter than the Nyquist rate in each block from which the prefix is removed. A communication system comprising an interference canceling unit that cancels inter-interference, and To provide a communication method according to the communication system.
　干渉除去部は、受信データの各ブロックにおいて、プレフィックスの長さより長い区間で生じるシンボル間干渉を無視して、プレフィックスの長さ以下の区間で生じるシンボル間干渉を除去してよい。干渉除去部は、送信部における各シンボルの時間間隔に基づいて、受信データからシンボル間干渉を除去してよい。 The interference removal unit may ignore intersymbol interference that occurs in a section longer than the prefix length in each block of received data, and remove intersymbol interference that occurs in a section that is shorter than the prefix length. The interference removal unit may remove intersymbol interference from the received data based on the time interval of each symbol in the transmission unit.
　送信装置は、プレフィックスが付加された送信データの帯域幅を、予め定められた帯域幅に制限して送信部に入力する送信フィルタを更に備え、干渉除去部は、送信フィルタのフィルタ特性に基づいて、受信データからシンボル間干渉を除去してよい。送信装置は、送信部における時間間隔を示す情報を、受信装置に送信してよい。送信装置は、送信フィルタのフィルタ特性を示す情報を、受信装置に送信してよい。 The transmission device further includes a transmission filter that restricts the bandwidth of the transmission data to which the prefix is added to a predetermined bandwidth and inputs the transmission data to the transmission unit, and the interference removal unit is based on the filter characteristics of the transmission filter. Intersymbol interference may be removed from the received data. The transmission device may transmit information indicating the time interval in the transmission unit to the reception device. The transmission device may transmit information indicating the filter characteristics of the transmission filter to the reception device.
　プレフィックス付加部は、送信部における時間間隔に基づいて、プレフィックスの長さを定めてよい。プレフィックス付加部は、送信フィルタのフィルタ特性に基づいて、プレフィックスの長さを定めてよい。プレフィックス付加部は、送信データの各ブロックの長さに基づいてプレフィックスの長さを定めてよい。 The prefix adding unit may determine the prefix length based on the time interval in the transmitting unit. The prefix adding unit may determine the length of the prefix based on the filter characteristics of the transmission filter. The prefix adding unit may determine the length of the prefix based on the length of each block of transmission data.
　干渉除去部は、受信データを周波数領域の信号に変換し、周波数領域においてシンボル間干渉の成分を除去してよい。干渉除去部は、ブロックにおけるシンボル間干渉を示す等価チャネルマトリクスを巡回行列で近似し、受信データの各周波数成分に対して、巡回行列に応じたウェイト係数を乗算してシンボル間干渉を除去してよい。干渉除去部は、送信部における時間間隔に基づいて、受信データに重畳されたランダム雑音の大きさを補正して、シンボル間干渉を除去してよい。 The interference removing unit may convert the received data into a frequency domain signal and remove an intersymbol interference component in the frequency domain. The interference removal unit approximates an equivalent channel matrix indicating intersymbol interference in a block by a cyclic matrix, and multiplies each frequency component of received data by a weight coefficient corresponding to the cyclic matrix to remove intersymbol interference. Good. The interference removal unit may correct the magnitude of random noise superimposed on the received data based on the time interval in the transmission unit to remove intersymbol interference.
　送信装置は、送信すべき情報を示すソースビット列を受け取り、ソースビット列を予め定められた長さの複数のサブブロックに分割し、各サブブロックのソースビット列を、ソースビット列の一部のビット値に対応するシンボル位置に、ソースビット列の残りのビット値に応じた送信シンボルを有するシンボル列に変換して、プレフィックス付加部に入力する変調部を更に備え、プレフィックス付加部は、シンボル列を分割したブロックの先頭に、プレフィックスを付加してよい。変調部は、送信シンボル以外のシンボルの値が零であるシンボル列を生成してよい。受信装置は、受信データにおける各サブブロックについて、送信シンボルと、送信シンボルの位置とに基づいて、ソースビット列を復調する復調部を更に備えてよい。 The transmitting device receives a source bit string indicating information to be transmitted, divides the source bit string into a plurality of sub-blocks having a predetermined length, and converts the source bit string of each sub-block into a partial bit value of the source bit string. The block further includes a modulation unit that converts a symbol symbol having a transmission symbol corresponding to the remaining bit value of the source bit sequence at a corresponding symbol position and inputs the symbol sequence to the prefix addition unit, and the prefix addition unit is a block obtained by dividing the symbol sequence You may add a prefix to the beginning of The modulation unit may generate a symbol string in which the values of symbols other than transmission symbols are zero. The receiving apparatus may further include a demodulating unit that demodulates the source bit string based on the transmission symbol and the position of the transmission symbol for each sub-block in the reception data.
　送信装置は、送信すべき情報を示すソースビット列にＲＳＣ符号を付加するＲＳＣエンコーダと、入力されるビット列に応じたシンボル列を生成する複数の変調部と、ＲＳＣエンコーダがＲＳＣ符号を付加したソースビット列の各ビットを、複数の変調部のいずれかに割り当てて入力する割り当て部と、複数の変調部が生成したシンボル列を合成する合成部とを有し、複数の変調部は、それぞれ異なる時間間隔でシンボルを送信するためのシンボル列を生成する２以上の変調部を含み、割り当て部は、ＲＳＣエンコーダにおける符号化率に基づいて、それぞれの変調部に入力するビットの個数の比を制御してよい。 The transmission apparatus includes: an RSC encoder that adds an RSC code to a source bit string indicating information to be transmitted; a plurality of modulation units that generate a symbol string corresponding to an input bit string; and a source bit string obtained by adding an RSC code to the RSC encoder Each of the bits is assigned to one of a plurality of modulation units and is input, and a combining unit that combines the symbol sequences generated by the plurality of modulation units. The plurality of modulation units have different time intervals. The allocating unit controls the ratio of the number of bits input to each modulation unit based on the coding rate in the RSC encoder based on the coding rate in the RSC encoder. Good.
　割り当て部は、ＲＳＣエンコーダの符号化率に応じた外側ＥＸＩＴ曲線と、複数の変調部に対応する複数の個別ＥＸＩＴ曲線を合成した内側ＥＸＩＴ曲線とが、予め定められた間隔以下となるように、ビットの個数の比を制御してよい。割り当て部は、内側ＥＸＩＴ曲線の入力相互情報量の全範囲に渡って、内側ＥＸＩＴ曲線の出力相互情報量の値が、外側ＥＸＩＴ曲線の入力相互情報量の値より大きくなるように、ビットの個数の比を制御してよい。 The allocating unit is configured so that an outer EXIT curve corresponding to the coding rate of the RSC encoder and an inner EXIT curve obtained by combining a plurality of individual EXIT curves corresponding to the plurality of modulation units are equal to or less than a predetermined interval. The ratio of the number of bits may be controlled. The allocation unit counts the number of bits so that the value of the output mutual information amount of the inner EXIT curve is larger than the value of the input mutual information amount of the outer EXIT curve over the entire range of the input mutual information amount of the inner EXIT curve. The ratio may be controlled.
　複数の変調部は、入力されたビット列を予め定められた長さの複数のサブブロックに分割し、各サブブロックのビット列を、ビット列の一部のビット値に対応するシンボル位置に、ビット列の残りのビット値に応じた送信シンボルを有するシンボル列に変換する２以上の変調部を含み、２以上の変調部におけるサブブロックの長さが異なってよい。 The plurality of modulation units divide the input bit string into a plurality of sub-blocks having a predetermined length, and the bit string of each sub-block is left at a symbol position corresponding to a partial bit value of the bit string. Including two or more modulation units that convert to a symbol string having transmission symbols corresponding to the bit values of the sub-blocks in the two or more modulation units.
　本発明の第２の態様においては、第１の態様における送信装置、または、受信装置を提供する。本発明の第３の態様においては、コンピュータを、第２の態様の送信装置または受信装置として機能させるプログラムを提供する。 In the second aspect of the present invention, a transmitting apparatus or a receiving apparatus in the first aspect is provided. In a third aspect of the present invention, there is provided a program that causes a computer to function as the transmission device or the reception device of the second aspect.
　なお、上記の発明の概要は、本発明の必要な特徴の全てを列挙したものではない。また、これらの特徴群のサブコンビネーションもまた、発明となりうる。 Note that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.
本発明の実施形態に係る通信システム１００の構成例を示す図である。It is a figure which shows the structural example of the communication system 100 which concerns on embodiment of this invention. 干渉除去部３６の構成例を示す図である。4 is a diagram illustrating a configuration example of an interference removal unit 36. FIG. ＦＴＮ送信の概念を説明する図である。It is a figure explaining the concept of FTN transmission. 送信装置１０の動作を説明する図である。FIG. 6 is a diagram for explaining the operation of the transmission device 10. 受信装置３０の動作を説明する図である。6 is a diagram for explaining the operation of the receiving device 30. FIG. 等価チャネルマトリクスＨの概要を示す図である。2 is a diagram showing an outline of an equivalent channel matrix H. FIG. 送信装置１０の動作例を示す図である。6 is a diagram illustrating an operation example of the transmission device 10. FIG. 受信装置３０の動作例を示す図である。6 is a diagram illustrating an operation example of the reception device 30. FIG. 信号対雑音比（ＳＮＲ）に対するビットエラーレート（ＢＥＲ）を示す図である。It is a figure which shows the bit error rate (BER) with respect to a signal to noise ratio (SNR). パック係数αに対する等価チャネルマトリクスＨの推定誤差の大きさを示す図である。It is a figure which shows the magnitude | size of the estimation error of the equivalent channel matrix H with respect to the pack coefficient (alpha). パック係数αに対するＳＮＲを示す図である。It is a figure which shows SNR with respect to pack coefficient (alpha). 通信システム１００における送受信方式（ＦＤＥ－ＦＴＮ）と、従来の送受信方式（Ｎｏ　ＩＳＩ、ＭＬ　Ｌｉｍｉｔ）とを比較した結果を示す図である。It is a figure which shows the result of having compared the transmission / reception system (FDE-FTN) in the communication system 100, and the conventional transmission / reception system (No ISI, ML Limit). 変調部１２およびプレフィックス付加部１４の動作例を示す図である。6 is a diagram illustrating an operation example of a modulation unit 12 and a prefix addition unit 14. FIG. 通信システム１００の他の構成例を示す図である。3 is a diagram illustrating another configuration example of the communication system 100. FIG. 図１４に示した受信装置３０におけるＥＸＩＴチャートの一例を示す。FIG. 15 shows an example of an EXIT chart in the receiving apparatus 30 shown in FIG. 14. コンピュータ１９００のハードウェア構成の一例を示す。2 shows an example of a hardware configuration of a computer 1900.
　以下、発明の実施の形態を通じて本発明を説明するが、以下の実施形態は請求の範囲にかかる発明を限定するものではない。また、実施形態の中で説明されている特徴の組み合わせの全てが発明の解決手段に必須であるとは限らない。 Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.
　図１は、本発明の実施形態に係る通信システム１００の構成例を示す図である。通信システム１００は、送信装置１０および受信装置３０を備える。送信装置１０は、帯域制限された送信データの各シンボルを、ナイキストレートよりも短い時間間隔で送信する。なお、ナイキストレートにおける各シンボルの時間間隔T０は、T０＝１／（２Ｗ）で与えられる。但し、Ｗは通信システムが利用可能な帯域幅を示す。 FIG. 1 is a diagram illustrating a configuration example of a communication system 100 according to an embodiment of the present invention. The communication system 100 includes a transmission device 10 and a reception device 30. The transmission apparatus 10 transmits each symbol of transmission data whose band is limited at a time interval shorter than that of the Nyquist rate. Note that the time interval T 0 of each symbol in the Nyquist rate is given by T 0 = 1 / (2W). Here, W represents a bandwidth that can be used by the communication system.
　本明細書では、ナイキストレートよりも短い時間間隔で送信データを送信することを、ＦＴＮ送信と称する。ＦＴＮ送信により、送信データにシンボル間干渉が生じる。なお、本明細書における「シンボル間干渉」の用語は、ＦＴＮ送信により生じた干渉を意味しており、特に明示している場合を除き、チャネルにおける周波数選択性フェージングおよびディレイスプレッド等の影響によるシンボル間干渉を含まない。 In this specification, transmitting transmission data at a time interval shorter than that of Nyquist rate is referred to as FTN transmission. FTN transmission causes intersymbol interference in transmission data. Note that the term “intersymbol interference” in this specification means interference caused by FTN transmission, and unless otherwise specified, is a symbol due to the effects of frequency selective fading and delay spread in the channel. Interference is not included.
　受信装置３０は、送信装置１０が送信した送信データを、チャネル２０を介して受信する。本例のチャネル２０は、無線チャネルである。受信装置３０は、送信装置１０がＦＴＮ送信したことにより生じたシンボル間干渉を除去して、受信データを復調する。これにより、通信システム１００の帯域を広げずに、高い送信レートを実現する。シンボル間干渉の除去方法は後述する。なお、受信装置３０は、ＦＴＮ送信により生じるシンボル間干渉に加え、チャネルにおける周波数選択性フェージング等で生じるシンボル間干渉も除去してよい。 The receiving device 30 receives the transmission data transmitted by the transmitting device 10 via the channel 20. The channel 20 in this example is a radio channel. Receiving device 30 demodulates received data by removing intersymbol interference caused by transmitting device 10 performing FTN transmission. Thereby, a high transmission rate is realized without expanding the bandwidth of the communication system 100. A method for removing intersymbol interference will be described later. Note that the receiving apparatus 30 may remove intersymbol interference caused by frequency selective fading in a channel in addition to intersymbol interference caused by FTN transmission.
　本例の送信装置１０は、変調部１２、プレフィックス付加部１４、送信フィルタ１６および送信部１８を備える。また、受信装置３０は、受信部３２、プレフィックス除去部３４、干渉除去部３６および復調部３８を備える。各構成の機能は後述する。本実施形態では、送受信装置がそれぞれ１本のアンテナを持ち、シングルキャリア伝送する場合について述べるが、送受信装置は、それぞれ複数のアンテナを有してよい。また、通信システム１００は、マルチキャリア伝送するシステムであってもよい。 The transmission apparatus 10 of this example includes a modulation unit 12, a prefix addition unit 14, a transmission filter 16, and a transmission unit 18. The receiving device 30 includes a receiving unit 32, a prefix removing unit 34, an interference removing unit 36, and a demodulating unit 38. The function of each component will be described later. In the present embodiment, a case where each transmitting / receiving apparatus has one antenna and performs single carrier transmission will be described, but each transmitting / receiving apparatus may have a plurality of antennas. Communication system 100 may be a system that performs multicarrier transmission.
　図２は、干渉除去部３６の構成例を示す図である。干渉除去部３６は、プレフィックスを除去した各受信ブロックを周波数領域の信号に変換し、周波数成分毎にウェイト係数を乗算した後に時間領域の信号に逆変換する。本例の干渉除去部３６は、フーリエ変換部４０、チャネルマトリクス算出部４２、ウェイト係数乗算部４４およびフーリエ逆変換部４６を有する。各構成の機能は後述する。 FIG. 2 is a diagram illustrating a configuration example of the interference removing unit 36. The interference removal unit 36 converts each reception block from which the prefix has been removed into a frequency domain signal, multiplies the frequency component for each frequency component, and then inversely converts the signal into a time domain signal. The interference removal unit 36 of this example includes a Fourier transform unit 40, a channel matrix calculation unit 42, a weight coefficient multiplication unit 44 and a Fourier inverse transform unit 46. The function of each component will be described later.
　図３は、ＦＴＮ送信の概念を説明する図である。なお、通信システム１００の周波数帯域幅をＷとする。当該周波数帯域幅Ｗは、例えば送信装置１０における送信フィルタ１６の周波数帯域幅で定まる。ＦＴＮ送信ではなく、ナイキストレートで送信データを送信すると、各シンボルの時間間隔はＴ０＝１／（２Ｗ）となる。なお、シンボルの時間間隔とは、例えば隣接するシンボルの中央どうしの間隔である。図３においては、各シンボルを一つの山型の波形で示している。この場合、それぞれのシンボル間においては干渉が生じない。これに対し、ＦＴＮ送信においては、各シンボルの時間間隔はＴ＜Ｔ０となる。このため、各シンボル間において干渉が生じてしまう。 FIG. 3 is a diagram for explaining the concept of FTN transmission. Note that the frequency bandwidth of the communication system 100 is W. The frequency bandwidth W is determined by, for example, the frequency bandwidth of the transmission filter 16 in the transmission device 10. When transmission data is transmitted by Nyquist rate instead of FTN transmission, the time interval of each symbol is T 0 = 1 / (2 W). The symbol time interval is, for example, the interval between the centers of adjacent symbols. In FIG. 3, each symbol is shown by one mountain-shaped waveform. In this case, no interference occurs between the symbols. On the other hand, in FTN transmission, the time interval of each symbol is T <T 0 . For this reason, interference occurs between the symbols.
　通信システム１００は、上記のシンボル間干渉の影響を容易に除去する通信方式を提供する。具体的には、送信装置１０が、送信データの各ブロックの先頭にサイクリックプレフィックス（本明細書では、単にプレフィックスと称する）を付加してからＦＴＮ送信を行う。 The communication system 100 provides a communication method that easily removes the influence of the inter-symbol interference. Specifically, the transmission apparatus 10 performs FTN transmission after adding a cyclic prefix (simply referred to as a prefix in this specification) to the head of each block of transmission data.
　受信装置３０は、受信データの各ブロックにおいてシンボル間干渉が生じる区間を、プレフィックスの長さより短いと仮定して、シンボル間干渉の近似モデルを算出する。つまり、受信データの各ブロックにおいて、プレフィックスの長さより長い区間で生じるシンボル間干渉を無視して、プレフィックスの長さ以下の区間で生じるシンボル間干渉の近似モデルを算出する。例えば、プレフィックスがν個のシンボルを含む場合、ブロックに含まれる各シンボルは、最大でν－１個離れたシンボルに対して干渉を与えると仮定する。当該近似モデルは、少なくとも送信装置１０が各シンボルを送信する時間間隔に基づいて生成する。上記の仮定により、近似モデルは巡回行列で表されるので、当該近似モデルを用いた簡単な演算により、シンボル間干渉の影響を容易に除去することができる。 Receiving device 30 calculates an approximate model of intersymbol interference on the assumption that the section where intersymbol interference occurs in each block of received data is shorter than the prefix length. That is, in each block of received data, an approximate model of intersymbol interference occurring in a section shorter than the prefix length is calculated by ignoring intersymbol interference occurring in a section longer than the prefix length. For example, when the prefix includes ν symbols, it is assumed that each symbol included in the block interferes with a symbol separated by ν−1 at the maximum. The approximate model is generated based on at least a time interval at which the transmitter 10 transmits each symbol. Based on the above assumption, the approximate model is represented by a cyclic matrix, and therefore, the influence of intersymbol interference can be easily removed by a simple calculation using the approximate model.
　図４は、送信装置１０の動作を説明する図である。変調部１２は、ソースビット列を受け取り、予め定められる変調サイズＭおよびブロックサイズＮに基づいて、複数の送信ブロックを生成する。なお変調サイズとは、一つの複素シンボルが取り得る値の数を指す。また、ブロックサイズとは、一つの送信ブロックに含まれる複素シンボルの数を指す。図４では、変調サイズが４のＱＰＳＫ方式を用い、ブロックサイズがＮの場合を示している。本明細書においては、複素シンボルを単にシンボルと略称する。 FIG. 4 is a diagram for explaining the operation of the transmission apparatus 10. The modulation unit 12 receives the source bit string and generates a plurality of transmission blocks based on a predetermined modulation size M and block size N. The modulation size refers to the number of values that a single complex symbol can take. The block size indicates the number of complex symbols included in one transmission block. FIG. 4 shows a case where the QPSK scheme with a modulation size of 4 is used and the block size is N. In this specification, complex symbols are simply abbreviated as symbols.
　変調部１２は、ソースビット列におけるｌｏｇ２Ｍビット毎に一つのシンボルを生成する。そして、複素シンボル列におけるＮシンボル毎に一つの送信ブロックを生成する。つまり、変調部１２は、ソースビット列におけるＮｌｏｇ２Ｍビット毎に送信ブロックを生成する。 The modulation unit 12 generates one symbol for every log 2 M bits in the source bit string. Then, one transmission block is generated for every N symbols in the complex symbol sequence. That is, the modulation unit 12 generates a transmission block for each Nlog 2 M bits in the source bit string.
　プレフィックス付加部１４は、変調部１２が生成した各送信ブロックの先頭に、各ブロックの最後尾における予め定められた長さのデータをコピーしたプレフィックスを付加する。本例では、送信ブロックのシンボル列ｓをｓ０ｓ１・・・ｓＮ－１とし、プレフィックスの長さ（シンボル数）をνとする。プレフィックス付加部１４は、プレフィックス（ｓＮ－ν～ｓＮ－１）を、送信ブロックの先頭に付加する。 The prefix adding unit 14 adds a prefix obtained by copying data having a predetermined length at the end of each block to the head of each transmission block generated by the modulation unit 12. In this example, the symbol sequence s of the transmission block is s 0 s 1 ... S N−1 , and the prefix length (number of symbols) is ν. The prefix adding unit 14 adds the prefix (s N−ν to s N−1 ) to the head of the transmission block.
　送信フィルタ１６は、プレフィックス付加部１４がプレフィックスを付加した後の送信ブロックの帯域を、予め定められた帯域幅Ｗに制限する。送信フィルタ１６は、例えばレイズド・コサインフィルタである。一例として、送信フィルタ１６のロールオフ係数をβ＝０．２２とする。 The transmission filter 16 limits the bandwidth of the transmission block after the prefix adding unit 14 adds the prefix to a predetermined bandwidth W. The transmission filter 16 is, for example, a raised cosine filter. As an example, the roll-off coefficient of the transmission filter 16 is β = 0.22.
　送信部１８は、送信フィルタ１６が帯域制限した各送信ブロックをＦＴＮ送信する。送信部１８が送信するシンボル間隔をＴ＝α・Ｔ０とすると、送信レートＲは下式で表される。但し、αは０から１の間の実数であり、αが小さいほどシンボル間隔が短い。本明細書においては、αをパック係数と称する。
Figure JPOXMLDOC01-appb-M000001
 The transmission unit 18 performs FTN transmission of each transmission block whose band is limited by the transmission filter 16. If the symbol interval transmitted by the transmitter 18 is T = α · T 0 , the transmission rate R is expressed by the following equation. However, α is a real number between 0 and 1, and the symbol interval is shorter as α is smaller. In this specification, α is referred to as a pack coefficient.
Figure JPOXMLDOC01-appb-M000001
　図５は、受信装置３０の動作を説明する図である。受信部３２は、送信部１８が送信した各送信ブロックを受信する。受信部３２が受信する各受信ブロックには、プレフィックスが含まれている。 FIG. 5 is a diagram for explaining the operation of the receiving device 30. The reception unit 32 receives each transmission block transmitted by the transmission unit 18. Each reception block received by the reception unit 32 includes a prefix.
　プレフィックス除去部３４は、各受信ブロックにおけるプレフィックスを除去する。本例では、送信装置１０および受信装置３０の間でタイミング同期がとれていると仮定して、各受信ブロックの先頭からνシンボル分除去している。 The prefix removing unit 34 removes the prefix in each received block. In this example, assuming that timing synchronization is established between the transmission device 10 and the reception device 30, ν symbols are removed from the head of each reception block.
　なお、受信信号は下式で表すことができる。
Figure JPOXMLDOC01-appb-M000002
 　但し、ｎはシンボルの番号、Ｅｓは送信信号に含まれるシンボルの平均パワー、ｈ（ｔ）は送信フィルタ１６のフィルタ特性、ｓｎは送信ブロックの各シンボル、ｎ（ｔ）はチャネル２０におけるランダム雑音を指す。本例においてｎ（ｔ）は、平均値０、分散（ノイズ電力）Ｎ０の複素数のガウス分布雑音である。通信システムにおける信号対雑音比（ＳＮＲ）は、Ｅｓ／Ｎ０で定義される。 The received signal can be expressed by the following equation.
Figure JPOXMLDOC01-appb-M000002
 Here, n is the symbol number, E s is the average power of the symbols included in the transmission signal, h (t) is the filter characteristics of the transmitting filter 16, s n is the symbol of the transmission block, n (t) is the channel 20 Refers to random noise. In this example, n (t) is a complex Gaussian distribution noise having an average value of 0 and a variance (noise power) of N 0 . The signal to noise ratio (SNR) in a communication system is defined as Es / N 0 .
　式（２）から、受信ブロックにおけるｋ番目のシンボルは、下式で表される。
Figure JPOXMLDOC01-appb-M000003
 　式（３）の第１項は送信されたシンボル値を示し、第２項はブロック内におけるシンボル間干渉を示し、第３項はノイズ成分を示す。なお、シンボル間干渉が生じる範囲をνと仮定しているので、長さνのプレフィックスを隔てたブロック間におけるシンボル間干渉は無視する。また、シンボル間干渉の項は、α＝１（Ｔ＝Ｔ０）のときに０となる。ＦＴＮ送信においてはα＜１なので、シンボル間干渉が生じる。干渉除去部３６は、ＦＴＮ送信により生じたシンボル間干渉の影響を除去する。復調部３８は、シンボル間干渉の影響が除去された受信ブロックを復調する。 From equation (2), the k-th symbol in the received block is expressed by the following equation.
Figure JPOXMLDOC01-appb-M000003
 The first term of Equation (3) indicates the transmitted symbol value, the second term indicates intersymbol interference in the block, and the third term indicates a noise component. Since the range where intersymbol interference occurs is assumed to be ν, intersymbol interference between blocks separated by a length ν prefix is ignored. Further, the term of intersymbol interference is 0 when α = 1 (T = T 0 ). In FTN transmission, since α <1, interference between symbols occurs. The interference removal unit 36 removes the influence of intersymbol interference caused by FTN transmission. The demodulator 38 demodulates the received block from which the influence of intersymbol interference has been removed.
　なお、チャネルにおける周波数選択性フェージングおよびディレイスプレッドを考慮すると、受信ブロックにおけるｋ番目のシンボルは、下式で表される。
Figure JPOXMLDOC01-appb-M000004
 　ここで、Ｌはチャネルにおけるディレイスプレッドを、シンボル間隔を単位として示している。また、ｑｌは、ｋ番目のシンボルに対するｌ個前のシンボルの干渉の大きさを示す。 In consideration of frequency selective fading and delay spread in the channel, the kth symbol in the received block is expressed by the following equation.
Figure JPOXMLDOC01-appb-M000004
 Here, L indicates the delay spread in the channel in units of symbol intervals. Further, ql indicates the magnitude of interference of the l-th previous symbol with respect to the k-th symbol.
　時間領域の受信ブロックは、下式で近似される。
Figure JPOXMLDOC01-appb-M000005
 　但し、Ｈは式（５）で定義されるＮ×Ｎの等価チャネルマトリクスであり、受信ブロックにおけるシンボル間干渉を示す。また、ｓはｓ＝[ｓ０,・・・、ｓＮ－１]Ｔで定義されるベクトルであり、ｎはノイズ成分を示す。
Figure JPOXMLDOC01-appb-M000006
 　但し、ｈｋは、等価チャネルマトリクスＨの第ｋ番目の列成分を示す。
　上述したように、シンボル間干渉が生じる範囲をνと仮定することで、等価チャネルマトリクスＨは巡回行列となる。 The reception block in the time domain is approximated by the following equation.
Figure JPOXMLDOC01-appb-M000005
 Here, H is an N × N equivalent channel matrix defined by Equation (5), and indicates intersymbol interference in the received block. Further, s is a vector defined by s = [s 0 ,..., S N−1 ] T , and n indicates a noise component.
Figure JPOXMLDOC01-appb-M000006
 Here, h k represents the k-th column component of the equivalent channel matrix H.
As described above, the equivalent channel matrix H becomes a circulant matrix by assuming that the range in which intersymbol interference occurs is ν.
　図６は、等価チャネルマトリクスＨの概要を示す図である。図６の横方向が等価チャネルマトリクスＨの行方向に対応し、縦方向が列方向に対応する。式（５）に示すように、等価チャネルマトリクスＨは、ｈ（x）（但し、ｘ＝０、１、・・・、νー１）で示される非ゼロのフィルタ係数が巡回して現れる巡回行列で近似される。シンボル間干渉が生じる範囲をνとしたので、各行に含まれるフィルタ係数ｈ（ｘ）の個数はνとなる。本例においてそれぞれのフィルタ係数ｈ(ｘ)は、送信フィルタ１６におけるフィルタ係数で与えられる。 FIG. 6 is a diagram showing an outline of the equivalent channel matrix H. The horizontal direction in FIG. 6 corresponds to the row direction of the equivalent channel matrix H, and the vertical direction corresponds to the column direction. As shown in the equation (5), the equivalent channel matrix H is a cycle in which non-zero filter coefficients represented by h (x) (x = 0, 1,..., Ν−1) appear in a cycle. It is approximated by a matrix. Since the range in which intersymbol interference occurs is ν, the number of filter coefficients h (x) included in each row is ν. In this example, each filter coefficient h (x) is given by a filter coefficient in the transmission filter 16.
　なお、シンボル間干渉が生じる範囲として仮定する区間は、プレフィックスの長さνと同一でなくともよい。例えば、プレフィックスの長さνより短い区間を、シンボル干渉が生じる範囲として仮定してもよい。この場合、等価チャネルマトリクスＨの各行に含まれるｈ（ｘ）の個数は、νより少なくなる。 Note that the interval assumed as the range in which intersymbol interference occurs does not have to be the same as the prefix length ν. For example, a section shorter than the prefix length ν may be assumed as a range in which symbol interference occurs. In this case, the number of h (x) included in each row of the equivalent channel matrix H is less than ν.
　図２に示したチャネルマトリクス算出部４２は、送信部１８におけるシンボル間隔および送信フィルタ１６のフィルタ特性に基づいて、等価チャネルマトリクスＨを算出する。本例のチャネルマトリクス算出部４２は、送信部１８が各シンボルを出力する時間間隔Ｔ、および、送信フィルタ１６のフィルタ係数ｈ（ｘ）に基づいて、等価チャネルマトリクスＨを算出する。これらの情報は、チャネルマトリクス算出部４２に予め記憶されていてよく、また、送信装置１０がチャネルマトリクス算出部４２に送信してもよい。当該情報の送信は、送信データの送信に先立って行ってよく、送信データと同時に行ってもよい。 2 calculates the equivalent channel matrix H based on the symbol interval in the transmission unit 18 and the filter characteristics of the transmission filter 16. The channel matrix calculation unit 42 shown in FIG. The channel matrix calculation unit 42 of this example calculates an equivalent channel matrix H based on the time interval T at which the transmission unit 18 outputs each symbol and the filter coefficient h (x) of the transmission filter 16. These pieces of information may be stored in advance in the channel matrix calculation unit 42, or may be transmitted from the transmission device 10 to the channel matrix calculation unit 42. The transmission of the information may be performed prior to transmission of transmission data or may be performed simultaneously with the transmission data.
　干渉除去部３６は、等価チャネルマトリクスＨで特定されるシンボル間干渉の影響を、受信ブロックから除去する。本例の干渉除去部３６は、受信ブロックを周波数領域の信号に変換して、周波数領域での演算によりシンボル間干渉の影響を除去する。フーリエ変換部４０は、プレフィックスが除去された受信ブロックを高速フーリエ変換して、周波数領域の信号に変換する。なお、本例のフーリエ変換部４０におけるＦＦＴサイズは、ブロック長Ｎと同一とする。ＦＦＴサイズとは、スペクトルの周波数ビンの数を指す。周波数領域の信号に変換してシンボル間干渉の影響を除去することで、干渉除去部３６における演算量を低減することができる。例えば、非特許文献３および４では、時間領域において等化演算を行っているが、シンボル間干渉（チャネルタップ長）の増加とともに演算量が等比級数的に増加してしまう。このため、ＦＴＮを用いた高速通信環境ではリアルタイムに復調することが困難になる。 The interference removal unit 36 removes the influence of intersymbol interference specified by the equivalent channel matrix H from the reception block. The interference removal unit 36 of this example converts the received block into a frequency domain signal, and removes the influence of intersymbol interference by calculation in the frequency domain. The Fourier transform unit 40 performs fast Fourier transform on the received block from which the prefix has been removed, and transforms the received block into a frequency domain signal. The FFT size in the Fourier transform unit 40 of this example is the same as the block length N. The FFT size refers to the number of frequency bins in the spectrum. By converting the signal into a frequency domain signal and removing the influence of intersymbol interference, the amount of calculation in the interference removing unit 36 can be reduced. For example, in Non-Patent Documents 3 and 4, equalization is performed in the time domain, but the amount of calculation increases geometrically as intersymbol interference (channel tap length) increases. For this reason, it is difficult to demodulate in real time in a high-speed communication environment using FTN.
　ウェイト係数乗算部４４は、受信ブロックの各周波数成分に、等価チャネルマトリクスＨに応じたウェイト係数を乗算してシンボル間干渉を除去する。ウェイト係数の算出方法を、以下の式（６）から式（１１）を用いて説明する。 The weight coefficient multiplication unit 44 multiplies each frequency component of the reception block by a weight coefficient corresponding to the equivalent channel matrix H to remove intersymbol interference. A method of calculating the weight coefficient will be described using the following formulas (6) to (11).
　等価チャネルマトリクスＨは巡回行列なので、固有値分解により以下の式で表される。
Figure JPOXMLDOC01-appb-M000007
 　但し、Ｑは離散フーリエ変換行列、Λはｉ番目の要素が等価チャネルマトリクスＨの固有値λ（ｉ，ｉ）で示される対角行列である。ＱＨはＱの共役転置行列であり、離散フーリエ逆変換の演算に対応する。 Since the equivalent channel matrix H is a cyclic matrix, it is expressed by the following equation by eigenvalue decomposition.
Figure JPOXMLDOC01-appb-M000007
 Where Q is a discrete Fourier transform matrix, and Λ is a diagonal matrix in which the i-th element is represented by the eigenvalue λ (i, i) of the equivalent channel matrix H. Q H is a conjugate transpose matrix of Q and corresponds to the inverse Fourier transform operation.
　なお、行列Ｑの第ｌ行、第ｋ列の要素は、下式で示される。
Figure JPOXMLDOC01-appb-M000008
 　また、固有値λは、下式で示される。
Figure JPOXMLDOC01-appb-M000009
 Note that the elements in the l-th row and the k-th column of the matrix Q are expressed by the following equations.
Figure JPOXMLDOC01-appb-M000008
 The eigenvalue λ is expressed by the following equation.
Figure JPOXMLDOC01-appb-M000009
　周波数領域に変換した受信ブロックｙｆは、式（６）に示したＱ、Λを用いて下式で表される。
Figure JPOXMLDOC01-appb-M000010
 　但し、ｓｆは周波数領域に変換した送信ブロック、ｎｆは周波数領域に変換したノイズ成分を示す。 The reception block y f converted to the frequency domain is expressed by the following equation using Q and Λ shown in equation (6).
Figure JPOXMLDOC01-appb-M000010
 Here, s f represents a transmission block converted into the frequency domain, and n f represents a noise component converted into the frequency domain.
　ウェイト係数乗算部４４は、上記の受信ブロックｙｆから、時間領域の送信ブロックｓ＾を復元する。時間領域の送信ブロックｓ＾は、下式で表される。
Figure JPOXMLDOC01-appb-M000011
 　ウェイト係数乗算部４４は、等価チャネルマトリクスＨに基づいて、式（１０）の関係を満たすような対角行列Ｗを算出して、受信ブロックｙｆに乗算する。対角行列Ｗの各要素ω（ｉ，ｉ）は、受信ブロックｙｆの各周波数成分に乗算されるウェイト係数の一例である。式（１０）から明らかなように、ノイズ成分ｎｆが零であれば、対角行列Ｗは対角行列Λの逆行列となる。ノイズ成分ｓｆが零でない場合、対角行列Ｗの各要素は、下式のように最小二乗誤差法（ＭＭＳＥ法）により算出される。
Figure JPOXMLDOC01-appb-M000012
 　但し、λ＊は、λの複素共役を示す。 Weight coefficient multiplication unit 44, from the reception blocks y f, to recover the transmitted block s ^ the time domain. The transmission block s ^ in the time domain is expressed by the following equation.
Figure JPOXMLDOC01-appb-M000011
 Weight coefficient multiplication unit 44, based on the equivalent channel matrix H, and calculate the diagonal matrix W satisfying the relation of equation (10), multiplying the received block y f. Each element of the diagonal matrix W ω (i, i) is an example of the weight coefficients to be multiplied to each frequency component of the received block y f. As is clear from Equation (10), if the noise component n f is zero, the diagonal matrix W is an inverse matrix of the diagonal matrix Λ. When the noise component s f is not zero, each element of the diagonal matrix W is calculated by the least square error method (MMSE method) as shown in the following equation.
Figure JPOXMLDOC01-appb-M000012
 However, λ * indicates a complex conjugate of λ.
　ウェイト係数乗算部４４は、算出した対角行列Ｗを、受信ブロックｙｆに乗算する。フーリエ逆変換部４６は、ウェイト係数が乗算された周波数領域の受信ブロックＷｙｆを、時間領域の信号に逆変換する。フーリエ逆変換部４６における処理は、式（１０）におけるＱＨを乗算する処理に対応する。 Weight coefficient multiplication unit 44, the calculated diagonal matrix W, to multiply the received block y f. The Fourier inverse transform unit 46 inversely transforms the reception block Wy f in the frequency domain multiplied by the weight coefficient into a time domain signal. Processing in the inverse Fourier transform unit 46 corresponds to the process of multiplying the Q H in the formula (10).
　以上の処理により、ＦＴＮ送信により生じたシンボル間干渉の影響の低減を、受信側において少ない演算量で実現できる。つまり、高速ＦＴＮ通信を、現実的な受信演算量で実現できる。これにより、帯域制限された通信システムにおいて、帯域、送信パワーを増加させることなく、送信レートを大幅に向上させることができる。なお、通信システム１００における送信レートは、式（１）で与えられる。 Through the above processing, the effect of intersymbol interference caused by FTN transmission can be reduced with a small amount of computation on the receiving side. That is, high-speed FTN communication can be realized with a realistic reception calculation amount. Thereby, it is possible to greatly improve the transmission rate without increasing the band and the transmission power in the band-limited communication system. Note that the transmission rate in the communication system 100 is given by Expression (1).
　なお、式（１）におけるＮ／（Ｎ＋ν）は、プレフィックスを付加したことによる送信レートのロスを示す。また、プレフィックスを付加したことにより、送信パワーの面でもロスが生じる。このため、変調部１２は、プレフィックスの長さνに対して十分大きいブロックサイズＮを選択することが好ましい。例えば、ブロックサイズＮを、プレフィックスの長さνの数十から百倍以上にする。具体例として、ブロックサイズをＮ＝４０９６、プレフィックスの長さをν＝１０程度にしてよい。このように、プレフィックス付加部１４は、送信データの各ブロックの長さＮに基づいてプレフィックスの長さνを定めてよい。 Note that N / (N + ν) in equation (1) indicates a transmission rate loss due to the addition of a prefix. In addition, the addition of the prefix causes a loss in terms of transmission power. For this reason, it is preferable that the modulation unit 12 selects a block size N that is sufficiently large with respect to the prefix length ν. For example, the block size N is set to several tens to one hundred times the prefix length ν. As a specific example, the block size may be N = 4096 and the prefix length may be about ν = 10. In this manner, the prefix adding unit 14 may determine the prefix length ν based on the length N of each block of transmission data.
　図７は、送信装置１０の動作例を示す図である。Ｓ２０２において、送信装置１０は、Lビットのソースビット列Bを受け取る。Ｓ２０４において、変調部１２は、ソースビット列Ｂを、Ｎ個のシンボルを含む送信ブロックに分割して変調する。 FIG. 7 is a diagram illustrating an operation example of the transmission device 10. In S202, the transmission apparatus 10 receives the L-bit source bit string B. In S204, the modulation unit 12 divides and modulates the source bit string B into transmission blocks including N symbols.
　Ｓ２０６において、プレフィックス付加部１４は、各送信ブロックにプレフィックスを付加する。Ｓ２０８において、送信フィルタ１６は、各送信ブロックを帯域制限する。Ｓ２１０において、送信部１８は、各送信ブロックをＦＴＮ送信する。 In S206, the prefix adding unit 14 adds a prefix to each transmission block. In S208, the transmission filter 16 limits the band of each transmission block. In S210, the transmission unit 18 performs FTN transmission of each transmission block.
　なお、Ｓ２０６において、プレフィックス付加部１４は、ＦＴＮ送信によって生じるシンボル間干渉の度合いに応じて、プレフィックスの長さνを調整してよい。シンボル間干渉の度合いとは、例えば無視できないシンボル間干渉が生じるシンボル間隔の最大値を指す。 In S206, the prefix adding unit 14 may adjust the prefix length ν in accordance with the degree of inter-symbol interference caused by FTN transmission. The degree of intersymbol interference refers to the maximum value of the symbol interval at which intersymbol interference that cannot be ignored, for example.
　プレフィックス付加部１４は、送信部１８におけるシンボル間隔に基づいて、プレフィックスの長さνを定めてよい。シンボル間隔が短いほど、シンボル間干渉の度合いが大きくなるので、プレフィックス付加部１４は、プレフィックスの長さνを大きくする。 The prefix adding unit 14 may determine the prefix length ν based on the symbol interval in the transmission unit 18. The shorter the symbol interval, the greater the degree of intersymbol interference, so the prefix adding unit 14 increases the prefix length ν.
　また、プレフィックス付加部１４は、送信フィルタ１６のフィルタ特性に基づいて、プレフィックスの長さνを定めてよい。例えば送信フィルタ１６のロールオフ係数に基づいて、プレフィックスの長さνを定める。ロールオフ係数が小さいほど、シンボル間干渉の度合いが大きくなるので、プレフィックス付加部１４は、プレフィックスの長さνを大きくする。 Also, the prefix adding unit 14 may determine the prefix length ν based on the filter characteristics of the transmission filter 16. For example, the prefix length ν is determined based on the roll-off coefficient of the transmission filter 16. Since the degree of intersymbol interference increases as the roll-off coefficient decreases, the prefix adding unit 14 increases the prefix length ν.
　図８は、受信装置３０の動作例を示す図である。Ｓ２１２において、受信部３２は、受信信号を周期Ｔでサンプリングして、受信ブロックを生成する。Ｓ２１４において、プレフィックス除去部３４は、各受信ブロックからプレフィックスを除去する。 FIG. 8 is a diagram illustrating an operation example of the receiving device 30. In S212, the reception unit 32 samples the reception signal at a period T to generate a reception block. In S214, the prefix removal unit 34 removes the prefix from each received block.
　Ｓ２１６において、チャネルマトリクス算出部４２は、送信装置１０におけるシンボル送信間隔Ｔおよびフィルタ係数ｈに基づいて、等価チャネルマトリクスＨを算出する。チャネルマトリクス算出部４２またはウェイト係数乗算部４４は、等価チャネルマトリクスＨを固有値分解して、行列ＱおよびΛを更に算出する。 In S216, the channel matrix calculation unit 42 calculates an equivalent channel matrix H based on the symbol transmission interval T and the filter coefficient h in the transmission apparatus 10. The channel matrix calculation unit 42 or the weight coefficient multiplication unit 44 further performs eigenvalue decomposition on the equivalent channel matrix H to further calculate matrices Q and Λ.
　Ｓ２１８において、フーリエ変換部４０は、受信ブロックを高速フーリエ変換する。Ｓ２２０において、ウェイト係数乗算部４４は、式（１１）を用いて、行列Λの各要素λ（ｉ，ｉ）に基づいてウェイト係数ω（ｉ，ｉ）を算出する。 In S218, the Fourier transform unit 40 performs fast Fourier transform on the received block. In S220, the weight coefficient multiplication unit 44 calculates the weight coefficient ω (i, i) based on each element λ (i, i) of the matrix Λ using Expression (11).
　Ｓ２２２において、ウェイト係数乗算部４４は、周波数領域の受信ブロックに、ウェイト係数を乗算する。これにより、受信ブロックからシンボル間干渉（Λ）が除去される。Ｓ２２４において、フーリエ逆変換部４６は、シンボル間干渉が除去された受信ブロックを、時間領域の信号に逆変換する。これにより、ＦＴＮ送信によるシンボル間干渉の影響を低減した送信ブロックを取得する。復調部３８は、フーリエ逆変換部４６が出力する時間領域の信号を復調する。これにより、ＦＴＮ送信により生じたシンボル間干渉の影響の低減を、受信側において少ない演算量で実現できる。 In S222, the weight coefficient multiplication unit 44 multiplies the frequency domain reception block by the weight coefficient. This removes intersymbol interference (Λ) from the received block. In S224, the Fourier inverse transform unit 46 inversely transforms the reception block from which the intersymbol interference is removed into a time domain signal. Thereby, the transmission block which reduced the influence of the intersymbol interference by FTN transmission is acquired. The demodulator 38 demodulates the time domain signal output from the inverse Fourier transform unit 46. As a result, the influence of intersymbol interference caused by FTN transmission can be reduced with a small amount of computation on the receiving side.
　例えば、受信ブロックの高速フーリエ変換は、Ｎ２回の複素乗算で実現できる。また、式（１１）に示したウェイト係数は、４Ｎ回の実数乗算で算出できる。また、式（１０）の乗算は、２Ｎ回の実数乗算で実現できる。そして、高速フーリエ逆変換は、Ｎ２回の複素乗算で実現できる。１回の複素乗算は、４回の実数乗算に相当するから、干渉除去部３６における１シンボル当たりの演算量は、（８Ｎ２＋６Ｎ）／Ｎ＝（８Ｎ＋６）回の実数乗算になる。つまり、干渉除去部３６における演算量は、ブロックサイズＮに比例しており、ブロックサイズＮが増大しても、演算量は等比級数的には増大しない。このため、ブロックサイズＮが増大しても、ＦＴＮ通信を実現することができる。また、変調サイズＭが増大しても、演算量は増大しない。 For example, the fast Fourier transform of the reception block can be realized by N 2 complex multiplications. In addition, the weight coefficient shown in the equation (11) can be calculated by 4N real number multiplications. Further, the multiplication of equation (10) can be realized by 2N real number multiplications. The fast Fourier inverse transform can be realized by N 2 complex multiplications. Since one complex multiplication corresponds to four real number multiplications, the amount of calculation per symbol in the interference removal unit 36 is (8N 2 + 6N) / N = (8N + 6) number real multiplications. That is, the calculation amount in the interference removing unit 36 is proportional to the block size N, and even if the block size N increases, the calculation amount does not increase geometrically. For this reason, even if the block size N increases, FTN communication can be realized. Further, even if the modulation size M increases, the calculation amount does not increase.
　なお、ウェイト係数乗算部４４は、送信部１８におけるシンボル間隔Ｔに基づいて、受信ブロックに重畳されたランダム雑音の大きさＮ０を補正して、シンボル間干渉を除去してよい。この場合、ウェイト係数乗算部４４は、式（１１）におけるＮ０を補正して、各ウェイト係数ωを算出する。ウェイト係数乗算部４４は、シンボル間干渉の度合いが大きいほど、Ｎ０を大きくする。具体的には、ウェイト係数乗算部４４は、シンボル間隔Ｔが小さいほど、Ｎ０を大きくしてよい。例えば、ウェイト係数乗算部４４は、下式に基づいてＮ０を補正する。
Figure JPOXMLDOC01-appb-M000013
 　但し、||ΔＨ||2は、図１０の縦軸における等価チャネルマトリクスＨの推定誤差を示す。 Note that the weight coefficient multiplication unit 44 may correct the random noise magnitude N 0 superimposed on the reception block based on the symbol interval T in the transmission unit 18 to remove intersymbol interference. In this case, the weight coefficient multiplication unit 44 corrects N 0 in Equation (11) and calculates each weight coefficient ω. The weight coefficient multiplier 44 increases N 0 as the degree of intersymbol interference increases. Specifically, the weight coefficient multiplication unit 44 may increase N 0 as the symbol interval T decreases. For example, the weight coefficient multiplication unit 44 corrects N 0 based on the following equation.
Figure JPOXMLDOC01-appb-M000013
 However, || ΔH || 2 represents an estimation error of the equivalent channel matrix H on the vertical axis of FIG.
　図９から図１２は、通信システム１００の特性を評価したシミュレーション結果を示す。シミュレーションの条件は以下の通りである。
　チャネル　　　　　：ＡＷＧＮ（加法性ホワイトガウスノイズ）
　変調方式　　　　　：ＰＳＫまたはＱＡＭ
　フィルタ　　　　　：レイズド・コサインフィルタ
　ブロック長　　　　：４０９６
　パック係数α　　　：０．１～１．０
　ロールオフ率β　　：０．２２
　プレフィックス長ν：１～１００
　ＦＴＮ復調方式　　：ＦＤＥ－ＭＭＳＥ（周波数領域等価－最小二乗誤差法、式１０）
　また、図９から図１２においては、ナイキストレートで送信し（α＝１．０）、最尤推定法（Ｍａｘｉｍｕｍ－Ｌｉｋｅｌｉｈｏｏｄ　ｅｓｔｉｍａｔｉｏｎ）で復号した場合を、「Ｎｏ　ＩＳＩ、ＭＬ　Ｌｉｍｉｔ」として示している。 9 to 12 show simulation results for evaluating the characteristics of the communication system 100. FIG. The simulation conditions are as follows.
Channel: AWGN (Additive white Gaussian noise)
Modulation method: PSK or QAM
Filter: Raised cosine filter Block length: 4096
Pack coefficient α: 0.1 to 1.0
Roll-off rate β: 0.22
Prefix length ν: 1 to 100
FTN demodulation method: FDE-MMSE (frequency domain equivalent-least square error method, Equation 10)
Further, in FIGS. 9 to 12, the case where transmission is performed by Nyquist rate (α = 1.0) and decoding is performed by the maximum likelihood estimation method (Maximum-Likelihood estimation) is shown as “No ISI, ML Limit”. .
　図９は、信号対雑音比（ＳＮＲ）に対するビットエラーレート（ＢＥＲ）を示す図である。但し、変調方式は、ＰＳＫ（ＢＰＳＫ）とした。また、α＝０．７とし、プレフィックス長を１から２０の間で変化させた。これらの条件においては、式（１）による送信レートＲは、１．４３となる。なお、上述したようにＳＮＲは、Ｅｓ／Ｎ０で定義される。図９に示すように、ν＝１０までは、プレフィックス長νを大きくするとＢＥＲが改善することがわかる。 FIG. 9 is a diagram showing a bit error rate (BER) with respect to a signal-to-noise ratio (SNR). However, the modulation method was PSK (BPSK). In addition, α was set to 0.7, and the prefix length was changed between 1 and 20. Under these conditions, the transmission rate R according to the equation (1) is 1.43. As described above, the SNR is defined by E s / N 0 . As shown in FIG. 9, it can be seen that up to ν = 10, the BER is improved by increasing the prefix length ν.
　図１０は、パック係数αに対する等価チャネルマトリクスＨの推定誤差の大きさを示す図である。上述したように、通信システム１００では、シンボル間干渉がνの範囲内でのみ生じると仮定して等価チャネルマトリクスＨを算出している。図１０では、上記の仮定を置かないで算出したマトリクスに対する誤差を算出している。図１０に示すように、パック係数αが小さくなるに従い、推定誤差は大きくなる。プレフィックス長νは、推定誤差が十分小さくなる程度の大きさを有することが好ましい。 FIG. 10 is a diagram showing the magnitude of the estimation error of the equivalent channel matrix H with respect to the pack coefficient α. As described above, in the communication system 100, the equivalent channel matrix H is calculated on the assumption that intersymbol interference occurs only within the range of ν. In FIG. 10, the error for the matrix calculated without making the above assumption is calculated. As shown in FIG. 10, the estimation error increases as the pack coefficient α decreases. The prefix length ν preferably has such a size that the estimation error is sufficiently small.
　図１１は、パック係数αに対するＳＮＲを示す図である。但し、ＢＥＲ＝１０－５とした。図３から予測されるように、αが低い領域では、小さいνにおけるＳＮＲは悪化する。但し、プレフィックス長νを長くしすぎると、伝送効率が悪化する。従って、プレフィックス長νは、パック係数α（シンボル間隔Ｔ）に応じて適切に選択することが好ましい。例えば、α＝０．１程度の場合、プレフィックス長νは５０程度にすることが好ましい。α＝０．２の場合、プレフィックス長νは２０程度にすることが好ましく、α＝０．３以上の場合、プレフィックス長νは１０以下にすることが好ましい。 FIG. 11 is a diagram showing the SNR with respect to the pack coefficient α. However, BER = 10 −5 . As predicted from FIG. 3, in the region where α is low, the SNR at a small ν deteriorates. However, if the prefix length ν is too long, the transmission efficiency deteriorates. Accordingly, the prefix length ν is preferably selected appropriately according to the pack coefficient α (symbol interval T). For example, when α = about 0.1, the prefix length ν is preferably about 50. When α = 0.2, the prefix length ν is preferably about 20, and when α = 0.3 or more, the prefix length ν is preferably 10 or less.
　図１２は、通信システム１００における送受信方式（ＦＤＥ－ＦＴＮ）と、従来の送受信方式（Ｎｏ　ＩＳＩ、ＭＬ　Ｌｉｍｉｔ）とを比較した結果を示す図である。但し、通信システム１００における送受信方式では、α＝０．５とした。つまり、通信システム１００における送受信方式は、同一の変調方式による従来の送受信方式（α＝１．０）に対して、２倍の送信レートＲとなる。図１２におけるＲは式（１）の送信レートであり、相対値を示す。 FIG. 12 is a diagram illustrating a result of comparison between a transmission / reception method (FDE-FTN) in the communication system 100 and a conventional transmission / reception method (No ISI, ML Limit). However, in the transmission / reception method in the communication system 100, α = 0.5. That is, the transmission / reception method in the communication system 100 has a transmission rate R that is twice that of the conventional transmission / reception method (α = 1.0) based on the same modulation method. R in FIG. 12 is the transmission rate of equation (1), and indicates a relative value.
　図１２に示すように、いずれの送信レートＲにおいても、通信システム１００の送受信方式は、従来の送受信方式よりも低いＢＥＲを示している。特に、送信レートが大きくなるにつれて、その差は顕著になる。つまり、通信システム１００によれば、高い送信レートでの通信を容易に実現することができる。 As shown in FIG. 12, at any transmission rate R, the transmission / reception method of the communication system 100 shows a lower BER than the conventional transmission / reception method. In particular, the difference becomes more significant as the transmission rate increases. That is, according to the communication system 100, communication at a high transmission rate can be easily realized.
　以上説明したように、通信システム１００によれば、高速ＦＴＮ通信を、現実的な受信演算量で実現することができる。従来から、ＦＴＮ通信の概念自体は知られていたが、受信側において煩雑な演算を要し、現実的な受信装置の規模でＦＴＮ通信を実現することはできていない。本例の通信システム１００によって、初めて現実的な装置規模で高速ＦＴＮ通信が可能となり、送信レートの飛躍的な増大が期待できる。なお通信システム１００は、無線通信システムに限定されない。光ファイバーによる通信、衛星通信等のあらゆる帯域制限された通信システムに適用することができる。 As described above, according to the communication system 100, high-speed FTN communication can be realized with a realistic reception calculation amount. Conventionally, the concept of FTN communication itself has been known, but complicated operations are required on the receiving side, and FTN communication cannot be realized on a realistic receiving device scale. The communication system 100 of this example enables high-speed FTN communication on a realistic device scale for the first time, and a dramatic increase in transmission rate can be expected. Communication system 100 is not limited to a wireless communication system. The present invention can be applied to any band-limited communication system such as optical fiber communication and satellite communication.
　なお、非特許文献５には、サイクリックプレフィックスを用いた信号の等価が開示されている。しかし、非特許文献５は、チャネルでの周波数選択性フェージングによるシンボル間干渉を除去するものであり、ＦＴＮ送信によるシンボル間干渉を除去することは何ら示唆しておらず、当該文献に記載された等価方法を、ＦＴＮ送信に適用する場合に、どのようなパラメータを用いて受信側が等価処理を実行すべきか等、具体的な適用方法も示唆していない。このため、通信システム１００のように、送信レートを向上させることはできない。 Note that Non-Patent Document 5 discloses signal equivalence using a cyclic prefix. However, Non-Patent Document 5 is to remove intersymbol interference due to frequency selective fading in the channel, and does not suggest any removal of intersymbol interference due to FTN transmission. When the equivalent method is applied to FTN transmission, no specific application method is suggested, such as what parameters should be used by the receiving side to execute the equivalent processing. For this reason, the transmission rate cannot be improved as in the communication system 100.
　図１３は、変調部１２およびプレフィックス付加部１４の動作例を示す図である。本例の変調部１２は、送信すべき情報を示すソースビット列を受け取る。変調部１２は、ソースビット列を、予め定められた長さの複数のサブブロックに分割する。ここで長さとは、サブブロックに含まれるビットの数を指す。本例では、ソースビット列を、６ビットの長さのサブブロックに分割している。それぞれのサブブロックの長さは同一である。 FIG. 13 is a diagram illustrating an operation example of the modulation unit 12 and the prefix addition unit 14. The modulation unit 12 of this example receives a source bit string indicating information to be transmitted. The modulation unit 12 divides the source bit string into a plurality of sub-blocks having a predetermined length. Here, the length indicates the number of bits included in the sub-block. In this example, the source bit string is divided into sub-blocks each having a length of 6 bits. Each sub-block has the same length.
　変調部１２は、各サブブロックについて、ソースビット列の一部のビット値をシンボル位置データとして用い、残りのビット値を送信シンボルＳに変換する。本例の変調部１２は、各サブブロックの最初の４ビットを送信シンボルＳに変換し、残りの２ビットをシンボル位置データとして用いる。 The modulation unit 12 uses a part of the bit values of the source bit string as symbol position data and converts the remaining bit values into transmission symbols S for each sub-block. The modulation unit 12 of this example converts the first 4 bits of each sub-block into a transmission symbol S and uses the remaining 2 bits as symbol position data.
　変調部１２は、各サブブロックの送信シンボルＳおよびシンボル位置データに基づいて、ソースビット列をシンボル列に変換する。具体的には、各サブブロックの送信シンボルＳを、各サブブロックのシンボル位置データに対応するシンボル位置に配置したシンボル列を生成する。シンボル列における各サブブロックは、シンボル位置データのビット数に応じたシンボル数を有する。すなわち、シンボル位置データのビット数をｖとすると、各サブブロック長は２＾ｖシンボル区間である。これにより、シンボル位置データの各ビットパターンに対して、それぞれ異なるシンボル位置が割り当てられる。 The modulation unit 12 converts the source bit string into a symbol string based on the transmission symbol S and symbol position data of each sub-block. Specifically, a symbol string is generated in which transmission symbols S of each subblock are arranged at symbol positions corresponding to the symbol position data of each subblock. Each sub-block in the symbol string has the number of symbols corresponding to the number of bits of the symbol position data. That is, if the number of bits of the symbol position data is v, each sub-block length is 2 ^ v symbol intervals. Thereby, a different symbol position is assigned to each bit pattern of the symbol position data.
　本例では、シンボル位置データのビットパターン００、０１、１０、１１に対して、１番目、２番目、３番目、４番目のシンボル位置が割り当てられる。例えば、本例のサブブロック０のシンボル位置データは０１なので、送信シンボルＳ０は、サブブロック０における２番目のシンボルとなる。 In this example, the first, second, third, and fourth symbol positions are assigned to the bit patterns 00, 01, 10, and 11 of the symbol position data. For example, since the symbol position data of sub-block 0 in this example is 01, transmission symbol S 0 is the second symbol in sub-block 0.
　なお、シンボル列における送信シンボルＳ以外のシンボルの値は、予め定められた一定値に設定される。シンボル間干渉を低減するべく、送信シンボルＳ以外のシンボルの値は零であることが好ましい。 Note that the values of symbols other than the transmission symbol S in the symbol string are set to predetermined constant values. In order to reduce intersymbol interference, the values of symbols other than the transmission symbol S are preferably zero.
　変調部１２は、シンボル列を、Ｎ個のシンボル毎に分割して、図４に関連して説明した送信ブロックを生成する。本例の変調部１２は、送信シンボルＳ以外のシンボル（本例では値が０のシンボル）も含めて、Ｎ個のシンボル毎に分割する。図１３では、一例としてＮ＝１２の例を示している。この場合、変調部１２はサブブロック０からサブブロック２までを一つの送信ブロックとする。ただし、送信ブロックの境界は、サブブロックの境界と一致してよく、一致しなくともよい。 The modulation unit 12 divides the symbol sequence into N symbols, and generates the transmission block described with reference to FIG. The modulation unit 12 in this example divides every N symbols, including symbols other than the transmission symbol S (in this example, symbols having a value of 0). FIG. 13 shows an example where N = 12, as an example. In this case, the modulation unit 12 sets sub-block 0 to sub-block 2 as one transmission block. However, the boundary of the transmission block may or may not coincide with the boundary of the sub-block.
　変調部１２は、シンボル列を分割した送信ブロックをプレフィックス付加部１４に入力する。プレフィックス付加部１４は、各送信ブロックの先頭にプレフィックスを付加する。図１３では、一例として、プレフィックスの長さを３シンボルとしている。 The modulation unit 12 inputs a transmission block obtained by dividing the symbol string to the prefix addition unit 14. The prefix adding unit 14 adds a prefix to the head of each transmission block. In FIG. 13, as an example, the length of the prefix is 3 symbols.
　このように、シンボル位置データに応じた位置に送信シンボルＳを配置することで、送信シンボルＳを連続して配置する場合に比べて、送信シンボルＳの平均間隔を広くすることができる。このため、送信シンボル間の干渉を低減することができる。従って、ＦＴＮ送信における送信レートを大きくしても、送信シンボル間の干渉を抑制することができる。なお、シンボル位置データの情報は、受信した送信シンボルＳの位置から復号できる。 In this way, by arranging the transmission symbols S at positions corresponding to the symbol position data, the average interval of the transmission symbols S can be widened as compared with the case where the transmission symbols S are arranged continuously. For this reason, interference between transmission symbols can be reduced. Therefore, even if the transmission rate in FTN transmission is increased, interference between transmission symbols can be suppressed. The symbol position data information can be decoded from the position of the received transmission symbol S.
　受信装置３０における受信部３２、プレフィックス除去部３４および干渉除去部３６の動作は、図１から図１２に関連して説明した例と同様である。なお、本例におけるシンボル間隔Ｔは、送信シンボルＳの間隔ではなく、送信シンボルＳ以外のシンボルを含めた各シンボルの間隔である。例えばシンボル間隔Ｔは、送信シンボルＳと、値が０のシンボルとの間隔を指す。 The operations of the receiving unit 32, the prefix removing unit 34, and the interference removing unit 36 in the receiving device 30 are the same as those described in connection with FIGS. Note that the symbol interval T in this example is not the interval between the transmission symbols S but the interval between symbols including symbols other than the transmission symbols S. For example, the symbol interval T indicates an interval between the transmission symbol S and a symbol having a value of 0.
　受信装置３０における復調部３８は、受信データにおけるシンボル列を、複数のサブブロックに分割する。サブブロックの長さは、送信装置１０から受信装置３０に通知してよい。復調部３８は、各サブブロックにおける送信シンボルＳと、送信シンボルＳの位置とに基づいて、元のソースビット列を復調する。送信シンボルＳの位置と、元のシンボル位置データのビットパターンとの関係は、送信装置１０から受信装置３０に通知してよい。 The demodulator 38 in the receiving device 30 divides the symbol string in the received data into a plurality of sub-blocks. The length of the sub-block may be notified from the transmission device 10 to the reception device 30. The demodulator 38 demodulates the original source bit string based on the transmission symbol S in each sub-block and the position of the transmission symbol S. The relationship between the position of the transmission symbol S and the bit pattern of the original symbol position data may be notified from the transmission device 10 to the reception device 30.
　図１４は、通信システム１００の他の構成例を示す図である。図１４では、送信部１８、チャネル２０および受信部３２を省略して示している。本例において、送信装置１０は、ＲＳＣエンコーダ５０、第１インターリーバ５２、割り当て部５４、複数のＵＲＣエンコーダ５６、複数の第２インターリーバ５８、複数のＦＴＮサブエンコーダ６０および合成部６２を有する。また、受信装置３０は、割り当て部６４、複数のＦＴＮサブデコーダ６６、複数の第３インターリーバ６８、複数のＵＲＣデコーダ７０、合成部７２、第４インターリーバ７４およびＲＳＣデコーダ７６を有する。 FIG. 14 is a diagram illustrating another configuration example of the communication system 100. In FIG. 14, the transmission unit 18, the channel 20, and the reception unit 32 are omitted. In this example, the transmission apparatus 10 includes an RSC encoder 50, a first interleaver 52, an allocation unit 54, a plurality of URC encoders 56, a plurality of second interleavers 58, a plurality of FTN sub-encoders 60, and a combining unit 62. The receiving device 30 also includes an assigning unit 64, a plurality of FTN sub-decoders 66, a plurality of third interleavers 68, a plurality of URC decoders 70, a combining unit 72, a fourth interleaver 74, and an RSC decoder 76.
　ＲＳＣエンコーダ５０は、送信すべき情報を示すソースビット列に誤り訂正符号であるＲＳＣ（Ｒｅｃｕｒｓｉｖｅ　Ｓｙｓｔｅｍａｔｉｃ　Ｃｏｎｖｏｌｕｔｉｏｎａｌ）符号を付加する。ＲＳＣエンコーダ５０がＲＳＣ符号を付加する元の情報のビット数と、ＲＳＣ符号を付加した後の全体のビット数との比を、ＲＳＣエンコーダ５０における符号化率とする。ただし、ここでＲＳＣエンコーダ５０は任意の畳み込み符号エンコーダで代替可能である。 The RSC encoder 50 adds an RSC (Recursive Systemical Convolutional) code, which is an error correction code, to a source bit string indicating information to be transmitted. The ratio between the number of bits of the original information to which the RSC encoder 50 adds the RSC code and the total number of bits after the RSC code is added is defined as the coding rate in the RSC encoder 50. However, the RSC encoder 50 can be replaced with an arbitrary convolutional code encoder.
　第１インターリーバ５２は、ＲＳＣエンコーダ５０が出力するビット列をインターリーブする。ここで、インターリーブとは、ビットの順番を並べ替える処理を指す。割り当て部５４は、第１インターリーバ５２が出力するＲＳＣ符号が付加されたソースビット列の各ビットを、複数のＵＲＣエンコーダ５６のいずれかに割り当てて入力する。割り当て部５４は、それぞれのＵＲＣエンコーダ５６に入力されるビットの個数の比が、所定の割合となるように、それぞれのビットをいずれかのＵＲＣエンコーダ５６に入力する。 The first interleaver 52 interleaves the bit string output from the RSC encoder 50. Here, interleaving refers to processing for rearranging the order of bits. The allocation unit 54 allocates and inputs each bit of the source bit string to which the RSC code output from the first interleaver 52 is added to one of the plurality of URC encoders 56. The allocation unit 54 inputs each bit to one of the URC encoders 56 so that the ratio of the number of bits input to each URC encoder 56 becomes a predetermined ratio.
　複数のＵＲＣエンコーダ５６は、入力されるビット列に対して、誤り訂正符号であるＵＲＣ（Ｕｎｉｔｙ　Ｒａｔｅ　Ｃｏｎｖｏｌｕｔｉｏｎａｌ）符号を付加する。複数の第２インターリーバ５８は、複数のＵＲＣエンコーダ５６に対して一対一に設けられる。それぞれの第２インターリーバ５８は、対応するＵＲＣエンコーダ５６が出力するビット列をインターリーブする。 The plurality of URC encoders 56 add a URC (Unity Rate Convolutional) code, which is an error correction code, to the input bit string. The plurality of second interleavers 58 are provided one-on-one with respect to the plurality of URC encoders 56. Each second interleaver 58 interleaves the bit string output from the corresponding URC encoder 56.
　複数のＦＴＮサブエンコーダ６０は、複数の第２インターリーバ５８に対して一対一に設けられる。それぞれのＦＴＮサブエンコーダ６０は、対応する第２インターリーバ５８から入力されるビット列に応じたシンボル列を生成する。それぞれのＦＴＮサブエンコーダ６０は、図１から図１３に関連して説明した変調部１２、プレフィックス付加部１４および送信フィルタ１６として機能する。ただし、それぞれのＦＴＮサブエンコーダ６０は、異なる特性を有する。 The plurality of FTN sub-encoders 60 are provided one-on-one with respect to the plurality of second interleavers 58. Each FTN sub-encoder 60 generates a symbol string corresponding to the bit string input from the corresponding second interleaver 58. Each FTN sub-encoder 60 functions as the modulation unit 12, the prefix addition unit 14, and the transmission filter 16 described with reference to FIGS. However, each FTN sub-encoder 60 has different characteristics.
　本例では、複数のＦＴＮサブエンコーダ６０は、それぞれ異なる時間間隔Ｔでシンボルを送信するためのシンボル列を生成する２以上のＦＴＮサブエンコーダ６０を含む。この場合、それぞれのＦＴＮサブエンコーダ６０におけるプレフィックス長が異なる。それぞれのＦＴＮサブエンコーダ６０が生成したシンボル列は、送信部１８により、対応する時間間隔Ｔで送信される。 In this example, the plurality of FTN sub-encoders 60 include two or more FTN sub-encoders 60 that generate symbol sequences for transmitting symbols at different time intervals T, respectively. In this case, the prefix length in each FTN sub-encoder 60 is different. The symbol sequence generated by each FTN sub-encoder 60 is transmitted by the transmission unit 18 at a corresponding time interval T.
　また、複数のＦＴＮサブエンコーダ６０は、図１３に関連して説明したサブブロックの長さがそれぞれ異なる２以上のＦＴＮサブエンコーダ６０を含んでもよい。つまり、それぞれのＦＴＮサブエンコーダ６０において、送信シンボルＳの平均間隔が異なる。 Further, the plurality of FTN sub-encoders 60 may include two or more FTN sub-encoders 60 having different sub-block lengths described with reference to FIG. That is, the average interval of the transmission symbol S is different in each FTN sub-encoder 60.
　また、複数のＦＴＮサブエンコーダ６０は、ロールオフ率βがそれぞれ異なる２以上のＦＴＮサブエンコーダ６０を含んでもよい。また、複数のＦＴＮサブエンコーダ６０は、図１から図１２に関連して説明した変調部１２、プレフィックス付加部１４および送信フィルタ１６におけるいずれかのパラメータが異なる２以上のＦＴＮサブエンコーダ６０を含んでよい。また、複数のＦＴＮサブエンコーダ６０は、変調部１２、プレフィックス付加部１４および送信フィルタ１６におけるいずれかのパラメータが可変であってもよい。 Further, the plurality of FTN sub-encoders 60 may include two or more FTN sub-encoders 60 having different roll-off rates β. The plurality of FTN sub-encoders 60 include two or more FTN sub-encoders 60 having different parameters in the modulation unit 12, the prefix addition unit 14, and the transmission filter 16 described with reference to FIGS. Good. Further, in the plurality of FTN sub-encoders 60, any of the parameters in the modulation unit 12, the prefix addition unit 14, and the transmission filter 16 may be variable.
　合成部６２は、複数のＦＴＮサブエンコーダ６０が出力するシンボル列を合成して、送信部１８に伝送する。合成部６２は、複数のＦＴＮサブエンコーダ６０が出力するシンボル列を順番に結合してよい。 The synthesizing unit 62 synthesizes the symbol sequences output from the plurality of FTN sub-encoders 60 and transmits them to the transmitting unit 18. The combining unit 62 may combine the symbol sequences output from the plurality of FTN sub-encoders 60 in order.
　受信装置３０は、送信装置１０が送信した送信データを復号する。本例の受信装置３０は、送信装置１０における各構成要素に対応する構成要素を有しており、送信装置１０における各構成要素の処理の逆変換を行う。逆変換に必要なプレフィックス長等の情報は、送信装置１０から受信装置３０に通知される。また、受信装置３０は、点線で示されるように、外側の構成および内側の構成の間で互いに処理結果を受け渡す。外側の構成および内側の構成は、相手方の処理結果に基づいて更に情報を処理して、処理結果を相手方に伝送する。このような処理の繰り返しにより、受信データの復号の精度が向上する。繰り返し処理は、例えば下記の文献に記載されている。
　Nan Wu and Lajos Hanzo, "Near-Capacity Irregular-Convolutional-Coding-Aided Irregular Precoded Linear Dispersion Codes" IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 6, JULY 2009. The receiving device 30 decodes the transmission data transmitted by the transmitting device 10. The receiving device 30 of this example includes components corresponding to the respective components in the transmitting device 10 and performs inverse conversion of processing of each component in the transmitting device 10. Information such as a prefix length necessary for reverse conversion is notified from the transmission device 10 to the reception device 30. In addition, as indicated by a dotted line, the receiving device 30 passes processing results between the outer configuration and the inner configuration. The outer configuration and the inner configuration further process information based on the processing result of the other party and transmit the processing result to the other party. By repeating such processing, the accuracy of decoding received data is improved. The iterative process is described in the following document, for example.
Nan Wu and Lajos Hanzo, "Near-Capacity Irregular-Convolutional-Coding-Aided Irregular Precoded Linear Dispersion Codes" IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 6, JULY 2009.
　割り当て部６４は、受信部３２から受け取った受信データのシンボル列を、割り当て部５４におけるビット個数の比に応じた割合で、それぞれのＦＴＮサブデコーダ６６に入力する。複数のＦＴＮサブデコーダ６６は、複数のＦＴＮサブエンコーダ６０と一対一に対応する。それぞれのＦＴＮサブデコーダ６６は、対応するＦＴＮサブエンコーダ６０における処理の逆変換を行う。それぞれのＦＴＮサブデコーダ６６は、プレフィックス除去部３４、干渉除去部３６および復調部３８の機能を有する。 The allocation unit 64 inputs the symbol string of the received data received from the reception unit 32 to each FTN sub-decoder 66 at a rate corresponding to the ratio of the number of bits in the allocation unit 54. The plurality of FTN sub-decoders 66 correspond one-to-one with the plurality of FTN sub-encoders 60. Each FTN sub-decoder 66 performs inverse conversion of processing in the corresponding FTN sub-encoder 60. Each FTN sub-decoder 66 has functions of a prefix removal unit 34, an interference removal unit 36, and a demodulation unit 38.
　複数の第３インターリーバ６８は、複数のＦＴＮサブデコーダ６６と一対一に対応する。それぞれの第３インターリーバ６８は、対応するＦＴＮサブデコーダ６６およびＵＲＣデコーダ７０との間で情報を伝送する。ＦＴＮサブデコーダ６６からＵＲＣデコーダ７０に情報を伝送する場合、第３インターリーバ６８は、第２インターリーバ５８と逆の変換を行うデインタリーバとして機能する。ＵＲＣデコーダ７０からＦＴＮサブデコーダ６６に情報を伝送する場合、第２インターリーバ５８はインターリーバとして機能する。 The plurality of third interleavers 68 correspond one-to-one with the plurality of FTN sub-decoders 66. Each third interleaver 68 transmits information to and from the corresponding FTN sub-decoder 66 and URC decoder 70. When transmitting information from the FTN subdecoder 66 to the URC decoder 70, the third interleaver 68 functions as a deinterleaver that performs a reverse conversion to the second interleaver 58. When transmitting information from the URC decoder 70 to the FTN sub-decoder 66, the second interleaver 58 functions as an interleaver.
　複数のＵＲＣデコーダ７０は、複数の第３インターリーバ６８と一対一に対応する。それぞれのＵＲＣデコーダ７０は、ＵＲＣ符号に基づいて、ビット列の誤りを訂正する。合成部７２は、複数のＵＲＣデコーダが出力するビット列を合成する。また、合成部７２は、外側の第４インターリーバ７４から情報を受け取った場合、それぞれの情報を、対応するＵＲＣデコーダ７０に入力する。ＵＲＣデコーダ７０およびＦＴＮサブデコーダ６６は、外側からの情報に基づいて、受信データを再度処理する。また、ＵＲＣデコーダ７０とＦＴＮサブデコーダ６６間であらかじめ決められた回数だけ出力情報を交換し、復号を行うものとする。 The plurality of URC decoders 70 correspond one-to-one with the plurality of third interleavers 68. Each URC decoder 70 corrects an error in the bit string based on the URC code. The synthesizer 72 synthesizes the bit strings output from the plurality of URC decoders. Further, when the combining unit 72 receives information from the outer fourth interleaver 74, the combining unit 72 inputs each information to the corresponding URC decoder 70. The URC decoder 70 and the FTN sub-decoder 66 process the received data again based on information from the outside. Further, output information is exchanged between URC decoder 70 and FTN subdecoder 66 a predetermined number of times, and decoding is performed.
　第４インターリーバ７４は、合成部７２およびＲＳＣデコーダ７６の間で情報を伝送する。第４インターリーバ７４も、第３インターリーバ６８と同様に、デインタリーバおよびインターリーバの両方として機能する。ＲＳＣデコーダ７６は、入力されたビット列に含まれるＲＳＣ符号を用いて、当該ビット列の誤りを訂正する。 The fourth interleaver 74 transmits information between the combining unit 72 and the RSC decoder 76. Similarly to the third interleaver 68, the fourth interleaver 74 functions as both a deinterleaver and an interleaver. The RSC decoder 76 corrects an error in the bit string using the RSC code included in the input bit string.
　割り当て部５４は、受信装置３０における受信データの復号が最適化されるように、それぞれのＵＲＣエンコーダ５６に割り当てるビット数の比を制御する。最適なビット数の比は、ＥＸＩＴ（ＥＸｔｒｉｎｓｉｃ　Ｉｎｆｏｒｍａｔｉｏｎ　Ｔｒａｎｓｆｅｒ）チャートを用いて解析することができる。 The assigning unit 54 controls the ratio of the number of bits assigned to each URC encoder 56 so that the decoding of the received data in the receiving device 30 is optimized. The optimal bit number ratio can be analyzed using an EXIT (EXTrinsic Information Transfer) chart.
　図１５は、図１４に示した受信装置３０におけるＥＸＩＴチャートの一例を示す。図１５における横軸は、受信装置３０の内側の構成（ＦＴＮサブデコーダ６６およびＵＲＣエンコーダ５６）が、受信装置３０の外側の構成から受け取る入力相互情報量ＩＡを示し、縦軸は、受信装置３０の内側の構成が、受信装置３０の外側の構成に出力する出力相互情報量ＩＥを示す。なお、横軸は、受信装置３０の外側の構成（ＲＳＣデコーダ７６）における出力相互情報量ＩＥにも対応しており、縦軸は、外側の構成における入力相互情報量ＩＡにも対応する。なお、相互情報量の値が１の場合、送信データの情報を完全に復号できたことを示し、０の場合、情報を全く復号できていないことを示す。 FIG. 15 shows an example of an EXIT chart in the receiving apparatus 30 shown in FIG. The horizontal axis in FIG. 15 indicates the input mutual information amount IA received from the configuration outside the receiving device 30 by the configuration inside the receiving device 30 (FTN subdecoder 66 and URC encoder 56), and the vertical axis indicates the receiving device 30. The output mutual information IE to be output to the configuration outside the receiving apparatus 30 is shown in the inner configuration of FIG. The horizontal axis also corresponds to the output mutual information amount IE in the configuration outside the receiving apparatus 30 (RSC decoder 76), and the vertical axis also corresponds to the input mutual information amount IA in the outer configuration. A mutual information amount value of 1 indicates that the transmission data information has been completely decoded, and a value of 0 indicates that the information has not been decoded at all.
　図１５において、実線は、受信装置３０の内側の構成における入力相互情報量および出力相互情報量の関係を示す内側ＥＸＩＴ曲線である。また、破線は、受信装置３０の外側の構成における入力相互情報量および出力相互情報量の関係を示す外側ＥＸＩＴ曲線である。また、丸印でプロットされた線は、ＦＴＮサブデコーダ６６およびＵＲＣエンコーダ５６の各組における入力相互情報量および出力相互情報量の関係を示す個別ＥＸＩＴ曲線である。なお、内側ＥＸＩＴ曲線は、それぞれの個別ＥＸＩＴ曲線を、それぞれのＦＴＮサブデコーダ６６に入力されるシンボルの割合（すなわち、割り当て部５４が、ＵＲＣエンコーダ５６およびＦＴＮサブエンコーダ６０に入力するビットの割合）で重みづけ加算した曲線である。 15, the solid line is an inner EXIT curve showing the relationship between the input mutual information amount and the output mutual information amount in the configuration inside the receiving device 30. A broken line is an outer EXIT curve showing the relationship between the input mutual information amount and the output mutual information amount in the configuration outside the receiving apparatus 30. A line plotted with a circle is an individual EXIT curve showing the relationship between the input mutual information amount and the output mutual information amount in each set of the FTN sub-decoder 66 and the URC encoder 56. The inner EXIT curve is a ratio of symbols inputted to the respective FTN sub-decoders 66 (that is, a ratio of bits inputted by the allocation unit 54 to the URC encoder 56 and the FTN sub-encoder 60). It is a curve weighted and added by.
　受信装置３０の内側の構成には受信データが入力されるので、外側の構成からの入力相互情報量ＩＡがゼロでも、出力相互情報量ＩＥは非ゼロ（図１５では０．２程度）となる。受信装置３０の内側の出力相互情報量ＩＥは、受信装置３０の外側の構成の入力相互情報ＩＡとなる。受信装置３０の外側の構成は、当該入力相互情報ＩＡに対応する出力相互情報ＩＥを出力する（図１５では０．１程度）。受信装置３０の外側の構成の出力相互情報量ＩＥは、受信装置３０の内側の構成の入力相互情報ＩＡとなる。受信装置３０の内側の構成は、入力相互情報ＩＡに応じた出力相互情報ＩＥ（図１５では０．２８程度）を出力する。このような処理を繰り返すことで、相互情報量が徐々に増大していく。 Since the received data is input to the inner configuration of the receiving device 30, the output mutual information IE is non-zero (about 0.2 in FIG. 15) even if the input mutual information IA from the outer configuration is zero. . The output mutual information IE inside the receiving device 30 becomes the input mutual information IA having a configuration outside the receiving device 30. The configuration outside the receiving device 30 outputs output mutual information IE corresponding to the input mutual information IA (about 0.1 in FIG. 15). The output mutual information IE of the configuration outside the receiving device 30 becomes the input mutual information IA of the configuration inside the receiving device 30. The internal configuration of the receiving device 30 outputs output mutual information IE (about 0.28 in FIG. 15) corresponding to the input mutual information IA. By repeating such processing, the mutual information amount gradually increases.
　なお、内側ＥＸＩＴ曲線および外側ＥＸＩＴ曲線は、できるだけ近接していることが好ましい。両曲線が乖離している状態は、送信データに対して必要以上の冗長性を与えていることを示す。このため、伝送効率にロスが生じてしまう。また、受信装置３０の内側ＥＸＩＴ曲線の入力相互情報量ＩＡの全範囲に渡って、内側ＥＸＩＴ曲線の出力相互情報量ＩＥの値が、外側ＥＸＩＴ曲線の入力相互情報量ＩＡの値より大きいことが好ましい。これにより、受信装置３０の内側および外側の構成における相互処理を繰り返すことで相互情報量を１にすることができる。なお、外側ＥＸＩＴ曲線は、ＲＳＣエンコーダ５０における符号化率により変化する。 Note that the inner EXIT curve and the outer EXIT curve are preferably as close as possible. A state where the two curves deviate indicates that the transmission data is given more redundancy than necessary. This causes a loss in transmission efficiency. In addition, the value of the output mutual information amount IE of the inner EXIT curve is larger than the value of the input mutual information amount IA of the outer EXIT curve over the entire range of the input mutual information amount IA of the inner EXIT curve of the receiving device 30. preferable. Thereby, the mutual information amount can be set to 1 by repeating the mutual processing in the configuration inside and outside the receiving apparatus 30. The outer EXIT curve changes depending on the coding rate in the RSC encoder 50.
　本例の割り当て部５４は、ＲＳＣエンコーダ５０における符号化率に基づいて、それぞれのＵＲＣエンコーダ５６およびＦＴＮサブエンコーダ６０に入力するビットの個数の比を制御する。これにより、外側ＥＸＩＴ曲線の変化に応じて、個別ＥＸＩＴ曲線の重みを変更することができ、外側ＥＸＩＴ曲線に近似した内側ＥＸＩＴ曲線を生成することができる。割り当て部５４には、符号化率毎の外側ＥＸＩＴ曲線が予め与えられる。また、割り当て部５４には、それぞれの個別ＥＸＩＴ曲線が予め与えられる。 The allocation unit 54 of this example controls the ratio of the number of bits input to each URC encoder 56 and FTN sub-encoder 60 based on the coding rate in the RSC encoder 50. Thereby, the weight of the individual EXIT curve can be changed according to the change of the outer EXIT curve, and the inner EXIT curve approximated to the outer EXIT curve can be generated. The assigning unit 54 is given in advance an outer EXIT curve for each coding rate. Further, each EXIT curve is given to the allocation unit 54 in advance.
　また、割り当て部５４は、外側ＥＸＩＴ曲線と内側ＥＸＩＴ曲線とが、所定の間隔以下となるように、それぞれのＵＲＣエンコーダ５６に入力するビットの個数の比を制御する。ここで間隔とは、ＥＸＩＴチャートの横軸の所定の値における、縦軸方向の間隔であってよい。一例として、横軸が０．２のときの、縦軸方向における外側ＥＸＩＴ曲線と内側ＥＸＩＴ曲線の差が０．０５以下となるように、それぞれのＵＲＣエンコーダ５６に入力するビットの個数の比を制御してよい。また、間隔は、ＥＸＩＴチャートにおいて外側ＥＸＩＴ曲線と内側ＥＸＩＴ曲線で挟まれる領域の面積で与えられてもよい。 Also, the assigning unit 54 controls the ratio of the number of bits input to each URC encoder 56 so that the outer EXIT curve and the inner EXIT curve are equal to or less than a predetermined interval. Here, the interval may be an interval in the vertical axis direction at a predetermined value on the horizontal axis of the EXIT chart. As an example, when the horizontal axis is 0.2, the ratio of the number of bits input to each URC encoder 56 is set so that the difference between the outer EXIT curve and the inner EXIT curve in the vertical axis direction is 0.05 or less. You may control. The interval may be given by the area of a region sandwiched between the outer EXIT curve and the inner EXIT curve in the EXIT chart.
　また、割り当て部５４は、内側ＥＸＩＴ曲線の入力相互情報量ＩＡの全範囲に渡って、内側ＥＸＩＴ曲線の出力相互情報量ＩＥの値が、外側ＥＸＩＴ曲線の入力相互情報量ＩＡの値より大きくなるように、ビットの個数の比を制御することが好ましい。これにより、相互情報量の上限を１にすることができる。 Further, the assigning unit 54 has a value of the output mutual information amount IE of the inner EXIT curve larger than a value of the input mutual information amount IA of the outer EXIT curve over the entire range of the input mutual information amount IA of the inner EXIT curve. Thus, it is preferable to control the ratio of the number of bits. Thereby, the upper limit of the mutual information amount can be set to 1.
　また、個別ＥＸＩＴ曲線は、チャネル２０におけるＳ／Ｎ比によっても変化する。割り当て部５４は、チャネル２０におけるＳ／Ｎ比に更に基づいて、それぞれのＵＲＣエンコーダ５６に入力するビットの個数の比を制御してよい。割り当て部５４には、Ｓ／Ｎ比毎の個別ＥＸＩＴ曲線が予め与えられる。なお、送信装置１０は、伝送すべき信号を送信する前に、Ｓ／Ｎ比を測定するためのパイロット信号を受信装置３０に送信してよい。受信装置３０は、受け取った既知のパイロット信号に基づいて、チャネル２０におけるＳ／Ｎ比を測定する。受信装置３０は、Ｓ／Ｎ比を送信装置１０に通知する。このような構成により、ＦＴＮ送信における各パラメータの組み合わせを最適化して、送信信号を最適化することができる。 Also, the individual EXIT curve changes depending on the S / N ratio in the channel 20. The allocating unit 54 may further control the ratio of the number of bits input to each URC encoder 56 based on the S / N ratio in the channel 20. The allocation unit 54 is given in advance an individual EXIT curve for each S / N ratio. The transmitting apparatus 10 may transmit a pilot signal for measuring the S / N ratio to the receiving apparatus 30 before transmitting a signal to be transmitted. The receiving device 30 measures the S / N ratio in the channel 20 based on the received known pilot signal. The receiving device 30 notifies the transmitting device 10 of the S / N ratio. With such a configuration, it is possible to optimize a transmission signal by optimizing a combination of parameters in FTN transmission.
　図１６は、コンピュータ１９００のハードウェア構成の一例を示す。コンピュータ１９００は、図１から図１５に関連して説明した送信装置１０の少なくとも一部、または、受信装置３０の少なくとも一部として機能する。２台のコンピュータ１９００が、通信システム１００の少なくとも一部として機能してもよい。 FIG. 16 shows an example of the hardware configuration of the computer 1900. The computer 1900 functions as at least a part of the transmission device 10 described with reference to FIGS. 1 to 15 or at least a part of the reception device 30. Two computers 1900 may function as at least a part of the communication system 100.
　コンピュータ１９００は、ホスト・コントローラ２０８２により相互に接続されるＣＰＵ２０００、ＲＡＭ２０２０、グラフィック・コントローラ２０７５、及び表示装置２０８０を有するＣＰＵ周辺部と、入出力コントローラ２０８４によりホスト・コントローラ２０８２に接続される通信インターフェイス２０３０、ハードディスクドライブ２０４０、及びＣＤ－ＲＯＭドライブ２０６０を有する入出力部と、入出力コントローラ２０８４に接続されるＲＯＭ２０１０、フレキシブルディスク・ドライブ２０５０、及び入出力チップ２０７０を有するレガシー入出力部とを備える。 The computer 1900 includes a CPU peripheral unit having a CPU 2000, a RAM 2020, a graphic controller 2075, and a display device 2080 that are connected to each other by a host controller 2082, and a communication interface 2030 that is connected to the host controller 2082 by an input / output controller 2084. An input / output unit having a hard disk drive 2040 and a CD-ROM drive 2060, and a legacy input / output unit having a ROM 2010, a flexible disk drive 2050, and an input / output chip 2070 connected to the input / output controller 2084.
　ホスト・コントローラ２０８２は、ＲＡＭ２０２０と、高い転送レートでＲＡＭ２０２０をアクセスするＣＰＵ２０００及びグラフィック・コントローラ２０７５とを接続する。ＣＰＵ２０００は、ＲＯＭ２０１０及びＲＡＭ２０２０に格納されたプログラムに基づいて動作し、各部の制御を行う。グラフィック・コントローラ２０７５は、ＣＰＵ２０００等がＲＡＭ２０２０内に設けたフレーム・バッファ上に生成する画像データを取得し、表示装置２０８０上に表示させる。これに代えて、グラフィック・コントローラ２０７５は、ＣＰＵ２０００等が生成する画像データを格納するフレーム・バッファを、内部に含んでもよい。 The host controller 2082 connects the RAM 2020 to the CPU 2000 and the graphic controller 2075 that access the RAM 2020 at a high transfer rate. The CPU 2000 operates based on programs stored in the ROM 2010 and the RAM 2020 and controls each unit. The graphic controller 2075 acquires image data generated by the CPU 2000 or the like on a frame buffer provided in the RAM 2020 and displays it on the display device 2080. Instead of this, the graphic controller 2075 may include a frame buffer for storing image data generated by the CPU 2000 or the like.
　入出力コントローラ２０８４は、ホスト・コントローラ２０８２と、比較的高速な入出力装置である通信インターフェイス２０３０、ハードディスクドライブ２０４０、ＣＤ－ＲＯＭドライブ２０６０を接続する。通信インターフェイス２０３０は、ネットワークを介して他の装置と通信する。ハードディスクドライブ２０４０は、コンピュータ１９００内のＣＰＵ２０００が使用するプログラム及びデータを格納する。ＣＤ－ＲＯＭドライブ２０６０は、ＣＤ－ＲＯＭ２０９５からプログラム又はデータを読み取り、ＲＡＭ２０２０を介してハードディスクドライブ２０４０に提供する。 The input / output controller 2084 connects the host controller 2082 to the communication interface 2030, the hard disk drive 2040, and the CD-ROM drive 2060, which are relatively high-speed input / output devices. The communication interface 2030 communicates with other devices via a network. The hard disk drive 2040 stores programs and data used by the CPU 2000 in the computer 1900. The CD-ROM drive 2060 reads a program or data from the CD-ROM 2095 and provides it to the hard disk drive 2040 via the RAM 2020.
　また、入出力コントローラ２０８４には、ＲＯＭ２０１０と、フレキシブルディスク・ドライブ２０５０、及び入出力チップ２０７０の比較的低速な入出力装置とが接続される。ＲＯＭ２０１０は、コンピュータ１９００が起動時に実行するブート・プログラム、及び／又は、コンピュータ１９００のハードウェアに依存するプログラム等を格納する。フレキシブルディスク・ドライブ２０５０は、フレキシブルディスク２０９０からプログラム又はデータを読み取り、ＲＡＭ２０２０を介してハードディスクドライブ２０４０に提供する。入出力チップ２０７０は、フレキシブルディスク・ドライブ２０５０を入出力コントローラ２０８４へと接続すると共に、例えばパラレル・ポート、シリアル・ポート、キーボード・ポート、マウス・ポート等を介して各種の入出力装置を入出力コントローラ２０８４へと接続する。 Also, the ROM 2010, the flexible disk drive 2050, and the relatively low-speed input / output device of the input / output chip 2070 are connected to the input / output controller 2084. The ROM 2010 stores a boot program that the computer 1900 executes at startup and / or a program that depends on the hardware of the computer 1900. The flexible disk drive 2050 reads a program or data from the flexible disk 2090 and provides it to the hard disk drive 2040 via the RAM 2020. The input / output chip 2070 connects the flexible disk drive 2050 to the input / output controller 2084 and inputs / outputs various input / output devices via, for example, a parallel port, a serial port, a keyboard port, a mouse port, and the like. Connect to controller 2084.
　ＲＡＭ２０２０を介してハードディスクドライブ２０４０に提供されるプログラムは、フレキシブルディスク２０９０、ＣＤ－ＲＯＭ２０９５、又はＩＣカード等の記録媒体に格納されて利用者によって提供される。プログラムは、記録媒体から読み出され、ＲＡＭ２０２０を介してコンピュータ１９００内のハードディスクドライブ２０４０にインストールされ、ＣＰＵ２０００において実行される。 The program provided to the hard disk drive 2040 via the RAM 2020 is stored in a recording medium such as the flexible disk 2090, the CD-ROM 2095, or an IC card and provided by the user. The program is read from the recording medium, installed in the hard disk drive 2040 in the computer 1900 via the RAM 2020, and executed by the CPU 2000.
　コンピュータ１９００にインストールされ、コンピュータ１９００を送信装置１０または受信装置３０として機能させるプログラムは、ＣＰＵ２０００等に働きかけて、コンピュータ１９００を、送信装置１０または受信装置３０としてそれぞれ機能させる。 A program that is installed in the computer 1900 and causes the computer 1900 to function as the transmission device 10 or the reception device 30 works on the CPU 2000 or the like to cause the computer 1900 to function as the transmission device 10 or the reception device 30, respectively.
　これらのプログラムに記述された情報処理は、コンピュータ１９００に読込まれることにより、ソフトウェアと上述した各種のハードウェア資源とが協働した具体的手段である変調部１２、プレフィックス付加部１４、送信フィルタ１６、送信部１８、受信部３２、プレフィックス除去部３４、干渉除去部３６、および、復調部３８の少なくとも一部として機能する。そして、これらの具体的手段によって、本実施形態におけるコンピュータ１９００の使用目的に応じた情報の演算又は加工を実現することにより、使用目的に応じた特有の送信装置１０または受信装置３０が構築される。 The information processing described in these programs is read by the computer 1900, whereby the modulation unit 12, the prefix addition unit 14, the transmission filter, which are specific means in which the software and the various hardware resources described above cooperate. 16, the transmission unit 18, the reception unit 32, the prefix removal unit 34, the interference removal unit 36, and the demodulation unit 38. Then, the specific transmission device 10 or the reception device 30 corresponding to the purpose of use is constructed by realizing calculation or processing of information according to the purpose of use of the computer 1900 in this embodiment by these specific means. .
　一例として、コンピュータ１９００と外部の装置等との間で通信を行う場合には、ＣＰＵ２０００は、ＲＡＭ２０２０上にロードされた通信プログラムを実行し、通信プログラムに記述された処理内容に基づいて、通信インターフェイス２０３０に対して通信処理を指示する。通信インターフェイス２０３０は、ＣＰＵ２０００の制御を受けて、ＲＡＭ２０２０、ハードディスクドライブ２０４０、フレキシブルディスク２０９０、又はＣＤ－ＲＯＭ２０９５等の記憶装置上に設けた送信バッファ領域等に記憶された送信データを読み出してネットワークへと送信し、もしくは、ネットワークから受信した受信データを記憶装置上に設けた受信バッファ領域等へと書き込む。このように、通信インターフェイス２０３０は、ＤＭＡ（ダイレクト・メモリ・アクセス）方式により記憶装置との間で送受信データを転送してもよく、これに代えて、ＣＰＵ２０００が転送元の記憶装置又は通信インターフェイス２０３０からデータを読み出し、転送先の通信インターフェイス２０３０又は記憶装置へとデータを書き込むことにより送受信データを転送してもよい。 As an example, when communication is performed between the computer 1900 and an external device or the like, the CPU 2000 executes a communication program loaded on the RAM 2020 and executes a communication interface based on the processing content described in the communication program. A communication process is instructed to 2030. Under the control of the CPU 2000, the communication interface 2030 reads transmission data stored in a transmission buffer area or the like provided on a storage device such as the RAM 2020, the hard disk drive 2040, the flexible disk 2090, or the CD-ROM 2095, and sends it to the network. The reception data transmitted or received from the network is written into a reception buffer area or the like provided on the storage device. As described above, the communication interface 2030 may transfer transmission / reception data to / from the storage device by a DMA (direct memory access) method. Instead, the CPU 2000 transfers the storage device or the communication interface 2030 as a transfer source. The transmission / reception data may be transferred by reading the data from the data and writing the data to the communication interface 2030 or the storage device of the transfer destination.
　また、ＣＰＵ２０００は、ハードディスクドライブ２０４０、ＣＤ－ＲＯＭドライブ２０６０（ＣＤ－ＲＯＭ２０９５）、フレキシブルディスク・ドライブ２０５０（フレキシブルディスク２０９０）等の外部記憶装置に格納されたファイルまたはデータベース等の中から、全部または必要な部分をＤＭＡ転送等によりＲＡＭ２０２０へと読み込ませ、ＲＡＭ２０２０上のデータに対して各種の処理を行う。そして、ＣＰＵ２０００は、処理を終えたデータを、ＤＭＡ転送等により外部記憶装置へと書き戻す。このような処理において、ＲＡＭ２０２０は、外部記憶装置の内容を一時的に保持するものとみなせるから、本実施形態においてはＲＡＭ２０２０および外部記憶装置等をメモリ、記憶部、または記憶装置等と総称する。本実施形態における各種のプログラム、データ、テーブル、データベース等の各種の情報は、このような記憶装置上に格納されて、情報処理の対象となる。なお、ＣＰＵ２０００は、ＲＡＭ２０２０の一部をキャッシュメモリに保持し、キャッシュメモリ上で読み書きを行うこともできる。このような形態においても、キャッシュメモリはＲＡＭ２０２０の機能の一部を担うから、本実施形態においては、区別して示す場合を除き、キャッシュメモリもＲＡＭ２０２０、メモリ、及び／又は記憶装置に含まれるものとする。 The CPU 2000 is all or necessary from among files or databases stored in an external storage device such as a hard disk drive 2040, a CD-ROM drive 2060 (CD-ROM 2095), and a flexible disk drive 2050 (flexible disk 2090). This portion is read into the RAM 2020 by DMA transfer or the like, and various processes are performed on the data on the RAM 2020. Then, CPU 2000 writes the processed data back to the external storage device by DMA transfer or the like. In such processing, since the RAM 2020 can be regarded as temporarily holding the contents of the external storage device, in the present embodiment, the RAM 2020 and the external storage device are collectively referred to as a memory, a storage unit, or a storage device. Various types of information such as various programs, data, tables, and databases in the present embodiment are stored on such a storage device and are subjected to information processing. Note that the CPU 2000 can also store a part of the RAM 2020 in the cache memory and perform reading and writing on the cache memory. Even in such a form, the cache memory bears a part of the function of the RAM 2020. Therefore, in the present embodiment, the cache memory is also included in the RAM 2020, the memory, and / or the storage device unless otherwise indicated. To do.
　また、ＣＰＵ２０００は、ＲＡＭ２０２０から読み出したデータに対して、プログラムの命令列により指定された、本実施形態中に記載した各種の演算、情報の加工、条件判断、情報の検索・置換等を含む各種の処理を行い、ＲＡＭ２０２０へと書き戻す。例えば、ＣＰＵ２０００は、条件判断を行う場合においては、本実施形態において示した各種の変数が、他の変数または定数と比較して、大きい、小さい、以上、以下、等しい等の条件を満たすかどうかを判断し、条件が成立した場合（又は不成立であった場合）に、異なる命令列へと分岐し、またはサブルーチンを呼び出す。 In addition, the CPU 2000 performs various operations, such as various operations, information processing, condition determination, information search / replacement, etc., described in the present embodiment, specified for the data read from the RAM 2020 by the instruction sequence of the program. Is written back to the RAM 2020. For example, when performing the condition determination, the CPU 2000 determines whether or not the various variables shown in the present embodiment satisfy the conditions such as large, small, above, below, equal, etc., compared to other variables or constants. When the condition is satisfied (or not satisfied), the program branches to a different instruction sequence or calls a subroutine.
　以上、本発明を実施の形態を用いて説明したが、本発明の技術的範囲は上記実施の形態に記載の範囲には限定されない。上記実施の形態に、多様な変更または改良を加えることが可能であることが当業者に明らかである。その様な変更または改良を加えた形態も本発明の技術的範囲に含まれ得ることが、請求の範囲の記載から明らかである。 As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.
　請求の範囲、明細書、および図面中において示した装置、システム、プログラム、および方法における動作、手順、ステップ、および段階等の各処理の実行順序は、特段「より前に」、「先立って」等と明示しておらず、また、前の処理の出力を後の処理で用いるのでない限り、任意の順序で実現しうることに留意すべきである。請求の範囲、明細書、および図面中の動作フローに関して、便宜上「まず、」、「次に、」等を用いて説明したとしても、この順で実施することが必須であることを意味するものではない。 The execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior”. It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for the sake of convenience, it means that it is essential to carry out in this order. is not.
１０・・・送信装置、１２・・・変調部、１４・・・プレフィックス付加部、１６・・・送信フィルタ、１８・・・送信部、２０・・・チャネル、３０・・・受信装置、３２・・・受信部、３４・・・プレフィックス除去部、３６・・・干渉除去部、３８・・・復調部、４０・・・フーリエ変換部、４２・・・チャネルマトリクス算出部、４４・・・ウェイト係数乗算部、４６・・・フーリエ逆変換部、５０・・・ＲＳＣエンコーダ、５２・・・第１インターリーバ、５４・・・割り当て部、５６・・・ＵＲＣエンコーダ、５８・・・第２インターリーバ、６０・・・ＦＴＮサブエンコーダ、６２・・・合成部、６４・・・割り当て部、６６・・・ＦＴＮサブデコーダ、６８・・・第３インターリーバ、７０・・・ＵＲＣデコーダ、７２・・・合成部、７４・・・第４インターリーバ、７６・・・ＲＳＣデコーダ、１００・・・通信システム、１９００・・・コンピュータ、２０００・・・ＣＰＵ、２０１０・・・ＲＯＭ、２０２０・・・ＲＡＭ、２０３０・・・通信インターフェイス、２０４０・・・ハードディスクドライブ、２０５０・・・フレキシブルディスク・ドライブ、２０６０・・・ＣＤ－ＲＯＭドライブ、２０７０・・・入出力チップ、２０７５・・・グラフィック・コントローラ、２０８０・・・表示装置、２０８２・・・ホスト・コントローラ、２０８４・・・入出力コントローラ、２０９０・・・フレキシブルディスク、２０９５・・・ＣＤ－ＲＯＭ DESCRIPTION OF SYMBOLS 10 ... Transmission apparatus, 12 ... Modulation part, 14 ... Prefix addition part, 16 ... Transmission filter, 18 ... Transmission part, 20 ... Channel, 30 ... Reception apparatus, 32 ... Receiving part 34 ... Prefix removing part 36 ... Interference removing part 38 ... Demodulating part 40 ... Fourier transforming part 42 ... Channel matrix calculating part 44 ... Weight coefficient multiplying unit, 46 ... Fourier inverse transform unit, 50 ... RSC encoder, 52 ... first interleaver, 54 ... allocation unit, 56 ... URC encoder, 58 ... second Interleaver, 60 ... FTN sub-encoder, 62 ... combining unit, 64 ... assigning unit, 66 ... FTN sub-decoder, 68 ... third interleaver, 70 ... URC decoder, 72・ ・Synthesizer, 74 ... 4th interleaver, 76 ... RSC decoder, 100 ... communication system, 1900 ... computer, 2000 ... CPU, 2010 ... ROM, 2020 ... RAM, 2030: Communication interface, 2040 ... Hard disk drive, 2050 ... Flexible disk drive, 2060 ... CD-ROM drive, 2070 ... I / O chip, 2075 ... Graphic controller, 2080 ..Display device, 2082 ... Host controller, 2084 ... Input / output controller, 2090 ... Flexible disk, 2095 ... CD-ROM

Claims (16)

  1. 　送信装置および受信装置を含む、帯域制限された通信システムであって、
    　前記送信装置は、
    　送信データの各ブロックの先頭に、各ブロックの最後尾における予め定められた長さのデータをコピーしたプレフィックスを付加するプレフィックス付加部と、
    　前記プレフィックスが付加された前記送信データの各シンボルを、前記通信システムの帯域に応じたナイキストレートよりも短い時間間隔で送信する送信部と
    　を備え、
    　前記受信装置は、
    　受信データの各ブロックから前記プレフィックスを除去するプレフィックス除去部と、
    　前記プレフィックスが除去された各ブロックにおいて、前記送信部が前記ナイキストレートよりも短い時間間隔でシンボルを送信したことにより生じたシンボル間干渉を除去する干渉除去部と
    　を備える通信システム。     A band-limited communication system including a transmitting device and a receiving device,
    The transmitter is
    A prefix adding unit that adds a prefix obtained by copying data of a predetermined length at the end of each block to the head of each block of transmission data;
    A transmission unit that transmits each symbol of the transmission data to which the prefix is added at a time interval shorter than a Nyquist rate according to a band of the communication system,
    The receiving device is:
    A prefix removing unit that removes the prefix from each block of received data;
    A communication system comprising: an interference removal unit that removes intersymbol interference caused by the transmission unit transmitting symbols at a time interval shorter than the Nyquist rate in each block from which the prefix has been removed.
  2. 　前記干渉除去部は、前記受信データの各ブロックにおいて、前記プレフィックスの長さより長い区間で生じる前記シンボル間干渉を無視して、前記プレフィックスの長さ以下の区間で生じる前記シンボル間干渉を除去する
    　請求項１に記載の通信システム。     The interference removal unit ignores the intersymbol interference that occurs in a section longer than the prefix length in each block of the received data, and removes the intersymbol interference that occurs in a section that is shorter than the prefix length. Item 12. The communication system according to Item 1.
  3. 　前記干渉除去部は、前記送信部における各シンボルの時間間隔に基づいて、前記受信データから前記シンボル間干渉を除去する
    　請求項１または２に記載の通信システム。     The communication system according to claim 1 or 2, wherein the interference removal unit removes the intersymbol interference from the reception data based on a time interval of each symbol in the transmission unit.
  4. 　前記送信装置は、前記プレフィックスが付加された前記送信データの帯域幅を、予め定められた帯域幅に制限して前記送信部に入力する送信フィルタを更に備え、
    　前記干渉除去部は、前記送信フィルタのフィルタ特性に基づいて、前記受信データから前記シンボル間干渉を除去する
    　請求項３に記載の通信システム。     The transmission device further includes a transmission filter that limits a bandwidth of the transmission data to which the prefix is added to a predetermined bandwidth and inputs the bandwidth to the transmission unit,
    The communication system according to claim 3, wherein the interference removal unit removes the intersymbol interference from the reception data based on a filter characteristic of the transmission filter.
  5. 　前記プレフィックス付加部は、前記送信部における前記時間間隔、前記送信フィルタのフィルタ特性および前記送信データの各ブロックの長さの少なくとも一つに基づいて、前記プレフィックスの長さを定める
    　請求項４に記載の通信システム。     5. The prefix adding unit determines the length of the prefix based on at least one of the time interval in the transmitting unit, filter characteristics of the transmission filter, and the length of each block of the transmission data. Communication system.
  6. 　前記干渉除去部は、
    　前記ブロックにおけるシンボル間干渉を示す等価チャネルマトリクスを巡回行列で近似し、
    　前記受信データの各周波数成分に対して、前記巡回行列に応じたウェイト係数を乗算して前記シンボル間干渉を除去する
    　請求項１から５のいずれか一項に記載の通信システム。     The interference removing unit
    Approximating an equivalent channel matrix indicating intersymbol interference in the block with a cyclic matrix,
    The communication system according to any one of claims 1 to 5, wherein each inter-symbol interference is removed by multiplying each frequency component of the received data by a weight coefficient corresponding to the cyclic matrix.
  7. 　前記干渉除去部は、前記送信部における前記時間間隔に基づいて、前記受信データに重畳されたランダム雑音の大きさを補正して、前記シンボル間干渉を除去する
    　請求項１から６のいずれか一項に記載の通信システム。     The interference cancellation unit corrects the magnitude of random noise superimposed on the reception data based on the time interval in the transmission unit, and removes the inter-symbol interference. The communication system according to item.
  8. 　前記送信装置は、
    　送信すべき情報を示すソースビット列を受け取り、ソースビット列を予め定められた長さの複数のサブブロックに分割し、各サブブロックのソースビット列を、ソースビット列の一部のビット値に対応するシンボル位置に、ソースビット列の残りのビット値に応じた送信シンボルを有するシンボル列に変換して、前記プレフィックス付加部に入力する変調部を更に備え、
    　前記プレフィックス付加部は、シンボル列を分割した前記ブロックの先頭に、前記プレフィックスを付加する
    　請求項１から７のいずれか一項に記載の通信システム。     The transmitter is
    A source bit string indicating information to be transmitted is received, the source bit string is divided into a plurality of sub-blocks of a predetermined length, and the source bit string of each sub-block is a symbol position corresponding to a partial bit value of the source bit string Further comprising a modulation unit that converts a symbol string having a transmission symbol corresponding to the remaining bit value of the source bit string and inputs the symbol string to the prefix adding unit,
    The communication system according to any one of claims 1 to 7, wherein the prefix adding unit adds the prefix to a head of the block obtained by dividing a symbol string.
  9. 　前記受信装置は、前記受信データにおける各サブブロックについて、前記送信シンボルと、前記送信シンボルの位置とに基づいて、前記ソースビット列を復調する復調部を更に備える
    　請求項８に記載の通信システム。     The communication system according to claim 8, wherein the reception apparatus further includes a demodulation unit that demodulates the source bit sequence based on the transmission symbol and the position of the transmission symbol for each sub-block in the reception data.
  10. 　前記送信装置は、
    　送信すべき情報を示すソースビット列にＲＳＣ符号を付加するＲＳＣエンコーダと、
    　入力されるビット列に応じたシンボル列を生成する複数の変調部と、
    　前記ＲＳＣエンコーダがＲＳＣ符号を付加した前記ソースビット列の各ビットを、前記複数の変調部のいずれかに割り当てて入力する割り当て部と、
    　前記複数の変調部が生成したシンボル列を合成する合成部と
    　を有し、
    　前記複数の変調部は、それぞれ異なる時間間隔でシンボルを送信するための前記シンボル列を生成する２以上の変調部を含み、
    　前記割り当て部は、前記ＲＳＣエンコーダにおける符号化率に基づいて、それぞれの変調部に入力するビットの個数の比を制御する
    　請求項１から９のいずれか一項に記載の通信システム。     The transmitter is
    An RSC encoder for adding an RSC code to a source bit string indicating information to be transmitted;
    A plurality of modulation units for generating a symbol string corresponding to the input bit string;
    An allocation unit that allocates and inputs each bit of the source bit sequence to which the RSC encoder has added an RSC code to any of the plurality of modulation units;
    A combining unit that combines the symbol sequences generated by the plurality of modulation units,
    The plurality of modulation units include two or more modulation units that generate the symbol sequences for transmitting symbols at different time intervals, respectively.
    The communication system according to any one of claims 1 to 9, wherein the allocation unit controls a ratio of the number of bits input to each modulation unit based on a coding rate in the RSC encoder.
  11. 　前記割り当て部は、
    　前記ＲＳＣエンコーダの符号化率に応じた外側ＥＸＩＴ曲線と、前記複数の変調部に対応する複数の個別ＥＸＩＴ曲線を合成した内側ＥＸＩＴ曲線とが、予め定められた間隔以下となるように、前記ビットの個数の比を制御する
    　請求項１０に記載の通信システム。     The assigning unit is
    The bit is set such that an outer EXIT curve corresponding to a coding rate of the RSC encoder and an inner EXIT curve obtained by combining a plurality of individual EXIT curves corresponding to the plurality of modulation units are equal to or less than a predetermined interval. The communication system according to claim 10, wherein the ratio of the number of the control points is controlled.
  12. 　前記複数の変調部は、入力されたビット列を予め定められた長さの複数のサブブロックに分割し、各サブブロックのビット列を、ビット列の一部のビット値に対応するシンボル位置に、ビット列の残りのビット値に応じた送信シンボルを有するシンボル列に変換する２以上の変調部を含み、
    　前記２以上の変調部におけるサブブロックの長さが異なる
    　請求項１０または１１に記載の通信システム。     The plurality of modulation units divide the input bit string into a plurality of sub-blocks having a predetermined length, and the bit string of each sub-block is placed at a symbol position corresponding to a partial bit value of the bit string. Including two or more modulation units for converting into a symbol string having transmission symbols according to the remaining bit values;
    The communication system according to claim 10 or 11, wherein lengths of sub-blocks in the two or more modulation units are different.
  13. 　帯域制限された通信システムにおける送信装置であって、
    　送信データの各ブロックの先頭に、各ブロックの最後尾における予め定められた長さのデータをコピーしたプレフィックスを付加するプレフィックス付加部と、
    　前記プレフィックスが付加された前記送信データの各シンボルを、前記通信システムの帯域に応じたナイキストレートよりも短い時間間隔で送信する送信部と
    　を備える送信装置。     A transmission device in a bandwidth-limited communication system,
    A prefix adding unit that adds a prefix obtained by copying data of a predetermined length at the end of each block to the head of each block of transmission data;
    A transmission apparatus comprising: a transmission unit that transmits each symbol of the transmission data to which the prefix is added at a time interval shorter than a Nyquist rate according to a band of the communication system.
  14. 　帯域制限された通信システムにおける受信装置であって、
    　受信データの各ブロックからプレフィックスを除去するプレフィックス除去部と、
    　前記プレフィックスが除去された前記各ブロックから、送信装置が前記通信システムのナイキストレートよりも短い時間間隔でシンボルを送信したことにより生じたシンボル間干渉を除去する干渉除去部と
    　を備える受信装置。     A receiving device in a band-limited communication system comprising:
    A prefix removal unit that removes a prefix from each block of received data;
    A receiving apparatus comprising: an interference removing unit that removes inter-symbol interference generated by transmitting a symbol at a time interval shorter than a Nyquist rate of the communication system from each block from which the prefix has been removed.
  15. 　送信装置および受信装置を含む、帯域制限された通信システムにおける通信方法であって、
    　前記送信装置は、
    　送信データの各ブロックの先頭に、各ブロックの最後尾における予め定められた長さのデータをコピーしたプレフィックスを付加し、
    　前記プレフィックスが付加された前記送信データの各シンボルを、前記通信システムの帯域に応じたナイキストレートよりも短い時間間隔で送信し、
    　前記受信装置は、
    　受信データから前記プレフィックスを除去し、
    　前記プレフィックスが除去された前記受信データから、前記送信装置が前記ナイキストレートよりも短い時間間隔でシンボルを送信したことにより生じたシンボル間干渉を除去する
    　通信方法。     A communication method in a band-limited communication system including a transmission device and a reception device,
    The transmitter is
    At the beginning of each block of transmission data, add a prefix that is a copy of data of a predetermined length at the end of each block,
    Each symbol of the transmission data to which the prefix is added is transmitted at a time interval shorter than Nyquist rate according to the bandwidth of the communication system,
    The receiving device is:
    Removing the prefix from the received data;
    A communication method for removing intersymbol interference caused by the transmission apparatus transmitting symbols at a time interval shorter than the Nyquist rate from the received data from which the prefix has been removed.
  16. 　コンピュータを、請求項１３に記載の送信装置、または、請求項１４に記載の受信装置として機能させるプログラム。 A program that causes a computer to function as the transmission device according to claim 13 or the reception device according to claim 14.
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