CN102938745B

CN102938745B - Wireless communications method

Info

Publication number: CN102938745B
Application number: CN201210457892.9A
Authority: CN
Inventors: 下村刚史; 木村大
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 2006-12-22
Filing date: 2006-12-22
Publication date: 2017-08-25
Anticipated expiration: 2026-12-22
Also published as: CN102938745A

Abstract

The present invention provides a kind of wireless communications method, the data of the 1st and the 2nd user are sent using the 1st and the 2nd subcarrier group respectively, it is transmitted for the pilot signal of the data-reusing the 1st and the 2nd user, the wireless communications method is characterised by, the pilot signal for the 1st and the 2nd user for applying cyclic shift to Zadoff Chu sequences respectively and generating is configured at different frequency, the pilot signal of the 1st and the 2nd user is directed to respectively, so that the subcarrier of more than 1 for sending the high frequency band side of frequency band is equal with the frequency component of the subcarrier of more than 1 of low-frequency band side.

Description

Wireless communication method

The present application is a divisional application of an invention patent application having an application date of 22/12/2006 and an application number of 200680056539.2, entitled "wireless communication method, base station, and user terminal".

Technical Field

The present invention relates to a wireless communication method, a base station and a user terminal, and more particularly, to a wireless communication method, a base station and a user terminal in a wireless communication system as follows: each user terminal transmits a data signal to the base station using frequencies of data transmission bands different from each other allocated by the base station, and time-division multiplexes a pilot signal for the data signal and transmits the data signal to the base station.

Background

In a wireless communication system such as a cellular system, a reception side generally performs timing synchronization and transmission path estimation (channel estimation) using a known pilot signal, and demodulates data based on the timing synchronization and the transmission path estimation. In an adaptive modulation scheme in which throughput is improved by adaptively changing a modulation scheme, a coding rate, and the like according to channel quality, a pilot signal is also used when estimating channel quality, for example, signal to interference ratio (sir) or the like, in order to determine an optimal modulation scheme and an optimal coding rate.

As a radio access scheme having high resistance to frequency selective fading due to multipath in wide-band radio communication, there is an OFDM (orthogonal frequency division Multiplexing) scheme. However, OFDM has a problem that the PAPR (Peak to Average power Ratio) of a transmission signal is large, and is not suitable as an uplink transmission scheme from the viewpoint of power efficiency of a terminal. Therefore, in 3GPP LTE, which is a second-generation cellular system, the uplink transmission scheme is a single-carrier transmission scheme in which frequency equalization is performed on the receiving side (non-patent document 1). Single carrier transmission means multiplexing transmission data and pilot signals only on the time axis, and PAPR can be greatly reduced compared to OFDM in which data and pilot signals are multiplexed on the frequency axis.

Single carrier transmission

Fig. 23 shows an example of a frame format of single-carrier transmission, and fig. 24 shows an explanatory diagram of frequency equalization. The frame is formed by time-division multiplexing Data and Pilot, each of which is formed of N samples, and in fig. 23, two Pilot blocks are inserted into 1 frame. In frequency equalization, the Data/Pilot separation section 1 separates Data and Pilot, and the first FFT section 2 performs FFT processing on N sample Data, generates N frequency components, and inputs the frequency components to the channel compensation section 3. The second FFT unit 4 performs FFT processing on the N sample pilots to generate N frequency components, and the channel estimation unit 5 estimates channel characteristics for each frequency using the N frequency components and the N frequency components of the known pilots, and inputs the channel compensation signal to the channel compensation unit 3. The channel compensation unit 3 multiplies the N frequency components output from the first FFT unit 2 by a channel compensation signal for each frequency to perform channel compensation, and the IFFT unit 6 performs IFFT processing on the N frequency components subjected to channel compensation, converts the processed N frequency components into a time signal, and outputs the time signal.

CAZAC sequence

In single-carrier transmission, when frequency equalization is performed on the receiving side, in order to perform channel estimation with high accuracy in the frequency domain, it is desirable that the pilot signal have a constant amplitude in the frequency domain, in other words, it is desirable that the autocorrelation of an arbitrary periodic time shift be 0. On the other hand, from the viewpoint of PAPR, it is desirable that the amplitude is constant also in the time domain. A Constant Amplitude Zero Auto-Correlation (CAZAC) sequence is known as a pilot sequence for realizing these characteristics, and it is specified in 3GPP LTE that the CAZAC sequence is applied as an uplink pilot. CAZAC sequences have ideal autocorrelation, so the amounts obtained by cyclic shifts of the same sequence are orthogonal to each other. In 3GPP LTE, a method of multiplexing pilot signals of different users using CAZAC sequences having different cyclic shift amounts or multiplexing pilot signals of different antennas by the same user is called CDM (Code Division multiple access).

A Zadoff-Chu sequence, which is a representative CAZAC sequence, is represented by formula (1) (non-patent document 2).

ZC_k(n)＝exp{-j2πk/L·(qn+n(n+L％2)/2)} (1)

Wherein k and L are relatively prime and respectively represent sequence number and sequence length. n represents a code number, q represents an arbitrary integer, and L%2 represents a remainder obtained by dividing L by 2, which may be expressed as Lmod (2). When the prime factor of L is expressed by the following formula (2) (gi is a prime number),

the number of natural numbers smaller than L, which are coprime to L, i.e., the number of sequences of the CAZAC sequence, [ phi ] (L), is obtained by the following equation (3).

Specifically, if L is 12, L is 12 is 2²×3¹Therefore, g1 is 2, e1 is 2, g2 is 3, and e2 is 1, and the number of sequences k in the CAZAC sequence is 4 according to formula (3). Therefore, the larger L and the smaller the prime factor, the larger the number of sequences. In other words, if L is a prime number, the number k of sequences of the CAZAC sequence is (L-1).

Making CAZAC sequences ZC_k(n) ZC by Cyclic Shift c_k(n-c) is represented by the following formula (4).

ZC_k(n-c)＝exp{-j2πk/L·(q(n-c)+(n-c)(n-c+L％2)/2)} (4)

As shown in the following formula (5),

ZC_k(n) and ZC_kSince the correlation degree R (τ) of (n-c) is 0 at a point other than τ ═ c, it is assigned to the parent sequence ZC having the same sequence number_k(n) sequences obtained by adding different cyclic shift amounts are orthogonal to each other.

When a plurality of pilots multiplexed by CDM based on cyclic shift are received in a radio base station, the pilots can be delimited from the beginning by acquiring the correlation degree with the mother sequence. As the interval of the cyclic shift is smaller, the multipath and the reception timing offset are less resistant, and therefore the number of possible multiplexes is limited. A cyclic shift amount c allocated to the P-th pilot when the number of multiplexing by cyclic shift is P_pFor example, it can be determined from the following formula (6) (non-patent document 3).

c_p=(p-1)*[L/p]Wherein, P =1,, P (6)

As described above, pilot and data are time-division multiplexed in the uplink of 3GPP LTE and transmitted in the SC-FDMA manner. FIG. 25 is a structural diagram of an SC-FDMA transmitter, and size N is shown in FIG. 7_TXDFT (Discrete fourier transform), 8 'denotes a subcarrier mapping part, and 9' denotes a size N_FFTThe IDFT unit of (2), 10, denotes a CP (cyclic prefix) insertion unit. In 3gpp lte, N is used to suppress the throughput_FFTSet to an integer raised to the power of 2 and replace the IDFT after subcarrier mapping with IFFT.

For mother sequence ZC_k(N) the process of applying the cyclic shift c may be performed before the DFT or after the IFFT when performed after the IFFT, the cyclic shift c × N may be performed_FFT/N_TXAnd (4) sampling. Since the processes are substantially the same, a case where the cyclic shift process is performed before the DFT will be described as an example.

Problems of the prior art

In order to reduce inter-cell interference, CAZAC sequences of different sequence numbers need to be reused as pilots between cells. This is because the larger the number of repetitions is, the larger the distance between cells using the same sequence is, and therefore the possibility of generating severe interference is reduced. For this reason, it is necessary to secure many CAZAC sequences, and the properties of the CAZAC sequences require that the sequence length L be a large prime number. Fig. 26 is an explanatory diagram of interference between cells, and when the number of CAZAC sequences that can be used is 2 as shown in (a), a CAZAC sequence having the same sequence number is used between adjacent cells, and thus serious interference of pilots occurs. As shown in (B), when the number of CAZAC sequences is 3, CAZAC sequences having the same sequence number are not used in adjacent cells, but the number of repetitions is 3 and is relatively small, so that the distance between cells using CAZAC sequences having the same sequence number is relatively short, and the possibility of interference increases. As shown in (C), when the number of CAZAC sequences is 7, the number of repetitions is 7, which is relatively large, so that the inter-cell distance of CAZAC sequences using the same sequence number increases, and the possibility of interference gradually decreases.

However, in 3GPP LTE, as shown in fig. 27 (a), the number of occupied subcarriers of data is set to a multiple of 12, and the subcarrier interval of pilot is set to 2 times the subcarrier interval of data, so as to improve transmission efficiency. In this case, when the sequence length L of the CAZAC sequence is 6, the number of sequences k is 2, and the CAZAC sequences having the same sequence number are used in adjacent cells, so that interference of pilots occurs. When the sequence length L is set to 5, k is 4, but is still relatively small, and as shown in fig. 27 (B), subcarriers of data not covered by pilots are generated, which deteriorates the channel estimation accuracy.

Therefore, in consideration of making the transmission band of the pilot signal wider than the transmission band of the data at the time of transmission, a sufficient sequence length can be secured (3 GPP R1-060925, R1-063183). Fig. 28 shows an example of the case where the number of multiplexed pilot signals is 2. When the sequence length L is 12, the CAZAC sequences can be only 4, and the inter-cell interference increases (k is 4). Therefore, the sequence length L is set to a prime number 11. When L is set to 11, 10 CAZAC sequences (k is 10) can be acquired, and the inter-cell interference can be reduced. The sequence length L cannot be set to 13 or more. This is because interference with an adjacent frequency band occurs when the frequency band is 13 or more.

Pilot signals of different users are multiplexed by CDM based on cyclic shift. Namely, the pair L is 11 CAZAC sequence ZC_k(n) the result of cyclic shift c1 is used as pilot for user 1, and the CAZAC sequence ZC is used_k(n) the result of applying cyclic shift c2 is used as the pilot for user 2.

However, in the case of CAZAC sequence ZC where L is 11_kWhen (n) is cyclically shifted and used for users 1 and 2, as is clear from fig. 28, the relative relationship between the pilot transmission band and the data transmission band differs between user 1 and user 2, and the channel estimation accuracy differs. That is, subcarriers 23 and 24 in the transmission band of the data of user 2 are shifted from the transmission band of the pilot, and the channel estimation accuracy in the subcarriers deteriorates.

In fig. 28, the subcarrier spacing of the pilot is set to 2 times the subcarrier spacing of the data according to the current 3GPP LTE standard, but the above problem occurs even when the ratio of the subcarrier spacing changes.

Non-patent document 1: 3GPP TR25814-700figure9.1.1-1

Non-patent document 2: popovic, "Generalized Chirp-Like polypeptide sequence switching protocols", IEEE trans. info. theory, Vol.38, pp.1406-1409, July 1992.

Non-patent document 3: 3GPP R1-060374, "Text Proposal On Uplink ReferenceSignalStructure", TIInstructions

Disclosure of Invention

In view of the above, an object of the present invention is to enable channel estimation of data subcarriers shifted from a pilot transmission band with high accuracy.

Another object of the present invention is toPairing predetermined sequences (e.g. CAZAC sequences ZC)_k(n)) the result of performing cyclic shifts of different amounts is used as a pilot for the user to be multiplexed, and channel estimation of subcarriers allocated to each user can be performed with high accuracy.

Another object of the present invention is to separate pilots of respective users and perform channel estimation by a simple method even when the result of performing different amounts of cyclic shifts on a predetermined CAZAC sequence is used as pilots of users to be multiplexed.

Another object of the present invention is to improve the channel estimation accuracy of data subcarriers of a user even for the user whose propagation path conditions are not good.

The present invention provides a radio communication method, a base station, and a user terminal in a radio communication system in which each user terminal transmits a data signal to the base station using frequencies of mutually different data transmission bands allocated by the base station, and transmits a pilot signal to the base station by time-division multiplexing the data signal.

Wireless communication method

The wireless communication method of the present invention includes the steps of performing: carrying out frequency offset on a part of frequency bands of a total data transmission frequency band by each user terminal to determine a pilot frequency transmission frequency band of the user terminal so that the pilot frequency transmission frequency band of the user terminal covers the data transmission frequency band of the user terminal; and instructing, for each user terminal, the user terminal to transmit a pilot signal using the determined frequency of the pilot transmission band.

The instructing step includes the step of performing the following processing: calculating the offset of the frequency offset and the cyclic shift corresponding to the multiplexing number of the user terminal aiming at each user terminal; and instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount, and instructing the user terminal to frequency-shift the pilot signal by the frequency offset amount.

The following steps are performed in the base station: adding frequency components of pilot signals which do not overlap with each other when multiplexing and receiving a plurality of pilot signals transmitted from a plurality of user terminals; multiplying the addition result by a replica of the pilot signal; and converting the replica multiplication result into a time domain signal, and then separating a signal portion of a predetermined user terminal from the time domain signal to perform channel estimation.

The wireless communication method of the present invention further includes the step of performing: acquiring the transmission path condition of a mobile station; the intermediate band of the total band is preferentially allocated and notified to the user terminal as a data transmission band of the user terminal having a poor propagation path condition. Alternatively, the radio communication method of the present invention further includes the step of performing: and performing hopping control, and periodically allocating a middle frequency band and an edge frequency band of the total frequency band as data transmission frequency bands of the user terminals.

Base station

The base station of the present invention includes a resource management unit that determines a pilot transmission band of a user terminal by applying frequency offset to a partial band of a total data transmission band for each user terminal, and instructs the user terminal to transmit a pilot signal using the frequency of the determined pilot transmission band while covering the data transmission band of the user terminal with the pilot transmission band of the user terminal.

In the base station, the resource management unit includes: a cyclic shift amount calculation unit that calculates, for each user terminal, an offset amount of the frequency offset and a cyclic shift amount corresponding to the number of multiplexing of the user terminal; and an instruction unit configured to instruct a user terminal to cause the user terminal to rotate the pilot signal of the CAZAC sequence by the cyclic shift amount and to instruct the user terminal to cause the user terminal to frequency-shift the pilot signal by the frequency offset amount.

The base station further includes a channel estimation unit for performing channel estimation for each user terminal, the channel estimation unit including: a reception unit that multiplexes and receives a plurality of pilot signals transmitted from a plurality of user terminals; an adding section that adds frequency components of pilot signal portions in which the plurality of pilot signals do not overlap with each other; a replica multiplication unit for multiplying the addition result by a replica of the pilot signal; a conversion unit that converts the replica multiplication result into a time domain signal; a separation section that separates a signal portion of a predetermined user terminal from the time domain signal; and an estimation unit that converts the separated time signal into a signal in a frequency domain to perform channel estimation.

The resource management unit acquires a propagation path situation of the mobile station, preferentially allocates an intermediate band of the total band, and notifies the user terminal of the intermediate band as a data transmission band of the user terminal having a poor propagation path situation. Alternatively, the resource management unit may perform a hopping control to periodically allocate the middle band and the edge band of the total band as the data transmission band for each user terminal.

User terminal

A user terminal of a wireless communication system comprises: a reception unit that receives uplink resource information from a base station; and a pilot generation unit that generates a pilot in accordance with the instruction of the uplink resource information, the pilot generation unit including: a CAZAC sequence generating section that generates a CAZAC sequence having a predetermined sequence length and a sequence number as a pilot signal based on the resource information; a 1 st conversion unit that converts a CAZAC sequence, which is a pilot signal in the time domain, into a pilot signal in the frequency domain; a subcarrier mapping unit that maps subcarrier components of a pilot signal based on frequency offset information included in the resource information; a 2 nd conversion unit for converting the pilot signal subjected to the subcarrier mapping into a signal in a time domain; and a cyclic shift unit that cyclically shifts the CAZAC sequence according to the amount of shift included in the resource information before the 1 st conversion or after the 2 nd conversion.

Drawings

Fig. 1 is a 1 st principle explanatory diagram of the present invention.

Fig. 2 is a 2 nd schematic explanatory view of the present invention.

Fig. 3 is a 3 rd schematic illustration of the present invention.

FIG. 4 is a block diagram of a method for implementing frequency offset d subcarriers and cyclic shift (c)₂-s (k, d, L)) pilot generation processing on the transmitting side.

Fig. 5 is an explanatory diagram of the offset of the subcarrier mapping section.

Fig. 6 is an explanatory diagram of channel estimation processing on the receiving side.

Fig. 7 is a diagram illustrating the 2 nd pilot generation process.

Fig. 8 is an explanatory diagram of a copy method on the transmission side.

Fig. 9 is an explanatory diagram of the 2 nd channel estimation processing on the receiving side.

Fig. 10 is a frame structure diagram.

Fig. 11 is an explanatory diagram of the pilot separation method.

Fig. 12 is a diagram illustrating the 3 rd channel estimation process on the receiving side.

Fig. 13 is a block diagram of a mobile station.

Fig. 14 is a configuration diagram of a pilot generation unit.

Fig. 15 is a structural diagram of a base station.

Fig. 16 is a block diagram of a channel estimation unit.

Fig. 17 is a configuration diagram of a channel generation unit and a channel estimation unit that perform the 2 nd channel generation process and the channel estimation process.

Fig. 18 is a configuration diagram of a channel generation unit and a channel estimation unit that perform the 3 rd channel generation process and the channel estimation process.

Fig. 19 is an explanatory diagram of frequency allocation when the number of multiplexes is 4.

Fig. 20 is an explanatory diagram of hopping control for switching transmission bands allocated to respective users for each frame, and is an explanatory diagram of allocation in odd-numbered frames.

Fig. 21 is an explanatory diagram of hopping control for switching transmission bands allocated to respective users for each frame, and is an explanatory diagram of allocation in an even-numbered frame.

Fig. 22 is a configuration diagram of a pilot generation unit in performing hopping control.

Fig. 23 is a frame format example of single carrier transmission.

Fig. 24 is an explanatory diagram of frequency equalization.

Fig. 25 is a configuration diagram of an SC-FDMA transmitter.

Fig. 26 is an explanatory diagram of interference between cells.

Fig. 27 is a 1 st explanatory diagram of a conventional data transmission band and a pilot transmission band.

Fig. 28 is a 2 nd explanatory diagram of a conventional data transmission band and a pilot transmission band.

Detailed Description

(A) Principle of the invention

As shown in FIG. 1 (A), a pair of CAZAC sequences ZC_k(n) the result of cyclic shift c1 is used as pilot for user 1, and the CAZAC sequence ZC is used_kIf the result of (n) cyclic shift c2 is used as the pilot of user 2, subcarriers 23 and 24 are shifted from the pilot transmission band in the data transmission band of user 2, as described in fig. 28, and the channel estimation accuracy of the subcarriers deteriorates. In addition, in FIG. 1, DFT { ZC_k（n－c1）}、DFT{ZC_k(n-c 2) } is the CAZAC sequence ZC, for L ═ 11 respectively_k(n) performing cyclic shifts c1, c2, and then on ZC_k（n－c1）、ZC_k（n－c2) And performing DFT processing on the pilot frequency of the obtained frequency region.

Therefore, as shown in fig. 1 (B), when multiplexing is performed with a pilot having a frequency offset for each user in accordance with the transmission band of data, the transmission band of the pilot always covers the transmission band of data. In the example of FIG. 1 (B), the pilot DFT { ZC ] of user 2 is set_k(n-c 2) is offset by 1 subcarrier.

However, after pilot DFT { ZC }is used_k(n-c 2) is offset, pilot and replica of known pilot ZC are received on the receiving side_kThe correlation between (n) is τ c2, and a peak is not formed, and the peak position is deviated, so that the pilot cannot be correctly restored, and as a result, channel estimation cannot be performed. The reason for the deviation of the correlation peak position is explained below.

Relation of frequency offset to cyclic shift of time domain

First, the relationship between the frequency offset and the cyclic shift in the time domain is described. If the pair is CAZAC sequence ZC_kIf f (m) is the result of DFT conversion, f (m) can be expressed by the following expression.

When the following equations (7) and (4) are used for the transformation, the following equations hold.

Wherein,

kc≡d(modL)，θ_k，c＝πk/L·(c²-2qc-c·L％2)

in addition, d (modL) is the remainder of d divided by L.

As can be seen from equation (8), applying cyclic shift c to the CAZAC sequence in the time domain is equivalent to applying phase rotation of cyclic shifts of d subcarriers in the frequency domain. Where k and L are mutually prime and c (< L) is uniquely determined from k and d. In order to easily understand that c is determined by k, d, and L, c is newly set to s (k, d, and L). Table 1 shows c values corresponding to various combinations of s (k, d, L) and k when L is 11. For example, if k is 1, d is 1, and L11, c is 1, and if k is 2, d is 1, and L11, c is 6.

(Table 1)

S (k, d, L) when L is 11

k	s(k，1，11)	s(k，2，11)	s(k，3，11)
				1	1	2	3
2	6	1	7
				3	4	8	1
4	3	6	9
				5	9	7	5
6	2	4	6
				7	8	5	2
8	7	3	10
				9	5	10	4
10	10	9	8

As described above, applying a frequency offset of 1 subcarrier to pilot 2 as shown in fig. 2 (a) corresponds to moving component p11 in subcarrier 1 to subcarrier 12 after applying a cyclic shift of 1 subcarrier in the frequency domain as shown in fig. 2 (B). As a result, the correlation peak position of pilot 2 (see equation (5)) is shifted by s (k, d, L) (τ ═ c2+ s (k, d, L)) by equation (8). Since the correlation peak position (τ ═ c 1) of pilot 1 is not shifted, the correlation peak positions of pilot 2 and pilot 1 change by s (k, d ═ 1, and L ═ 11), and the pilot cannot be restored correctly on the receiving side, and as a result, channel estimation cannot be performed.

The cyclic shift amount is set from c so that the correlation peak position is the position described in the past₂Change to (c)₂-s (k, d, L)). That is, as shown in fig. 3 (a), if frequency offset d subcarriers (d ═ 1 in the figure) and cyclic shift (c) are applied to pilot 2₂S (k, d, L)), the relationship of pilots 1, 2 is as shown in FIG. 3 (B). By performing the above processing, the correlation peak positions of pilots 1 and 2 are not shifted, and the pilots can be accurately restored on the receiving side, thereby improving the channel estimation accuracy. That is, as before the frequency offset described in fig. 1 a, pilot 1 and pilot 2 may be separated according to the position of the correlation peak (τ c1, τ c 2).

(a) 1 st pilot generation process and channel estimation process

FIG. 4 is a diagram of the frequency offset d subcarriers and cyclic shift (c) used to implement the method illustrated in FIG. 3₂-s (k, d, L)) pilot generation processing on the transmitting side.

The CAZAC sequence generating unit 11 generates, for example, a CAZAC sequence ZC of L11_k(n) as pilot, the cyclic shift section 12 makes the CAZAC sequence ZC_k(n) Cyclic Shift c₂-s (k, d, L) generating ZC_k（n－c₂+ s (k, d, L)), and is input to the DFT section 13. N is a radical of_TXSize (N)_TXL11) to ZC by DFT section 13_k（n－c₂+ s (k, d, L)) is subjected to DFT operation to generate pilot DFT { ZC }_k（n－c₂+ s (k, d, L)) }. The subcarrier mapping section 14 offsets the 11 pilot components p1 to p11 in the frequency domain by d subcarriers (in the figure, d is 1), and inputs the offset to the IFFT section 15.

Fig. 5 is an explanatory diagram of the offset of the subcarrier mapping unit 14, where (a) shows a case where there is no offset (d is 0), and the subcarrier mapping unit 14 outputs the frequency f to the IFFT unit 15_i、f_i＋1、f_i＋2、、、f_i＋10The 11 pilot components p1 to p11 are input to the terminal(s) of (1), and 0 is input to the other terminals. (B) When there is an offset (d is 1), the subcarrier mapping section 14 maps the frequency f of the IFFT section 15 to the subcarrier_i+1、f_i＋2、f_i＋3、、、f_i+11The 11 pilot components p1 to p11 are input to the terminal(s) of (1), and 0 is input to the other terminals. N is a radical of_FFTSize (e.g. N)_FFT128) performs IDFT operation processing on the input subcarrier component to convert the subcarrier component into a time domain signal, and the CP (cyclic prefix) insertion unit 16 adds a cyclic prefix for interference prevention and outputs the cyclic prefix. (C) Other embodiments are possible with an offset (d ═ 1). In this case, the cyclic shift section 12 makes the CAZAC sequence ZC_k(n) Cyclic Shift c₂To generate ZC_k(n-c 2) is input to the DFT unit 13. DFT section 13 pairs ZC_k(n-c 2) performs DFT operation to generate pilot DFT { ZC }_k(n-c 2). Subcarrier mapping section 14 to IFFT section f_i+1、f_i＋2、、、f_i＋10The pilot components p2 to p11 are input to the terminal of (1), and the input signals are applied to an IFFT unit f_i＋11The terminal of which inputs the pilot component p 1.

Pilot 1 and pilot 2 (see fig. 3B) transmitted from user 1 and user 2 are multiplexed in the air and used as subcarrier frequency f_i、f_i＋1、f_i＋2、f_i＋3、、、f_i+11The subcarrier components (p 1 to p 12) are input to a channel estimation unit. The subcarrier adding section 52 adds the subcarrier components p12 and p1 which do not overlap with each other, and takes the addition result as a subcarrier component p1 of a new subcarrier frequency f 1.

The replica signal multiplication unit 53 multiplies a pilot replica signal (for a known CAZAC sequence ZC with a zero cyclic shift amount) by each subcarrier_k(n) the result of DFT computation) qi is multiplied by the received pilot signal pi, and the IDFT unit 54 performs IDFT computation on the result of replica multiplication to output a delay profile in the time domain. Since the delay profile in the time domain is a sample of length L and has a correlation peak at t ═ c1 and t ═ c2, the profile extraction unit 55 separates the correlation peak from t ═ c1 + c 2)/2 to generate profiles PRF1 and PRF2 of samples of length L/2 for users 1 and 2. The L-size DFT unit 56a inserts L/4 zeros on both sides of the L/2-length profile PRF1, thereby forming a length L, and performs DFT computation. Thereby, the DFT unit 56a can obtain the subcarrier frequency f_i、f_i＋1、f_i＋2、、、f_i＋10The channel estimation values h 1-h 11 of user 1. Similarly, the L-size DFT unit 56b inserts L/4 zeros on both sides of the L/2 sample length contour PRF2, thereby forming a length L, and performs DFT computation. Thereby, the DFT unit 56b can obtain the subcarrier frequency f_i＋1、f_i＋2、f_i＋3、、、f_i＋11The channel estimation values h 2-h 12 of user 2. In the subcarrier adding section 52, p1 and p2 are added as the subcarrier frequency f_iSo that the subcarrier frequency f outputted from the DFT section 56b is transmitted_iAs the subcarrier frequency f_i＋11H 12.

From the above, if the distortion due to the propagation conditions is small for pilot 1 and pilot 2, respectively, the components that do not overlap with each other are added on the receiving side, multiplied by a replica, and then separated in a completely orthogonal form in the delay profile in the time domain, as shown in fig. 6. When the distortion caused by the propagation condition is large, the subcarrier addition can be omitted, and the replica is directly multiplied and then separated in the delay profile of the time domain.

(b) 2 nd pilot generation process and channel estimation process

In the above-described 1 st pilot estimation process, the subcarrier components p12 and p1 which do not overlap with each other are added, and the addition result is regarded as the subcarrier frequency f_iThe component (c). However, if the subcarrier frequency f of the received signal is_iHas beenThe sum of p12 and p1 eliminates the need to add subcarriers at the receiving side.

Fig. 7 is an explanatory view of the 2 nd pilot generation process, where (a) shows data subcarriers of user 1 and user 2.

The transmitting side (user 1) transmits the subcarrier frequency f of pilot 1 as shown in fig. 7 (B)_iIs copied into subcarrier frequency f_i＋11And as shown in fig. 7 (C), user 2 will pilot the subcarrier frequency f of pilot 2_i＋11Is copied into subcarrier frequency f_iThe subcarrier component of (a) is transmitted. Thus, as shown in fig. 7 (D), these pilots are multiplexed and received by the receiving side, and the carrier component of the subcarrier frequency f1 of the received signal is a value obtained by adding p1 and p12, and the carrier component of the subcarrier frequency is also a value obtained by adding p1 and p12, and the subcarrier addition by the receiving side is not necessary.

Fig. 8 is an explanatory diagram of a transmission side duplication method, where (a) is a duplication method of pilot 1 of user 1, and the subcarrier mapping section 14 further transmits the frequency f to the IFFT section 15_i+11Terminal of (2) input pilot 1 subcarrier frequency f_iSuch that the subcarrier frequency f of the pilot 1 is_iMay also be the subcarrier frequency f_i＋11The subcarrier component of (a). (B) The pilot 2 of the user 2 is copied, and the subcarrier mapping part 14 also sends the frequency f to the IFFT part 15_iTerminal of (2) input pilot 12, subcarrier frequency f_i＋11Such that the subcarrier frequency f of the pilot 12 is_i＋11May also be the subcarrier frequency f_iThe subcarrier component of (a). (C) Another embodiment of the pilot 2 duplication method for user 2 corresponds to fig. 5 (C).

Fig. 9 is an explanatory diagram of channel estimation processing on the receiving side. Pilot 1 and pilot 2 (see fig. 7 (B) and (C)) transmitted from user 1 and user 2, respectively, are multiplexed in the air and regarded as subcarrier frequency f_i、f_i＋1、f_i＋2、f_i＋3、、、f_i+11The subcarrier components (p 1 to p 12) are input to the channel estimation unit (fig. 7D).

The replica signal multiplication section 53 for user 1 multiplies the received pilot signal pi (p 1 to p 11) by the replica signal qi (q 1 to q 11) for pilot for each subcarrier, and then the IDFT section 54, the correlation separation section 55, and the DFT section 56 perform the same processing as shown in fig. 6, thereby generating channel estimation values h1 to h11 for user 1.

On the other hand, the replica signal multiplying unit 53 'for user 2 multiplies the received pilot signal pi (p 2 to p 12) by the replica signal qi (q 1 to q 11) for pilot for each subcarrier, and then the IDFT unit 54', the correlation separation unit 55', and the DFT unit 56' perform the same processing as that for user 1, thereby generating channel estimation values h2 to h12 for user 2.

(c) 3 rd pilot generation process and channel estimation process

In the 1 st channel estimation process, the correlation separation section 55 separates the pilot component of user 1 and the pilot component of user 2, but as shown in fig. 10, when 1 frame contains, for example, 2 pilot blocks, separation may be performed as follows. Fig. 11 is an explanatory diagram of the pilot separation method, where (a) shows data subcarriers of user 1 and user 2.

First pilot 1 to user 1 and user 2 (═ DFT { ZC)_k(n-c 1)), pilot 2 (═ DFT { ZC) })_kEach subcarrier component of (n-C2+ s (k, D, L)) }) is multiplied by +1 as shown in (B) and (C) and transmitted to each subcarrier component of the next pilot 1 and pilot 2 as shown in (D) and (E) multiplied by +1 and-1, respectively.

Thus, the receiving side receives the following pilot multiplexed signal first,

DFT{ZC_k(n-c1)}×(+1)+DFT{ZC_k(n-c2+ s (k, d, L)) × (+1) then receives the following pilot multiplexed signal.

DFT{ZC_k(n-c1)}×(+1)+DFT{ZC_k(n-c2+s(k,d,L))×(-1)

Therefore, in order to generate the pilot of user 1 on the receiving side, the next pilot multiplex signal may be added to the first pilot multiplex signal. That is, since pilot 2 has a different polarity, pilot 2 is canceled by addition, leaving pilot 1. Then, in order to generate the pilot of user 2 on the receiving side, the next pilot multiplex signal may be subtracted from the first pilot multiplex signal. That is, since pilot 1 has the same polarity, pilot 1 is canceled by subtraction, leaving pilot 2.

Fig. 12 is an explanatory diagram of channel estimation processing on the receiving side. Pilot 1 and pilot 2 (see fig. 11 (B) and (C); (D) and (E)) transmitted from user 1 and user 2, respectively, are multiplexed in the air and treated as subcarrier frequency f_i、f_i＋1、f_i＋2、f_i＋3、、、f_i+11The subcarrier components (p 1 to p 12) are input to a channel estimation unit.

The inter-block subcarrier calculation unit 61 receives and stores the 1 st received pilot signal. When the pilot of user 1 is generated, if the 2 nd reception pilot signal is received, the inter-block subcarrier calculation unit 61 adds the 1 st and 2 nd reception pilot signals for each subcarrier to generate the subcarrier frequency f of pilot 1_i、f_i＋1、f_i＋2、f_i＋3、、、f_i＋10Carrier components p1 to p 11. The replica signal multiplication section 53 for user 1 multiplies the received pilot signal pi (p 1 to p 11) by the replica signal qi (q 1 to q 11) for pilot for each subcarrier, and then the IDFT section 54, the correlation separation section 55, and the DFT section 56 perform the same processing as shown in fig. 6, thereby generating channel estimation values h1 to h11 for user 1. Although the accuracy is lowered, the result of multiplying the replica signals may be used as the channel estimation values h1 to h 11.

On the other hand, when the pilot of user 2 is generated, the inter-block subcarrier calculating unit 61 subtracts the 1 st and 2 nd received pilot signals for each subcarrier to generate the subcarrier frequency f of pilot 2_i+1、f_i＋2、f_i＋3、、、f_i+11Carrier component p2 ℃p 12. The replica signal multiplying unit 53 'for user 2 multiplies the received pilot signal pi (p 2 to p 12) by the replica signal qi (q 1 to q 11) for pilot for each subcarrier, and then the IDFT unit 54', the correlation separation unit 55', and the DFT unit 56' perform the same processing as that for user 1, thereby generating channel estimation values h2 to h12 for user 2.

In the above description, the number of pilot blocks is 2, but the 3 rd pilot generation process and the channel estimation process can be applied even when the number of pilot blocks is an even number. In this case, the base station instructs a certain user terminal to multiply +1 to the pilot signals of all blocks, and instructs other user terminals to multiply +1 to half of the pilot signals and-1 to the remaining half of the pilot signals. When the base station multiplexes and receives the pilot signals transmitted from the user terminals, the base station performs addition and subtraction processing on the pilot signals of all blocks so that only the pilot signal from a predetermined user terminal (user terminal 1 or 2) remains, multiplies the result of the operation by a replica of the pilot signal, converts the result of the replica multiplication into a time domain signal, and separates a signal portion of the user terminal from the time domain signal to perform channel estimation.

(B) Mobile station

Fig. 13 is a block diagram of a mobile station.

When uplink transmission data is generated, a mobile station (user terminal) requests a base station for resource allocation, and the base station allocates resources according to the request and the transmission path state of the mobile station, and notifies the mobile station of resource allocation information. The mobile station transmits the notified data and pilot. That is, the radio unit 21 converts a radio signal received from the base station into a baseband signal, and inputs the baseband signal to the received signal baseband processing unit 22. The baseband processing section 22 separates data and other control information from the received signal, and also separates resource allocation information and inputs the separated information to the transmission resource management section 23. The resource allocation information includes a transmission band of pilot, a sequence number and a sequence length L of a CAZAC sequence used as pilot, a cyclic shift amount, a frequency offset amount d, and the like, in addition to a transmission band of data, timing, a modulation scheme, and the like.

The transmission resource management unit 23 inputs information necessary for the transmission processing of data and control information to the data processing unit 24, and inputs information necessary for the pilot generation/transmission processing to the pilot generation unit 25. The data processing unit 24 performs data modulation and single carrier transmission processing on data and control information based on information input from the transmission resource management unit 23, and outputs the data and control information, the pilot generation unit 25 generates a pilot by performing processing such as CAZAC sequence generation, cyclic shift, and frequency offset in accordance with an instruction from the transmission resource management unit 23, and the frame generation unit 26 generates a frame by time-multiplexing 6 data blocks and 2 pilot blocks as shown in fig. 10, for example, and transmits the frame from the radio unit 21 to the base station.

Fig. 14 is a configuration diagram of the pilot generation unit 25, which is a configuration diagram when the pilot is generated according to the 1 st pilot generation process described in fig. 3, (a) is a configuration diagram of performing cyclic shift before DFT, and (B) is a configuration diagram of performing cyclic shift after IFFT.

In fig. 14 a, the transmission resource management unit 23 inputs parameters (CAZAC sequence number, sequence length, cyclic shift amount, and frequency offset) necessary for pilot generation and transmission included in the resource allocation information received from the base station to each section.

The CAZAC sequence generating unit 11 generates a designated CAZAC sequence ZC having a sequence length L and a sequence number_k(n) as pilot, the cyclic shift section 12 makes the CAZAC sequence ZC_k(n) cyclically shifting the indicated c samples, resulting in a ZC_k(n-c) is inputted to the DFT unit 13. For example, if it is pilot 1 in fig. 3 (B), the cyclic shift section 12 makes ZC_k(n) a shift of c1 to generate ZC_k(n-c 1), if Pilot 2, cyclic shift c₂S (k, d, L) to produce ZC_k(n-c2+ s (k, d, L)), and input to the DFT unit 13. N is a radical of_TXSize (N)_TXL) to the input pilot ZC_k(n-c) performing DFT operation to generate pilot DFT { ZC ] of frequency region_k(n-c). The subcarrier mapping section 14 controls the mapping position of the pilot frequency based on the instructed frequency offset dMaking a frequency offset, N_FFTSize (N)_FFT128), the IFFT section 15 performs IFFT processing on the input subcarrier component, converts the result into a time domain signal, and inputs the signal to the input frame generation section 26.

Fig. 14 (B) is a configuration diagram of the pilot generator 25 in the case of performing cyclic shift after IFFT, and the cyclic shift unit 12 performs cyclic shift c × N_FFT/N_TXAnd thus exactly the same result as that of fig. 14 (a) can be obtained.

(C) Base station

Fig. 15 is a structural diagram of a base station.

When uplink transmission data is generated, a mobile station (user) performs a step of establishing a communication link between the mobile station and a base station, and transmits a transmission path situation to the base station in the course of performing the step. That is, the mobile station receives the shared pilot transmitted from the base station, performs radio measurement (SIR or SNR measurement), and reports the radio measurement result to the base station as the propagation path condition. For example, the base station divides the transmission band into a plurality of transmission bands, transmits the shared pilot for each transmission band, and the mobile station performs radio measurement for each transmission band and transmits the measurement result to the base station. The base station acquires the transmission path situation from the mobile station, allocates resources according to the transmission path situation of the mobile station when receiving the resource allocation request, and sends the resource allocation information to the mobile station.

The radio unit 31 converts a radio signal received from a mobile station into a baseband signal, the demultiplexing unit 32 demultiplexes data/control information and pilot, inputs the data/control information to the data processing unit 33, and inputs the pilot to the channel estimation unit 34. The data processing unit 33 and the channel estimation unit 34 have a frequency equalization structure shown in fig. 24.

When establishing a communication link, the data processing unit 33 demodulates the propagation path condition data transmitted from the mobile station, and inputs the data to the uplink (uplink) resource management unit 35. The uplink resource management unit 35 allocates resources according to the propagation path situation, generates resource allocation information, and inputs the resource allocation information to the downlink signal baseband processing unit 36. The resource allocation information includes a transmission band of pilot, a sequence number and a sequence length L of a CAZAC sequence used as pilot, a cyclic shift amount, a frequency offset amount d, and the like, in addition to a transmission band of data, timing, a modulation scheme, and the like. The downlink signal baseband processing section 36 time-division multiplexes the downlink data, the control information, and the resource allocation information, and transmits the result from the radio section 31.

Upon receiving the resource allocation information, the mobile station performs the processing described in fig. 13 and 14, and transmits a frame including data and pilot.

The channel estimation unit 34 performs the 1 st channel estimation process described with reference to fig. 6 using the pilot separated and input by the separation unit 32, and inputs the channel estimation value to the data processing unit 33. The data processing unit 33 performs channel compensation based on the channel estimation value and demodulates the data based on the channel compensation result. The uplink resource management unit 35 includes a cyclic shift amount calculation unit 35a and a link allocation information instruction unit 35 b.

Fig. 16 is a configuration diagram of the channel estimation unit 34, and the same components as those in fig. 6 are denoted by the same reference numerals.

The DFT unit 51 performs DFT computation processing on the pilot signals input from the separation unit 32, and converts the pilot signals into pilot signals in the frequency domain (subcarrier components p1 to p 12). The subcarrier adding section 52 adds the subcarrier components p12 and p1 that do not overlap each other, and takes the addition result as a subcarrier component p1 of a new subcarrier frequency f 1.

The replica signal multiplying unit 53 multiplies the received pilot signal pi by the replica signal qi of the pilot for each subcarrier, and the IDFT unit 54 performs IDFT operation processing on the result of the multiplication of the replicas to output a pilot signal in the time domain. The contour extraction unit 55 divides the IDFT output signal by t ═ c1 + c 2/2, and if the signal is a received signal from user 1, selects a contour PRF1 (see fig. 6), and the DFT unit 56 performs DFT computation on the contour PRF1 to output channel estimation values h1 to h 11. On the other hand, if the signal is a received signal from user 2, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs DFT computation on the profile PRF2 to output channel estimation values h2 to h 12.

(D) 2 nd pilot frequency generating part and channel estimating part

Fig. 17 (a) is a configuration diagram of a pilot generation unit that performs the 2 nd pilot generation process described in fig. 7, and the same parts as those of the pilot generation unit in fig. 14 (a) are denoted by the same reference numerals. The difference is that the subcarrier mapping unit 14 performs both the subcarrier mapping based on the frequency offset d and the copying of the pilot component of the predetermined subcarrier, and the other operations are the same.

The CAZAC sequence generating unit 11 generates a designated CAZAC sequence ZC having a sequence length L and a sequence number_k(n) as pilot, the cyclic shift section 12 transfers the CAZAC sequence ZC_k(n) cyclically shifting the indicated c samples, resulting in a ZC_k(n-c) is inputted to the DFT unit 13. For example, if it is pilot 1 for user 1 in fig. 7 (B), the cyclic shift section 12 makes ZC_k(n) a shift of c1 to generate ZC_k(n-c 1), if it is pilot 2 for user 2, cyclic shift c₂S (k, d, L) to produce ZC_k(n-c2+ s (k, d, L)), and input to the DFT unit 13. N is a radical of_TXSize (N)_TXL) to the input pilot ZC_k(n-c) performing DFT operation to generate pilot DFT { ZC ] of frequency region_k（n－c）}。

The subcarrier mapping section 14 performs subcarrier mapping based on the copy information and the frequency offset information instructed from the transmission resource management section 23. For example, the subcarrier mapping process shown in fig. 8 (a) is performed for pilot 1 of user 1 in fig. 7 (B), and the subcarrier mapping process shown in fig. 8 (B) is performed for pilot 2 of user 2 in fig. 7 (C). N is a radical of_FFTSize (e.g. N)_FFT128), the IFFT unit 15 performs IFFT processing on the input subcarrier component, converts the result into a pilot signal in the time domain, and inputs the pilot signal to the frame generation unit 26.

Fig. 17 (B) is a configuration diagram of the channel estimation unit 34 that performs the 2 nd channel estimation process described in fig. 9, and the same parts as those of the channel estimation unit in fig. 16 are denoted by the same reference numerals. The difference is that the multiplication processing by the subcarrier adding section 52 and replica signal multiplying section 53 is deleted.

The DFT unit 51 performs DFT computation processing on the pilot signals input from the demultiplexing unit 32, and converts the pilot signals into pilot signals in the frequency domain (subcarrier components p1 to p 12). Replica signal multiplying unit 53 receives pilot 1 from user 1, and outputs received pilot subcarrier f from DFT unit 51_i、f_i＋1、f_i＋2、f_i＋3、、、f_i＋10The components p1 to p11 and replica signals q1 to q11 are multiplied, and if pilot 2 from user 2 is received, pilot-received subcarrier f output from DFT section 51 is multiplied_i＋1、f_i＋2、f_i＋3、、、f_i+11The components p2 to p12 are multiplied by the replica signal.

Then, the IDFT unit 54 performs IDFT operation processing on the replica multiplication result, and outputs a delay profile in the time domain. The contour extraction unit 55 divides the IDFT output signal by t ═ c1 + c 2/2, selects a contour PRF1 (see fig. 6) if the IDFT output signal is a pilot signal from the user 2, and the DFT unit 56 performs DFT computation on the contour PRF1 to output channel estimation values h1 to h 11. On the other hand, if the signal is a received signal from user 1, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs DFT computation on the profile PRF2 to output channel estimation values h2 to h 12.

(E) 3 rd pilot frequency generating part and channel estimating part

Fig. 18 (a) is a configuration diagram of a pilot generation unit that performs the 3 rd pilot generation process described in fig. 11, and the same parts as those of the pilot generation unit in fig. 14 (a) are denoted by the same reference numerals. Except that the polarity adding section 61 is added, the other operations are the same.

The CAZAC sequence generating unit 11 generates a designated CAZAC sequence ZC having a sequence length L and a sequence number_k(n) as pilot, the cyclic shift section 12 transfers the CAZAC sequence ZC_k(n) cyclically shifting the indicated c samples, resulting in a ZC_k(n-c) is inputted to the DFT unit 13. For example, if pilot 1 is used for user 1 in FIGS. 11 (B) and (D),the cyclic shift section 12 makes ZC_k(n) a shift of c1 to generate ZC_k(n-c 1), if it is pilot 2 for user 2, cyclic shift c₂S (k, d, L) to produce ZC_k(n-c2+ s (k, d, L)), and input to the DFT unit 13. N is a radical of_TXSize (N)_TXL) to the input pilot ZC_k(n-c) performing DFT operation to generate pilot DFT { ZC ] of frequency region_k（n－c）}。

The subcarrier mapping section 14 performs subcarrier mapping based on the frequency offset information instructed from the transmission resource management section 23. The polarity adding section 61 adds the polarity instructed from the transmission resource management section 23 to the output of the subcarrier mapping section 14, and inputs the result to the IFFT section 15. For example, in case of pilot 1 for user 1, since the polarity of +1 is indicated in the 1 st and 2 nd pilot blocks (see fig. 11 (B) and (D)), the polarity adding section 61 multiplies all carrier components output from the subcarrier mapping section 14 by +1 and inputs the result to the IFFT section 15. Further, if pilot 2 for user 2 is used, since the polarity of +1 is indicated in the 1 st pilot block and the polarity of-1 is indicated in the 2 nd pilot block (see fig. 11 (C) and (E)), the polarity adding unit 61 multiplies the 1 st pilot block by +1 and inputs the result to the IFFT unit 15, and multiplies the 2 nd pilot block by-1 and inputs the result to the IFFT unit 15, for all carrier components output from the subcarrier mapping unit 14.

N_FFTSize (N)_FFT128), the IFFT unit 15 performs IFFT processing on the input subcarrier component, converts the result into a pilot signal in the time domain, and inputs the pilot signal to the frame generation unit 26.

Fig. 18 (B) is a configuration diagram of the channel estimation unit 34 that performs the 3 rd channel estimation process described in fig. 12, and the same parts as those of the channel estimation unit in fig. 16 are denoted by the same reference numerals. Except that the inter-block subcarrier adding section 62 is provided instead of the subcarrier adding section 52.

The DFT unit 51 performs DFT processing on the pilot signal of the 1 st pilot block input from the demultiplexing unit 32, converts the pilot signal into pilot signals (subcarrier components p1 to p 12) in the frequency domain, and the inter-block subcarrier adding unit 62 stores the pilot signals (subcarrier components p1 to p 12) in an internal memory. Then, DFT section 51 performs DFT operation on the pilot signal of the 2 nd pilot block input from demultiplexing section 32, converts the signal into pilot signals in the frequency domain (subcarrier components p1 to p 12), and inputs the signal to inter-block subcarrier adding section 62.

The inter-block subcarrier adding section 62, if receiving pilot 1 from user 1, adds the pilot signals (subcarrier components p1 to p 12) of the 1 st pilot block and the pilot signals (subcarrier components p1 to p 12) of the 2 nd pilot block, which are held, for each subcarrier. Thereby removing the multiplexed pilot signal components from other users (e.g., user 2). Then, if pilot 2 from user 2 is received, inter-block subcarrier addition section 62 subtracts the pilot signals (subcarrier components p1 to p 12) of the 2 nd pilot block from the pilot signals (subcarrier components p1 to p 12) of the 1 st pilot block stored for each subcarrier. Thereby removing the multiplexed pilot signal components from other users (e.g., user 1).

Upon receiving pilot 1 from user 1, replica signal multiplying unit 53 adds sub-carrier f of the received pilot output from inter-block sub-carrier adding unit 62_i、f_i＋1、f_i＋2、f_i＋3、、、f_i＋10Multiplies the components p1 to p11 by replica signals q1 to q11, and if pilot 2 is received from user 2, adds the pilot-received subcarrier f output from the inter-block subcarrier adding section 62_i＋1、f_i＋2、f_i＋3、、、f_i+11The components p2 to p12 and the replica signals q1 to q 11.

Then, the IDFT unit 54 performs IDFT operation processing on the replica multiplication result, and outputs a pilot signal in the time domain. The contour extraction unit 55 divides the IDFT output signal by t ═ c1 + c 2/2, selects a contour PRF1 (see fig. 6) if the IDFT output signal is a pilot signal from user 1, and the DFT unit 56 performs DFT computation on the contour PRF1 to output channel estimation values h1 to h 11. On the other hand, if the signal is a received signal from user 2, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs DFT computation on the profile PRF2 to output channel estimation values h2 to h 12.

(F) Adaptive control

As described above, the uplink resource management unit 35 (fig. 15) of the base station specifies the transmission band of the pilot, the CAZAC sequence number and sequence length L, the cyclic shift amount, the frequency offset d, and the like according to the propagation path situation of the mobile station, and notifies the mobile station of the specified transmission band, the CAZAC sequence number, the sequence length L, the cyclic shift amount, the frequency offset d, and the like. The uplink resource management unit 35 of the base station also determines the number of multiplexes in the transmission band based on the propagation path situation of each mobile station.

Fig. 19 is an explanatory diagram of frequency allocation when the number of multiplexes is 4, in which first 12 subcarriers are allocated to user 1, second 12 subcarriers are allocated to user 2, third 12 subcarriers are allocated to user 3, and third 12 subcarriers are allocated to user 4, and in this case, the cyclic shift amount is changed to use the CAZAC sequence ZC having a sequence length L of 19_kAnd (n) as pilots for each user.

The frequency offset of the pilot is set to cover the data transmission frequency bandwidth of each user as much as possible. The cyclic shift calculation unit 35a (fig. 15) calculates the cyclic shift amount for each user according to the following equation.

c_i＝c_p-s(k，d，L) (9)

Wherein i and p respectively represent a data transmission band number and a user number. S (k, d, L) represents a cyclic shift amount generated from the sequence number k, the sequence length L, and the frequency offset, and the relationship shown in the following equation holds.

k·s(k，d，L)≡d(modL) (10)

C of p-th user_pFor example, the following equation can be used for calculation.

c_p＝(p-1)×[L/P]p＝1，2，，P (11)

P represents the number of pilot bits (number of users) multiplexed by cyclic shift. In the case shown in fig. 19, cyclic shift amount c of user 1 to user 4₁～c₄As follows.

c₁＝0

c₂＝[L/4]

c₃＝[2·L/4]-s(k，d，L)

c₄＝[3·L/4]-s(k，d，L)

However, depending on the pilot signal reception scheme, the channel estimation characteristics at both ends of the pilot transmission band may deteriorate, and the channel estimation characteristics at the middle portion may be good. That is, as shown in fig. 19, the channel estimation accuracy may deteriorate in the transmission bands of subcarriers 1 to 12 and 37 to 48, and the channel estimation accuracy may be good in the transmission bands of subcarriers 13 to 24 and 25 to 36.

Therefore, the transmission bands of the middle subcarriers 13 to 24 and 25 to 36 are preferentially allocated to users with poor propagation path conditions, and the transmission bands of the subcarriers 1 to 12 and 37 to 48 on both sides are allocated to users with good propagation path conditions. In this way, users whose channel estimation accuracy is extremely deteriorated are eliminated. Fig. 19 shows an example in which the intermediate transmission bands are allocated to the users 2 and 3.

Control (hopping control) shown in fig. 20 and 21 may be performed to switch the transmission band allocated to each user for each frame. Fig. 20 is an explanatory diagram of allocation in odd-numbered frames, and fig. 21 is an explanatory diagram of allocation in even-numbered frames.

In the odd-numbered frames, as shown in fig. 20, subcarriers 1 to 12 and 37 to 48 on both sides are allocated to user 1 and user 4, and subcarriers 13 to 24 and 25 to 36 in the middle are allocated to user 2 and user 3. In the even-numbered frames, as shown in fig. 21, the subcarriers 13 to 24 and 25 to 36 in the middle are allocated to the user 4 and the user 1, and the subcarriers 1 to 12 and 37 to 48 on both sides are allocated to the user 3 and the user 2. In addition, in the odd-numbered frames, the pilots of the user 3 and the user 4 are multiplied by the frequency offset, and in the even-numbered frames, the pilots of the user 1 and the user 2 are multiplied by the frequency offset. In this way, users whose channel estimation accuracy is extremely deteriorated are eliminated.

Fig. 22 is a configuration diagram of a pilot generation unit for performing hopping control, and the same parts as those of the pilot generation unit in fig. 14 (a) are denoted by the same reference numerals. Except that the frequency offset switching control section 71 is added, the other operations are the same.

The CAZAC sequence generating unit 11 generates a designated CAZAC sequence ZC having a sequence length L and a sequence number_k(n) as pilot, the cyclic shift section 12 makes the CAZAC sequence ZC_k(n) cyclically shifting the indicated c samples, resulting in a ZC_k(n-c) is inputted to the DFT unit 13. N is a radical of_TXSize (N)_TXL) to the input pilot ZC_k(n-c) performing DFT operation to generate pilot DFT { ZC ] of frequency region_k(n-c). The frequency offset switching control section 71 determines whether or not to perform frequency offset based on the frequency offset amount d and the hopping pattern instructed by the transmission resource management section 23. The subcarrier mapping section 14 performs subcarrier mapping depending on whether or not frequency offset is to be performed. N is a radical of_FFTSize (N)_FFT128), the IFFT unit 15 performs IDFT operation processing on the input subcarrier component, converts the result into a pilot signal in the time domain, and inputs the pilot signal to the frame generation unit 26.

Effect of the invention

According to the present invention described above, it is possible to perform channel estimation of data transmission subcarriers shifted from the pilot transmission band with high accuracy.

Also, according to the present invention, even if a predetermined sequence (e.g., CAZAC sequence ZC) is used_k(n)) the result of applying different amounts of cyclic shifts is used as the pilot of the user to be multiplexed, and channel estimation of the subcarriers allocated to each user can be performed with high accuracy.

Further, according to the present invention, even if the result of performing cyclic shifts of different amounts on a predetermined sequence is used as the pilot of the user to be multiplexed, the pilot of each user can be separated by a simple method and channel estimation can be performed.

Further, according to the present invention, by preferentially allocating the middle part of the transmission band of the pilot to the user whose channel condition is poor, it is possible to improve the channel estimation accuracy of the data transmission subcarriers of the user even for the user whose channel condition is poor.

Further, according to the present invention, the data transmission band allocated to the user is hopped between the middle portion and the edge portion of the pilot transmission band, and it is possible to improve the channel estimation accuracy of the transmission data subcarriers of the user even for the user whose transmission path condition is not good.

Claims

1. A wireless communication method for transmitting data of a 1 st user and a 2 nd user by using a 1 st subcarrier group and a 2 nd subcarrier group, respectively, and multiplexing pilot signals of the 1 st user and the 2 nd user for the data to transmit, the wireless communication method being characterized in that,

when pilot signals of the 1 st and 2 nd users generated by applying cyclic shift to the CAZAC sequence having the sequence length L are arranged at different frequencies,

for the pilot signal of the 1 st user, the ith sub-carrier frequency on the low frequency band side of the transmission frequency band is usedRate f_iIs replicated to the i + L sub-carrier frequency f on the high band side_i+LThe sub-carrier components of (a) are,

for the pilot signal of the 2 nd user, i + L sub-carrier frequency f on the high frequency band side of the transmission band_i+LIs copied to the ith subcarrier frequency f on the low band side_iOr the ith subcarrier frequency f on the low-band side of the transmission band_iIs replicated to the i + L sub-carrier frequency f on the high band side_i+LThe subcarrier component of (a).

2. A wireless communication method for transmitting data of a 1 st user terminal and a 2 nd user terminal to a base station using a 1 st subcarrier group and a 2 nd subcarrier group, respectively, and multiplexing pilot signals of the 1 st user terminal and the 2 nd user terminal for the data to transmit, the wireless communication method being characterized in that,

when the 1 st and 2 nd user terminals place pilot signals of the 1 st and 2 nd users generated by applying cyclic shift to the CAZAC sequence having the sequence length L on different frequencies from each other,

for the pilot signal of the 1 st user, the ith subcarrier frequency f on the low frequency band side of the transmission band_iIs replicated to the i + L sub-carrier frequency f on the high band side_i+LThe sub-carrier components of (a) are,

for the pilot signal of the 2 nd user, i + L sub-carrier frequency f on the high frequency band side of the transmission band_i+LIs copied to the ith subcarrier frequency f on the low band side_iOr the ith subcarrier frequency f on the low-band side of the transmission band_iIs replicated to the i + L sub-carrier frequency f on the high band side_i+LThe sub-carrier components of (a) are,

and the base station receives a signal obtained by multiplexing pilot signals of the 1 st user and the 2 nd user to the data of the 1 st user terminal and the 2 nd user terminal.