CN113079122A - Design method for truncating and extrapolating pilot frequency sequence in reconstructed multi-carrier signal - Google Patents
Design method for truncating and extrapolating pilot frequency sequence in reconstructed multi-carrier signal Download PDFInfo
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Abstract
A design method for truncating and extrapolating a pilot sequence in a reconstructed multi-carrier signal belongs to the technical field of wireless communication. The invention solves the problem that the compressed pilot frequency can not eliminate self-interference after being reconstructed in a compressed OFDM system adopting the traditional pilot frequency, thereby causing poor accuracy of channel estimation. Aiming at the problem that self-interference introduced by a compressed OFDM transmission method influences the accuracy of pilot frequency assisted channel estimation, the distortion degree of compressed pilot frequency is reduced and the accuracy of channel estimation is improved by designing a pilot frequency sequence with null points. The invention can be applied to the design of truncating and extrapolating the pilot frequency sequence in the reconstructed multi-carrier signal.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a design method for truncating and extrapolating a pilot frequency sequence in a reconstructed multi-carrier signal.
Background
With the increasing development of communication systems, the demand of mass data on communication resources is increased, and the demand of a 5G communication high-throughput scene on efficient transmission promotes the development of a series of high-spectrum-efficiency transmission technologies such as signal coding, modulation technology, filter design and the like. For the OFDM system, since the orthogonal system satisfies the nyquist criterion, the communication efficiency is mainly improved by increasing the modulation order, reducing the cyclic prefix, the guard interval, or reducing the out-of-band radiation, but these approaches also have corresponding limitations. For example, higher order modulation makes the signal more sensitive to noise and more demanding on the communication device. In addition, these techniques also fail to achieve increased transmission efficiency from the symbol level. Therefore, a truncation and extrapolation reconstruction method for the OFDM signal is developed, and the method is a new efficient transmission method formed by combining the band-limited signal extrapolation idea based on the band-limited (band-limited) characteristic of the OFDM signal. At a transmitting end, cutting off an original OFDM signal and transmitting the original OFDM signal; at a receiving end, the whole OFDM signal is reconstructed by repeatedly applying iterative processes of Fourier transform, inverse transform, filtering and replacement to a part of received signals. The method can improve the communication efficiency at the cost and on the premise that the original signal is cut off by the sending end and self-interference is introduced, but the reconstruction process of the receiving end recovers the signal based on an extrapolation method and the signal distortion caused by the self-interference is reduced as much as possible.
As is known, channel estimation is the basis for the subsequent signal detection and decoding process, and is more accurate in the truncation and extrapolation reconstruction of multicarrier transmission. Pilots commonly used for OFDM channel estimation include block pilots, comb pilots, and the like. The block pilot frequency can be regarded as a complete OFDM symbol, all subcarriers of each OFDM symbol are used for transmitting the pilot frequency symbol, and the block pilot frequency can accurately estimate the channel information on each subcarrier in the bandwidth and is suitable for a frequency selective channel; the comb pilot can adapt to the change of fast time-varying channel, but needs to get the channel information in the whole frequency band by interpolation method. For compressed OFDM systems, pilot-assisted channel estimation methods may also be employed. If the pilot signal and the transmitted data are compressed and transmitted together, self-interference on the frequency point where the pilot signal is located is inevitably generated, and the self-interference can generate influence on a channel estimation result, which is difficult to eliminate.
Disclosure of Invention
The invention aims to solve the problem that the compressed pilot frequency cannot eliminate self-interference after being reconstructed in a compressed OFDM system adopting the traditional pilot frequency, so that the accuracy of channel estimation is poor, and provides a design method for truncating and extrapolating a pilot frequency sequence in a reconstructed multi-carrier signal.
The technical scheme adopted by the invention for solving the technical problems is as follows:
based on one aspect of the present invention, a method for designing a pilot sequence in a truncated and extrapolated reconstructed multi-carrier signal includes the following steps:
at the transmitting end
Step one, generating a group of N-lengthpThe generated comb-shaped pilot frequency sequence is used as a pilot frequency sequence x of a compressed OFDM systemp；
Step two, data sequence xdAfter constellation point mapping is carried out, serial/parallel conversion is carried out on the mapping result to obtain a serial/parallel converted result;
wherein, the data sequence xdHas a length of Nd；
Pilot sequence x according to comb pilot patternpInserting the result after serial/parallel conversion, namely uniformly distributing the pilot symbols of the comb-shaped pilot sequence in the result after serial/parallel conversion in an alternate-zero way to obtain a signal x containing the comb-shaped pilot, and performing N-IDFT conversion on the signal x to obtain an OFDM signal x after N-IDFT conversionOFDM；
Step three, the OFDM signal x after the N-IDFT conversionOFDMBy cutting off the filter phiNIntercepting the front N/2 point signal to obtain a compressed OFDM symbol xp1,comb；
OFDM signal x after N-IDFT conversionOFDMRear L ofCPPoint as a compressed OFDM symbol xp1,combThe OFDM signal s inserted with the cyclic prefix CP is obtainedp1,comb；
Then, the OFDM signal s after the cyclic prefix CP is inserted is processedp1,combAfter parallel/serial conversion, obtaining a compressed OFDM symbol S to be sentPA plurality of compressed OFDM symbols form a data frame and are transmitted;
at the receiving end
Step four, receiving signalsSynchronizing to obtain synchronized received signal RPAnd from RPIn order to obtain pilot symbol yP；
Step five, according to the obtained pilot frequency symbol yPPerforming channel estimation to obtain channel impulse response h;
and step six, according to the obtained channel impulse response h, carrying out equalization and extrapolation reconstruction on the received data part, and then carrying out subsequent detection on a signal obtained by extrapolation reconstruction so as to recover the data sent by the sending end.
According to another aspect of the present invention, a method for designing a pilot sequence in a truncated and extrapolated reconstructed multi-carrier signal includes the following steps:
at the transmitting end
after the serial/parallel conversion and N-IDFT conversion are carried out on the block pilot frequency sequence after the completion in turn, the block pilot frequency sequence x after the N-IDFT conversion is carried outp1,blockThrough a cut-off filter phiNObtaining compressed OFDM block pilot frequency symbol sp1,block；
And converting the N-IDFT transformed block pilot frequency sequence xp1,blockRear L ofCPDotted as compressed OFDM block pilot symbols sp1,blockThe cyclic prefix CP is inserted into the compressed OFDM block pilot symbols to obtain the block pilot symbols after the cyclic prefix CP is inserted;
performing parallel/serial conversion on the block pilot symbols after the cyclic prefix CP is inserted to obtain the block pilot symbols after the parallel/serial conversion;
Then the initial data symbol xd1,blockRear L ofCPPoint as pressureReduced OFDM data symbols sd1,blockThe cyclic prefix CP is inserted into the compressed OFDM data symbol sd1,blockObtaining a data symbol inserted with a cyclic prefix CP;
performing parallel/serial conversion on the data symbols with the cyclic prefix CP inserted therein to obtain compressed OFDM data symbols to be sent, wherein a plurality of compressed OFDM data symbols to be sent form data frames to be sent;
at the receiving end
and 6, according to the channel impulse response h obtained in the step 5, equalizing and extrapolating reconstruction are carried out on the received data part, and then subsequent detection is carried out on the signal obtained by the extrapolating reconstruction, so that the data sent by the sending end is recovered.
The invention has the beneficial effects that: the invention provides a design method for truncating and extrapolating a pilot frequency sequence in a reconstructed multi-carrier signal, which aims at the problem that self-interference introduced by a compressed OFDM transmission method influences the accuracy of pilot frequency-assisted channel estimation, and reduces the distortion degree of compressed pilot frequency and improves the accuracy of channel estimation by designing a pilot frequency sequence with null points.
Drawings
FIG. 1 is a schematic diagram of an 8-point uncompressed all-1 pilot spectrum;
1-8 on the abscissa in fig. 1 represents the center frequency of each subcarrier, and when uncompressed, the subcarriers are orthogonal, that is, the sampling point on each center frequency is the amplitude of the current subcarrier, and there is no interference of other subcarriers;
FIG. 2 is a diagram of an 8-point unscheduled compressed pilot spectrum;
the two dashed lines in fig. 2 represent the magnitude of the self-interference contained at the first/four sub-carrier sample points of the compressed pilot, respectively. As can be seen from the first dashed line, the self-interference mainly includes the interference of the second subcarrier adjacent to the right side and the interference of other subcarriers with even numbers, and the amplitude of the self-interference at the first compressed pilot subcarrier can be represented as:
wherein, IkRepresenting the interference on the k-th subcarrier, N representing the number of pilot subcarriers, 2t traversing even subcarriers in the N subcarriers, and sinc function represented as
| t | represents taking the absolute value of t.
Similarly, the second dotted line receives strong interference from adjacent pilot subcarriers on both sides and interference from other odd subcarriers at the same time due to being in the middle position, and then the self-interference amplitude at the fourth compressed pilot subcarrier can be expressed as:
where 2t-1 traverses odd subcarriers within the N subcarriers.
FIG. 3 is a schematic diagram of an 8-point zero-inserted pilot frequency spectrum designed by the present invention;
FIG. 4 is a schematic diagram of 8-point zero-inserted compressed pilot frequency spectrum designed by the present invention;
corresponding to fig. 2, the positions of two dotted lines in fig. 3 represent the amplitude of self-interference included at the first/four sub-carrier sampling points of the zero-inserted pilot, respectively, and fig. 4 is the amplitude of self-interference included at the first/four sub-carrier sampling points after the pilot in fig. 3 is truncated and compressed. As shown in fig. 4, when the compressed OFDM signal is used for channel estimation, only the pilot information at the odd number of subcarriers (i.e. at the 1 st, 3 rd, 5 th, and 7 th subcarriers in the figure) is needed; although self-interference still exists at the 4 th subcarrier, the result of channel estimation is not affected, because the channel information at the 4 th subcarrier can be obtained by interpolation according to the channel information of the odd-numbered subcarriers;
FIG. 5 is a flow chart of the transceiving end of the truncated and extrapolated reconstructed multicarrier system with comb pilot inserted;
FIG. 6 is a diagram illustrating insertion of comb pilots in the present invention;
as can be seen from fig. 6, for a system using comb-shaped pilot, a pilot sequence is directly inserted into a single symbol, and zeros are added before and after the insertion of the comb-shaped pilot, so as to cancel the influence of non-orthogonal data on the pilot;
FIG. 7 is a flow chart of the transceiving end of the truncated and extrapolated reconstructed multicarrier system with block pilot inserted;
FIG. 8 is a diagram illustrating the insertion of a block pilot in the present invention;
as can be seen from fig. 8, the inserted block pilot symbols are zeroed out at intervals, so there is no self-interference at each subcarrier frequency, while there is still self-interference in the data part because the zeroed out operation is not performed.
Detailed Description
First embodiment this embodiment will be described with reference to fig. 5. The method for designing a pilot sequence in a truncated and extrapolated reconstructed multi-carrier signal according to this embodiment specifically includes the following steps:
at the transmitting end
Step one, generating a group of N-lengthpThe generated comb-shaped pilot frequency sequence is used as a pilot frequency sequence x of a compressed OFDM systemp；
Step two, data sequence xdAfter constellation point mapping is carried out, serial/parallel conversion (S/P conversion) is carried out on the mapping result to obtain a result after the serial/parallel conversion;
wherein, the data sequence xdHas a length of Nd；
Pilot sequence x according to comb pilot patternpInsert intoIn the result after serial/parallel conversion, the pilot frequency symbols of the comb-shaped pilot frequency sequence are uniformly distributed in the result after serial/parallel conversion in an interval of zero to obtain a signal x containing the comb-shaped pilot frequency, and the signal x is subjected to N-IDFT (N-point inverse discrete Fourier transform) to obtain an OFDM signal x after N-IDFT conversionOFDM；
Wherein the IDFT process can be expressed as
Step three, the OFDM signal x after the N-IDFT conversionOFDMBy cutting off the filter phiNIntercepting the front N/2 point signal to obtain a compressed OFDM symbol xp1,comb；
OFDM signal x after N-IDFT conversionOFDMRear L ofCPPoint as a compressed OFDM symbol xp1,combThe OFDM signal s inserted with the cyclic prefix CP is obtainedp1,comb；
Then, the OFDM signal s after the cyclic prefix CP is inserted is processedp1,combAfter parallel/serial conversion (P/S conversion), obtaining a compressed OFDM symbol S to be transmittedPA plurality of (more than or equal to 2) compressed OFDM symbols form a data frame and are transmitted;
at the receiving end
Step four, synchronizing the received signals to obtain synchronized received signals RPAnd from RPIn order to obtain pilot symbol yP；
Step five, according to the obtained pilot frequency symbol yPPerforming channel estimation to obtain channel impulse response h;
it should be noted that for different compressed transmission communication scenarios, different channel estimation methods should be employed. For example, for a large-scale millimeter wave communication scene, most of the conventional parameter estimation methods are not applicable, and channel estimation based on compressed sensing or deep learning is required; for the channel environment of a single antenna or a small-scale antenna, the traditional LS, MMSE, Kalman filtering channel estimation method and the like can be adopted;
and step six, according to the obtained channel impulse response h, carrying out equalization and extrapolation reconstruction on the received data part, and then carrying out subsequent detection on a signal obtained by extrapolation reconstruction so as to recover the data sent by the sending end.
The second embodiment is as follows: the present embodiment is different from the first embodiment in that the length of the comb-shaped pilot-containing signal x is N ═ Np+Nd。
The third concrete implementation mode: the difference between this embodiment and the second embodiment is that, in the first step, a group of the length N is generatedpThe comb pilot sequence of (2) is a PN sequence, a full sequence, or a random sequence.
Aiming at a multipath channel, particularly in a multi-antenna system, a PN sequence with good correlation is adopted as a pilot frequency sequence; the PN sequence satisfies the following conditions:
wherein p ismFor cyclically shifting the PN sequence by m bits, pnFor the PN sequence after cyclic shift by n bits,
represents pnConjugation of (1).
The m sequence, Gold sequence, Gray sequence, etc. can be directly generated by a generator, and the amplitude APN∈{-1,+1}。
The full sequence is
The random sequence is xp＝randi(1,Np)。
The fourth concrete implementation mode: this embodiment will be described with reference to fig. 6. The difference between this embodiment and the third embodiment is that, in the signal x containing comb-shaped pilots, the pilot symbol interval is smaller than the coherence bandwidth of the channel.
The coherent bandwidth is determined by the time delay of the multipath channel, and refers to a frequency range in which any two frequency components in the multipath channel have strong amplitude correlation.
The embodiment ensures compression transmission and simultaneously inhibits the self-interference of the pilot signal generated by compression. Although the pilot frequency is subjected to the zero setting operation, the time frequency resource occupied by the pilot frequency sequence is not increased. Although the number of effective points is reduced relative to the pilot sequence that is not set to zero, pilot distortion due to self-interference is suppressed. Meanwhile, the zero setting operation does not need the processes of complex multiplication and the like, so the computational complexity of the transmitting end is not improved.
The fifth concrete implementation mode: the present embodiment is different from the fourth embodiment in that the OFDM signal x after N-IDFT conversion is usedOFDMBy cutting off the filter phiNIntercepting the front N/2 point signal to obtain a compressed OFDM symbol xp1,comb(ii) a The specific process comprises the following steps:
step three one, generating a cut-off filter phiN：
Step three and two, the OFDM signal x after the N-IDFT transformation is carried out on the time domainOFDMPerforming truncation processing to obtain a compressed OFDM symbol xp1,comb：
xp1,comb＝xOFDM·ΦN。
It should be noted that the insertion period f of the comb pilotfAnd channel maximum delay spread sigmamaxIn a relationship of
ff≤1/σmax
The sixth specific implementation mode: the difference between this embodiment and the fifth embodiment is that the pilot symbol y is obtainedPThe specific process comprises the following steps:
for the synchronized received signal RPPerforming N-DFT (N-point discrete Fourier transform) to obtain a result after the N-DFT; and acquiring the comb-shaped pilot frequency band on the frequency domain of the result after the N-DFT conversion.
Wherein the DFT process can be expressed as
Seventh embodiment, this embodiment will be described with reference to fig. 7 and 8. The method for designing a pilot sequence in a truncated and extrapolated reconstructed multi-carrier signal according to this embodiment specifically includes the following steps:
at the transmitting end
after the series/parallel conversion (S/P conversion) and the N-IDFT conversion (N-point inverse discrete Fourier transform) are carried out on the complemented block pilot sequence in sequence, the block pilot sequence x after the N-IDFT conversion is carried outp1,blockThrough a cut-off filter phiNObtaining compressed OFDM block pilot frequency symbol sp1,block；
And converting the N-IDFT transformed block pilot frequency sequence xp1,blockRear L ofCPDotted as compressed OFDM block pilot symbols sp1,blockThe cyclic prefix CP is inserted into the compressed OFDM block pilot symbols to obtain the block pilot symbols after the cyclic prefix CP is inserted;
performing parallel/serial conversion (P/S conversion) on the block pilot symbols after the cyclic prefix CP is inserted to obtain block pilot symbols after the parallel/serial conversion;
Then the initial data symbol xd1,blockRear L ofCPDotted as compressed OFDM data symbol sd1,blockThe cyclic prefix CP is inserted into the compressed OFDM data symbol sd1,blockObtaining a data symbol inserted with a cyclic prefix CP;
performing parallel/serial conversion on the data symbols after the cyclic prefix CP is inserted to obtain compressed OFDM data symbols to be sent, wherein a plurality of (more than or equal to 2) compressed OFDM data symbols to be sent form a data frame to be sent;
at the receiving end
If the insertion mode of the block pilot frequency is adopted, the block pilot frequency time interval in the received signal is periodically intercepted on the time domain, and the insertion period of the known pilot frequency symbol is Tt(ii) a For RPAfter finding the position of the first pilot block, every TtThe obtained complete symbol is the pilot symbol yP；
and 6, according to the channel impulse response h obtained in the step 5, equalizing and extrapolating reconstruction are carried out on the received data part, and then subsequent detection is carried out on the signal obtained by the extrapolating reconstruction, so that the data sent by the sending end is recovered.
The embodiment is designed based on the process of a sending end, different extraction means are adopted for different pilot frequency insertion modes under the non-orthogonal environment of compression transmission, and the extracted pilot frequency can be regarded as the approximately orthogonal relation; approximate orthogonality may enable approximate cancellation of self-interference, enabling more accurate channel estimation with less pilot.
In the invention, in the pilot frequency sequence: n is a radical ofp＝N,N d0; in the data sequence: n is a radical ofp＝0,Nd＝N。
The specific implementation mode is eight: the seventh embodiment is different from the seventh embodiment in that a group of block-shaped pilot sequences with the length of N/2 is generated in the step 1, and the pilot sequences are PN sequences, full sequences or random sequences.
Aiming at a multipath channel, particularly in a multi-antenna system, a PN sequence with good correlation is adopted as a pilot frequency sequence; the PN sequence satisfies the following conditions:
wherein p ismFor cyclically shifting the PN sequence by m bits, pnFor the PN sequence after cyclic shift by n bits,
represents pnConjugation of (1).
The m sequence, Gold sequence, Gray sequence, etc. can be directly generated by a generator, and the amplitude APN∈{-1,+1}。
The full sequence is
The random sequence is xp＝randi(1,Np)。
The specific implementation method nine: the eighth embodiment is different from the eighth embodiment in that the cut filter ΦNIn the form of:
pilot sequence xp1,blockThrough a cut-off filter phiN：
sp1,block＝xp1,block·ΦN
Wherein s isp1,blockCompressing OFDM block pilot symbols;
initial data symbol xd1,blockThrough a cut-off filter phiN：
sd1,block＝xd1,block·ΦN
Wherein s isd1,blockIs a compressed OFDM data symbol.
The detailed implementation mode is ten: this embodiment is different from the ninth embodiment in that the period T istAnd the maximum Doppler shift f of the channeldThe relationship of (1) is: t ist≤1/fd。
The concrete implementation mode eleven: this embodiment is quite different from the embodiment in that the period T istIs an integer multiple of T, which represents the period duration of one OFDM data symbol.
The invention discloses a design method of a transmitting end for truncating and extrapolating reconstructed multi-carrier signals by inserting different pilot frequencies while ensuring compression transmission. The block pilot frequency can accurately estimate the channel information on each subcarrier in the bandwidth and is suitable for a frequency selective channel; the comb-shaped pilot frequency can estimate the fast time-varying channel more effectively, and has certain practical application significance.
The above-described calculation examples of the present invention are merely to explain the calculation model and the calculation flow of the present invention in detail, and are not intended to limit the embodiments of the present invention. It will be apparent to those skilled in the art that other variations and modifications of the present invention can be made based on the above description, and it is not intended to be exhaustive or to limit the invention to the precise form disclosed, and all such modifications and variations are possible and contemplated as falling within the scope of the invention.
Claims (11)
1. A method for designing a pilot sequence in a truncated and extrapolated reconstructed multi-carrier signal, the method comprising:
at the transmitting end
Step one, generating a group of N-lengthpThe generated comb-shaped pilot frequency sequence is used as a pilot frequency sequence x of a compressed OFDM systemp；
Step two, data sequence xdAfter constellation point mapping is carried out, serial/parallel conversion is carried out on the mapping result to obtain a serial/parallel converted result;
wherein, the data sequence xdHas a length of Nd；
Pilot sequence x according to comb pilot patternpInserting the result after serial/parallel conversion, namely uniformly distributing the pilot symbols of the comb-shaped pilot sequence in the result after serial/parallel conversion in an alternate-zero way to obtain a signal x containing the comb-shaped pilot, and performing N-IDFT conversion on the signal x to obtain an OFDM signal x after N-IDFT conversionOFDM；
Step three, the OFDM signal x after the N-IDFT conversionOFDMBy cutting off the filter phiNIntercepting the front N/2 point signal to obtain a compressed OFDM symbol xp1,comb；
OFDM signal x after N-IDFT conversionOFDMRear L ofCPPoint as a compressed OFDM symbol xp1,combThe OFDM signal s inserted with the cyclic prefix CP is obtainedp1,comb；
Then, the OFDM signal s after the cyclic prefix CP is inserted is processedp1,combAfter parallel/serial conversion, obtaining a compressed OFDM symbol S to be sentPA plurality of compressed OFDM symbols form a data frame and are transmitted;
at the receiving end
Step four, synchronizing the received signals to obtain synchronized received signals RPAnd from RPIn order to obtain pilot symbol yP；
Step five, according to the obtained pilot frequency symbol yPPerforming channel estimation to obtain channel impulse response h;
and step six, according to the obtained channel impulse response h, carrying out equalization and extrapolation reconstruction on the received data part, and then carrying out subsequent detection on a signal obtained by extrapolation reconstruction so as to recover the data sent by the sending end.
2. The method as claimed in claim 1, wherein the length of the signal x containing comb-shaped pilots is N-Np+Nd。
3. Truncation and extrapolation as claimed in claim 2 for reconstructing a pilot sequence in a multi-carrier signalThe design method is characterized in that a group of N lengths is generated in the first steppThe comb pilot sequence of (2) is a PN sequence, a full sequence, or a random sequence.
4. The method as claimed in claim 3, wherein the pilot symbol spacing in the comb-shaped pilot-containing signal x is smaller than the coherence bandwidth of the channel.
5. The method of claim 4, wherein the N-IDFT transformed OFDM signal x is used as a basis for the design of pilot sequences in the truncated and extrapolated reconstructed multi-carrier signalOFDMBy cutting off the filter phiNIntercepting the front N/2 point signal to obtain a compressed OFDM symbol xp1,comb(ii) a The specific process comprises the following steps:
step three one, generating a cut-off filter phiN：
Step three and two, the OFDM signal x after the N-IDFT transformation is carried out on the time domainOFDMPerforming truncation processing to obtain a compressed OFDM symbol xp1,comb：
xp1,comb＝xOFDM·ΦN。
6. The method of claim 5, wherein the pilot symbol y is obtained by truncating and extrapolating the pilot sequence in the reconstructed multi-carrier signalPThe specific process comprises the following steps:
for the synchronized received signal RPPerforming N-DFT conversion to obtain a result after the N-DFT conversion; and acquiring the comb-shaped pilot frequency band on the frequency domain of the result after the N-DFT conversion.
7. A method for designing a pilot sequence in a truncated and extrapolated reconstructed multi-carrier signal, the method comprising:
at the transmitting end
Step 1, generating a group of block pilot sequences with the length of N/2, and carrying out alternate point zero insertion operation on the generated block pilot sequences to make the length of the block pilot sequences complete to be N;
after the serial/parallel conversion and N-IDFT conversion are carried out on the block pilot frequency sequence after the completion in turn, the block pilot frequency sequence x after the N-IDFT conversion is carried outp1,blockThrough a cut-off filter phiNObtaining compressed OFDM block pilot frequency symbol sp1,block；
And converting the N-IDFT transformed block pilot frequency sequence xp1,blockRear L ofCPDotted as compressed OFDM block pilot symbols sp1,blockThe cyclic prefix CP is inserted into the compressed OFDM block pilot symbols to obtain the block pilot symbols after the cyclic prefix CP is inserted;
performing parallel/serial conversion on the block pilot symbols after the cyclic prefix CP is inserted to obtain the block pilot symbols after the parallel/serial conversion;
step 2, aiming at source bit data xdAfter constellation point mapping, S/P conversion and N-IDFT, an initial data symbol x is obtainedd1,block(ii) a And passes the initial data symbols through a truncation filter phiNObtaining a compressed OFDM data symbol sd1,block；
Then the initial data symbol xd1,blockRear L ofCPDotted as compressed OFDM data symbol sd1,blockThe cyclic prefix CP is inserted into the compressed OFDM data symbol sd1,blockObtaining a data symbol inserted with a cyclic prefix CP;
performing parallel/serial conversion on the data symbols with the cyclic prefix CP inserted therein to obtain compressed OFDM data symbols to be sent, wherein a plurality of compressed OFDM data symbols to be sent form data frames to be sent;
step 3, converting the block pilot frequency symbol obtained in step 1 with period TtInserting the data frame to be sent obtained in the step 2;
at the receiving end
Step 4, receivingThe signals are synchronized to obtain a synchronized receiving signal RPAnd from RPIn order to obtain pilot symbol yP；
Step 5, the pilot frequency symbol y obtained according to the step 4PPerforming channel estimation to obtain channel impulse response h;
and 6, according to the channel impulse response h obtained in the step 5, equalizing and extrapolating reconstruction are carried out on the received data part, and then subsequent detection is carried out on the signal obtained by the extrapolating reconstruction, so that the data sent by the sending end is recovered.
8. The method as claimed in claim 7, wherein the step 1 generates a set of block-shaped pilot sequences with length N/2, and the pilot sequences are PN sequences, full sequences or random sequences.
9. The method of claim 8, wherein the truncation filter Φ is a filter that truncates and extrapolates the pilot sequence in the reconstructed multi-carrier signalNIn the form of:
pilot sequence xp1,blockThrough a cut-off filter phiN：
sp1,block＝xp1,block·ΦN
Wherein s isp1,blockCompressing OFDM block pilot symbols;
initial data symbol xd1,blockThrough a cut-off filter phiN：
sd1,block＝xd1,block·ΦN
Wherein s isd1,blockIs a compressed OFDM data symbol.
10. Truncation and extrapolation as claimed in claim 9 for reconstructing a pilot sequence in a multi-carrier signalMethod of designing, characterized in that said period T istAnd the maximum Doppler shift f of the channeldThe relationship of (1) is: t ist≤1/fd。
11. The method of claim 10, wherein the period T is a period of time TtIs an integer multiple of T, which represents the period duration of one OFDM data symbol.
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