CN110912849B - Multi-carrier method and system based on cyclic prefix - Google Patents

Multi-carrier method and system based on cyclic prefix Download PDF

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CN110912849B
CN110912849B CN201911147888.0A CN201911147888A CN110912849B CN 110912849 B CN110912849 B CN 110912849B CN 201911147888 A CN201911147888 A CN 201911147888A CN 110912849 B CN110912849 B CN 110912849B
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orthogonal
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branch
cyclic prefix
time domain
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CN110912849A (en
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江涛
孔德进
郑行
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Huazhong University of Science and Technology
Wuhan Textile University
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Huazhong University of Science and Technology
Wuhan Textile University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators

Abstract

The invention discloses a multicarrier method and system based on cyclic prefix, belonging to the technical field of communication, comprising the following steps: synchronously performing inverse discrete Fourier transform on all subcarrier sending symbols in each orthogonal branch to obtain a time domain sending signal; synchronously delaying the time domain sending signals transmitted on each orthogonal branch in sequence by rT and multiplying the time domain sending signals by corresponding phase factors ej2πrp/RAcquiring time domain orthogonal signals on each orthogonal branch; synchronously superposing the time domain orthogonal signals acquired from each orthogonal branch, and then performing cyclic prefix processing to acquire a transmitting signal of a transmitting end; wherein r is an integer set [0, K ]](ii) a T is a symbol period; k is more than or equal to the number R of the orthogonal branches; p is the serial number of the quadrature branch. Each sending symbol transmitted by the orthogonal branch circuit provided by the invention is repeatedly delayed for K times, only a section of CP needs to be inserted at every KM sampling points, and the maximum number of the orthogonal branch circuits is not more than a preset delay coefficient, so that the CP expense of a multi-carrier communication system is reduced, and the system error rate is not increased.

Description

Multi-carrier method and system based on cyclic prefix
Technical Field
The present invention belongs to the field of communication technologies, and in particular, to a cyclic prefix-based multi-carrier method and system.
Background
Multicarrier communication techniques, and in particular Orthogonal Frequency Division Multiplexing (OFDM) communication techniques, have been widely used in wireless communications. A significant drawback of OFDM techniques is that each OFDM symbol requires the insertion of a Cyclic Prefix (CP) to effectively combat the effects of multipath fading channels, however, the insertion of a CP in each OFDM symbol significantly reduces the energy efficiency and spectral efficiency of the multi-carrier communication system. At present, methods for reducing CP overhead of multi-carrier communication mainly include two types:
(1) iterative methods, "p.torres and a.gusmao," Iterative receiver Technology for reduced-CP, reduced-PMEPR OFDM transmission, "IEEE temporal Technology Conference, pp.1981-1985, May 2007," disclosing that direct reduction of CP length introduces inter-symbol interference and inter-carrier interference. The method not only has higher complexity, but also can not completely eliminate the interference between carriers and the interference between symbols, and can cause the bit error rate of the multi-carrier communication system to be increased when a debugging mode with high code rate is adopted.
(2) The filter method, "p.siohan, c.siclet and n.lacaile," Analysis and design of OQAM-OFDM systems based on filter bank, "IEEE Transactions on Signal Processing, vol.50, No.5, pp.1170-1183, may.2002" discloses that the transmitted symbols of each subcarrier of a multicarrier communication system pass through a prototype filter having time-frequency two-dimensional focusing, and the multicarrier communication system cannot insert a cyclic prefix due to the adoption of a non-rectangular window filter. However, the multi-carrier communication system cannot effectively combat a multi-path fading channel, and under the condition that the bandwidth of the multi-carrier communication system is large, the multi-carrier communication system has large interference and poor error rate.
(3) The Precoded OFDM, "X. -G.Xia," Precoded and vector OFDM robust to channel spectral nulls and with reduced cyclic prefix length in single transmit antenna systems, "IEEE Transactions on Communications, vol.49, No.8, pp.1363-1374, and aug.2001" discloses that a multicarrier communication system precodes a plurality of symbols, and intercepts a tail of the symbols to form a cyclic prefix, and transmits the cyclic prefix through transmitting antennas, thereby simplifying the receiver complexity through channel diagonalization at the receiving end. The multi-carrier communication system can greatly reduce CP expense of OFDM technology without influencing error rate performance. However, at the receiving end of the multi-carrier communication system, although the channel diagonalization process can reduce the complexity, the complexity of the receiver is still relatively large.
In summary, the drawbacks of the current method for reducing CP overhead in a multi-carrier system include: the error rate of the multi-carrier communication system is increased or the complexity is large.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a multicarrier method and a multicarrier system based on cyclic prefix, and aims to solve the problem that the system error rate is increased in the conventional method for reducing the CP overhead of a multicarrier communication system.
To achieve the above object, in one aspect, the present invention provides a cyclic prefix-based multi-carrier method, including:
(1) synchronously performing inverse discrete Fourier transform on all subcarrier sending symbols in each orthogonal branch to obtain a time domain sending signal;
(2) synchronously delaying the time domain sending signals transmitted on each orthogonal branch in sequence by rT and multiplying the time domain sending signals by corresponding phase factors ej2πrp/RAcquiring time domain orthogonal signals on each orthogonal branch;
(3) synchronously superposing the time domain orthogonal signals acquired from each orthogonal branch, and then performing cyclic prefix processing to acquire a transmitting signal of a transmitting end;
wherein r is an integer set [0, K ]; k is a preset delay coefficient; t is a symbol period; k is more than or equal to the number R of the orthogonal branches; p is the serial number of the quadrature branch.
Preferably, the preset delay coefficient K is equal to the number R of the orthogonal branches;
preferably, the transmission signal is converted into a reception signal at the receiving end, and the demodulation process of the reception signal is as follows:
a. removing a cyclic prefix in a received signal;
b. performing discrete Fourier transform on the received signal without the cyclic prefix to obtain a frequency domain received signal without the cyclic prefix;
c. equalizing the channel of the frequency domain received signal without the cyclic prefix;
d. judging whether the serial number of the orthogonal branch after channel equalization is 0, if so, the equalized signal at the position of the mR after equalization is the sending symbol of the 0 th orthogonal branch; otherwise, go to step e;
e. extracting the balanced signal with the serial number mR + p as a sending signal of the p-th orthogonal branch;
f. performing inverse discrete Fourier transform on the acquired transmission signal to acquire a time domain transmission signal;
g. segmenting a time domain transmission signal by taking one symbol period as a unit;
h. the segmented transmission signals are all multiplied by a phase factor ej2πrp/R；
i. For multiplication by a phase factor ej2πrp/RThe transmitted signal of (2) is subjected to discrete fourier transform to obtain symbol demodulation of each orthogonal branch.
In another aspect, the present invention provides a cyclic prefix-based multi-carrier system, including: the system comprises an orthogonal branch, a carrier loader, a first Fourier inverse transformer, a signal delayer and a cyclic prefix processor;
the input end of the orthogonal branch is connected with a carrier loader; the output end of the orthogonal branch is connected with the first Fourier inverse transformer, the signal delayer and the cyclic prefix processor in sequence;
the orthogonal branch is used for synchronously transmitting the sending symbol; the carrier loader is used for loading the sending symbols on the orthogonal branch; the first Fourier inverse transformer is used for carrying out inverse discrete Fourier transform on the transmitting symbols transmitted in each orthogonal branch to obtain a time domain transmitting signal; the signal delayer is used for delaying the time domain transmission signal by rT in sequence and multiplying the time domain transmission signal by a corresponding phase factor ej2 πrp/RAcquiring time domain orthogonal signals on each orthogonal branch; the cyclic prefix processor is used for performing cyclic prefix processing after the time domain orthogonal signals acquired on each orthogonal branch are superposed to acquire transmitting signals;
wherein r is an integer set [0, K ]; k is a preset delay coefficient; t is a symbol period; k is more than or equal to the number R of the orthogonal branches; p is the serial number of the quadrature branch.
Preferably, K is equal to the number R of orthogonal branches;
preferably, the cyclic prefix based multi-carrier system further comprises: the device comprises a receiver, a cyclic prefix removing processor, a first Fourier transformer, a channel equalizer, an extraction module, a second Fourier inverse transformer, a phase modulator and a second Fourier transformer which are connected in sequence;
the de-cyclic prefix processor is used for removing the cyclic prefix in the transmitting signal; the first Fourier transformer is used for removingPerforming discrete Fourier transform on the transmitting signals except the cyclic prefix, and converting the transmitting signals into frequency domain signals from time domain signals; the channel equalizer is used for equalizing the channel of the frequency domain transmitting signal without the cyclic prefix; the extraction module is used for judging whether the serial number of the orthogonal branch is 0 or not, and if so, the equalized signal at the position of the mR after equalization is extracted is the sending symbol of the 0 th orthogonal branch; otherwise, extracting the equalization signal with the serial number mR + p as the transmission signal of the p-th orthogonal branch; the second inverse Fourier transformer is used for performing inverse discrete Fourier transform on the transmission signal of the p-th orthogonal branch to obtain a time-domain transmission signal; the phase modulator is used for segmenting the time domain transmission signal by taking one symbol period as a unit and multiplying the time domain transmission signal by a phase factor ej2πrp/R(ii) a A second Fourier transformer for multiplying by a phase factor ej2πrp/RThe transmitted signal of (2) is subjected to discrete fourier transform to obtain symbol demodulation of each orthogonal branch.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
(1) the multi-carrier method and system based on cyclic prefix provided by the invention has the advantages that the sending end is provided with a plurality of orthogonal branches, can transmit a plurality of symbols simultaneously, the maximum number of orthogonal branches is not more than a preset delay coefficient K, obtain repeated symbols, otherwise, the multi-carrier communication system is easy to generate interference, and the repeated symbols of each orthogonal branch in the multi-carrier system are respectively multiplied by phase factors after discrete Fourier transform, the phase factors of different orthogonal branches are orthogonal to ensure the interference-free transmission of the symbols, meanwhile, assuming that R orthogonal branches are provided, each orthogonal branch comprises M subcarriers, a section of CP is inserted into every M sampling points in the traditional OFDM, the invention adopts the orthogonal branch to transmit each transmitting symbol repeatedly and delays for K times, only a section of CP needs to be inserted every KM sampling points, therefore, the invention reduces the CP overhead of the multi-carrier communication system without increasing the system error rate.
(2) Because the receiving signals of the sending symbols of different orthogonal branches are separated on the time domain, signal extraction is needed for recovering the sending symbols on the orthogonal branches, and because the signals of different orthogonal branches are separated on the time domain, the sending symbols of different orthogonal branches can be independently demodulated without joint solution, thereby reducing the complexity; after signal extraction, symbol demodulation can be realized by performing DFT (discrete fourier transform), multiplication by a phase factor and IDFT (inverse discrete fourier transform), and since IDFT can be realized by FFT, the implementation complexity is low, so the receiving end of the multi-carrier system has low implementation complexity.
(3) The invention adopts the preset delay coefficient K equal to the number R of the orthogonal branches, and the main reason is that when the preset delay coefficient K is less than the number R of the orthogonal branches, the multi-carrier communication system is easy to generate interference and cannot demodulate a sending symbol.
Drawings
Fig. 1 is a cyclic prefix-based multi-carrier method provided by an embodiment;
fig. 2 is a schematic diagram of a demodulation process based on the transmission signal of fig. 1 according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In one aspect, the present invention provides a cyclic prefix-based multi-carrier method, including:
(1) synchronously performing inverse discrete Fourier transform on all subcarrier sending symbols in each orthogonal branch to obtain a time domain sending signal;
presetting M sub-carriers corresponding to each orthogonal branch, and loading a sending symbol x on each orthogonal branch by the mth sub-carrierm,pSending a symbol xm,pGenerating a transmission signal by M-point IDFT (inverse discrete fourier transform); wherein m is the serial number of the subcarrier; p is the serial number of the orthogonal branch; m, m and p are integers of 0 or more;
(2) synchronously delaying the time domain sending signals transmitted on each orthogonal branch in sequence by rT and multiplying the time domain sending signals by corresponding phase factors ej2πrp/RAcquiring time domain orthogonal signals on each orthogonal branch;
a time domain transmission signal on a certain orthogonal branch passes through 0, MT in sequences，2MTs，......，KMTsDelayed and correspondingly multiplied by a phase factor ej2πrp/RWherein T is MTs，TsFor the sampling interval, r is the set of integers [0, K](ii) a K is a preset delay coefficient; t is a symbol period; k is more than or equal to the number R of the orthogonal branches;
(3) and synchronously superposing the time domain orthogonal signals acquired from each orthogonal branch, and then performing cyclic prefix processing to acquire the transmitting signals.
And overlapping the delayed time domain orthogonal signals to form an extended time domain orthogonal signal, intercepting a section of signal at the tail part of the extended time domain orthogonal signal, inserting the section of signal into the initial position of the extended time domain orthogonal signal to form a cyclic prefix, and acquiring a transmitting signal and transmitting the transmitting signal through a transmitting antenna.
Preferably, the preset delay coefficient K is equal to the number R of the orthogonal branches;
preferably, the transmission signal is converted into a reception signal at the receiving end, and the demodulation process of the reception signal is as follows:
a. removing a cyclic prefix in a received signal;
b. performing KM point discrete Fourier transform on the received signal without the cyclic prefix to obtain a frequency domain received signal without the cyclic prefix;
c. equalizing the channel of the frequency domain transmitting signal without the cyclic prefix;
d. judging whether the serial number of the orthogonal branch after channel equalization is 0, if so, the equalized signal at the position of the mR after equalization is the sending symbol of the 0 th orthogonal branch; otherwise, go to step e;
e. extracting the balanced signal with the serial number mR + p as a sending signal of the p-th orthogonal branch;
f. d, performing inverse discrete Fourier transform on the transmission signal obtained in the step e to obtain a time domain transmission signal;
g. segmenting a time domain transmission signal by taking one symbol period as a unit;
h. the segmented transmission signals are all multiplied by a phase factor ej2πrp/R；
i. For multiplication by a phase factor ej2πrp/RThe transmitted signal of (2) is subjected to discrete fourier transform to obtain symbol demodulation of each orthogonal branch.
In another aspect, the present invention provides a cyclic prefix-based multi-carrier system, including: the system comprises an orthogonal branch, a carrier loader, a first Fourier inverse transformer, a signal delayer and a cyclic prefix processor;
each orthogonal branch is connected with a carrier loader; the output end of the orthogonal branch is connected with the first Fourier inverse transformer, the signal delayer and the cyclic prefix processor in sequence;
the orthogonal branch is used for synchronously transmitting the sending symbol; the carrier loader is used for loading the sending symbols on the orthogonal branch; the first Fourier inverse transformer is used for carrying out inverse discrete Fourier transform on the transmitting symbols transmitted in each branch to obtain time-domain transmitting signals; the signal delayer is used for delaying the time domain transmission signal by rT in sequence and multiplying the time domain transmission signal by a corresponding phase factor ej2πrp/RAcquiring time domain orthogonal signals on each orthogonal branch; the cyclic prefix processor is used for performing cyclic prefix processing after the time domain orthogonal signals acquired on each orthogonal branch are superposed to acquire transmitting signals;
wherein r is an integer set [0, K ]; k is a preset delay coefficient; t is a symbol period; k is more than or equal to the number R of the orthogonal branches; p is the serial number of the quadrature branch.
Preferably, K is equal to the number R of orthogonal branches;
preferably, the cyclic prefix based multi-carrier system further comprises: the device comprises a receiver, a cyclic prefix removing processor, a first Fourier transformer, a channel equalizer, an extraction module, a second Fourier inverse transformer, a phase modulator and a second Fourier transformer which are connected in sequence;
the receiver is used for receiving the transmitting signal and converting the transmitting signal into a receiving signal; the de-cyclic prefix processor is used for removing the cyclic prefix in the received signal; the first Fourier transformer is used for performing discrete Fourier transform on the received signal without the cyclic prefix and converting the received signal from a time domain signal to a frequency domain signal; the channel equalizer is used for equalizing a frequency domain received signal channel with the cyclic prefix removed; the extraction module is used for judging whether the serial number of the orthogonal branch is 0 or not, and if so, the equalized signal at the position of the mR after equalization is extracted is the sending symbol of the 0 th orthogonal branch; otherwise, extracting the equalization signal with the serial number mR + p as the transmission signal of the p-th orthogonal branch; the second inverse Fourier transformer is used for performing inverse discrete Fourier transform on the transmission signal of the p-th orthogonal branch to obtain a time-domain transmission signal; the phase modulator is used for segmenting the time domain transmission signal by taking one symbol period as a unit and multiplying the time domain transmission signal by a phase factor ej2πrp/R(ii) a A second Fourier transformer for multiplying by a phase factor ej2πrp/RThe transmitted signal of (2) is subjected to discrete fourier transform to obtain symbol demodulation of each orthogonal branch.
Examples
An embodiment provides a multi-carrier system with 2048 subcarriers, where the symbol mapping scheme adopts a 4QAM mapping scheme, the maximum number of repetitions R of each symbol is 2, and the number of maximum orthogonal branches is 2. Let the transmitted symbol be am,pWherein m is more than or equal to 0 and less than 2048 is the serial number of the subcarrier, and p is more than or equal to 0 and less than 2 is the serial number of the orthogonal branch.
As shown in fig. 1, the embodiment provides a cyclic prefix-based multi-carrier method, which specifically includes the following steps:
(1) the sending end carries out frequency domain symbol x on each orthogonal branchm,pGenerating time domain signal by 2048-point IDFT operation
Figure BDA0002282722150000081
N, m and p are integer numbers, n is more than or equal to 0 and less than 2048, and p is more than or equal to 0 and less than 2;
(2) for each orthogonal branch, respectively comparing the time domain signal s generated after IDFTp(n) delay rT, r ∈ [0,1 ]]T is the symbol period;
(3) multiplying the signals generated in step (2) by the corresponding phase factors, respectively, can be expressed as
Figure BDA0002282722150000082
(4) Intercepting a signal
Figure BDA0002282722150000083
Inserting a section of signal at the tail part into the initial position to form a cyclic prefix, and finally sending the cyclic prefix through a transmitting antenna;
as shown in fig. 2, the embodiment provides a demodulation process of a received signal, which specifically includes the following steps:
(5) at a receiving end, cutting off a cyclic prefix at the front part of a received signal;
(6) performing DFT on the signal obtained in the step (5), wherein the length of the DFT is 2048 times of that of the DFT, and then performing frequency domain channel equalization on the obtained signal to obtain r (n); for p equal to 0, the signal at the position of mR after frequency domain equalization is the transmission symbol of the recovered 0 th orthogonal branch
Figure BDA0002282722150000091
For p is more than or equal to 1, symbol demodulation is switched to the step (7) to the step (9);
(7) respectively extracting a signal aiming at the symbol of each orthogonal branch, and extracting a signal r (2m + p) at a serial number 2m + p for the p-th orthogonal branch, wherein other positions of the signal are 0, namely r (2m + q) is 0, and q is not equal to p;
(8) performing 4096-point IDFT on the signal obtained in the step (7) to obtain a signal
Figure BDA0002282722150000092
Where n is 0,1, …,4095, the signal is then segmented in units of one symbol period and, if the transmitted symbol of the p-th quadrature branch is to be recovered, multiplied by the phase factor e of the p-th quadrature branch-j2πrp/2. Signal
Figure BDA0002282722150000093
Multiplied by a phase factor e-j2π0p/2Of a signal
Figure BDA0002282722150000094
Multiplied by a phase factor e-j2πp/2；
(9) And (4) respectively carrying out 4096-point DFT on the signals obtained in the step (8), thereby realizing symbol demodulation of each orthogonal branch.
In summary, the sending end of the multi-carrier method and system based on cyclic prefix provided by the present invention has multiple orthogonal branches, can transmit a plurality of symbols simultaneously, the maximum number of orthogonal branches is not more than a preset delay coefficient K, obtain repeated symbols, otherwise, the multi-carrier communication system is easy to generate interference, and the repeated symbols of each orthogonal branch in the multi-carrier system are respectively multiplied by phase factors after discrete Fourier transform, the phase factors of different orthogonal branches are orthogonal to ensure the interference-free transmission of the symbols, meanwhile, assuming that R orthogonal branches are provided, each orthogonal branch comprises M subcarriers, a section of CP is inserted into every M sampling points in the traditional OFDM, the invention adopts the orthogonal branch to repeatedly delay each transmitting symbol for K times at the same time, only a section of CP is inserted at every KM sampling points, therefore, the invention reduces the CP overhead of the multi-carrier communication system without increasing the system error rate.
Because the receiving signals of the sending symbols of different orthogonal branches are separated on the time domain, signal extraction is needed for recovering the sending symbols on the orthogonal branches, and because the signals of different orthogonal branches are separated on the time domain, the sending symbols of different orthogonal branches can be independently demodulated without joint solution, thereby reducing the complexity; after signal extraction, symbol demodulation can be realized by performing DFT (discrete fourier transform), multiplication by a phase factor and IDFT (inverse discrete fourier transform), and since IDFT can be realized by FFT, the implementation complexity is low, so the receiving end of the multi-carrier system has low implementation complexity.
The invention adopts the preset delay coefficient K equal to the number R of the orthogonal branches, and the main reason is that when the preset delay coefficient K is less than the number R of the orthogonal branches, the multi-carrier communication system is easy to generate interference and cannot demodulate a sending symbol.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (5)

1. A cyclic prefix based multi-carrier method, comprising:
(1) synchronously performing inverse discrete Fourier transform on all subcarrier sending symbols in each orthogonal branch to obtain a time domain sending signal, wherein each orthogonal branch corresponds to M subcarriers, M is a subcarrier serial number, and M is 1, … and M;
(2) synchronously delaying the time domain sending signals transmitted on each orthogonal branch in sequence by rT and multiplying the time domain sending signals by corresponding phase factors ej2 πrp/RAcquiring time domain orthogonal signals on each orthogonal branch;
(3) synchronously superposing the time domain orthogonal signals acquired from each orthogonal branch, and then performing cyclic prefix processing to acquire a transmitting signal of a transmitting end; the transmission signal is converted into a reception signal at a receiving end, and a demodulation process of the reception signal includes S1-S5:
s1, converting the received signal into a frequency domain received signal without cyclic prefix and then performing channel equalization;
s2, judging whether the serial number of the orthogonal branch after channel equalization is 0, if so, the equalization signal at the mR position after channel equalization is the sending symbol of the 0 th orthogonal branch, otherwise, turning to the step S3;
s3, extracting the equalizing signal with the sequence number mR + p as the sending signal of the p-th orthogonal branch;
s4, performing inverse discrete fourier transform on the transmission signal acquired in step S3, and segmenting the transmission signal in units of one symbol period;
the S5 segmented transmission signals are all multiplied by corresponding phase factors ej2πrp/RThen, discrete Fourier transform is carried out to obtain symbol demodulation of each orthogonal branch;
wherein r is an integer set [0, K ]; k is a preset delay coefficient; t is a symbol period; k is more than or equal to the number R of the orthogonal branches; p is the serial number of the quadrature branch.
2. The multi-carrier method according to claim 1, characterized in that said preset delay factor K is equal to the number R of orthogonal branches.
3. The multi-carrier method according to claim 1, wherein the S1 specifically includes:
s1.1, removing a cyclic prefix in a received signal;
s1.2, performing discrete Fourier transform on the received signal without the cyclic prefix to obtain a frequency domain received signal without the cyclic prefix;
s1.3, channel equalization is carried out on the frequency domain received signal with the cyclic prefix removed.
4. A cyclic prefix based multi-carrier system, comprising: the system comprises a carrier loader, an orthogonal branch, a first Fourier inverse transformer, a signal delayer and a cyclic prefix processor which are connected in sequence, and a receiver, a cyclic prefix removing processor, a first Fourier transformer, a channel equalizer, an extraction module, a second Fourier inverse transformer, a phase modulator and a second Fourier transformer which are connected in sequence;
the orthogonal branch is used for synchronously transmitting a sending symbol; the carrier loader is configured to load the transmission symbol on the orthogonal branches, where each orthogonal branch corresponds to M subcarriers, M is a subcarrier sequence number, and M is 1, …, and M; the first inverse fourier transformer is configured to perform inverse discrete fourier transform on the transmission symbols transmitted in each of the orthogonal branches; the signal delayer is used for sequentially delaying the time domain transmission signals by rT, andmultiplied by a corresponding phase factor ej2πrp/RAcquiring time domain orthogonal signals on each orthogonal branch; the cyclic prefix processor is used for performing cyclic prefix processing after the time domain orthogonal signals acquired on each orthogonal branch are superposed to acquire transmitting signals;
the receiver is used for receiving the transmitting signal and converting the transmitting signal into a receiving signal; the processor is used for removing the cyclic prefix in the received signal; the first Fourier transformer is used for performing discrete Fourier transform on the transmission signal without the cyclic prefix; the channel equalizer is used for equalizing a frequency domain transmitting signal channel with the cyclic prefix removed; the extraction module is used for judging whether the serial number of the orthogonal branch is 0 or not, and if so, the equalized signal at the position of the mR after equalization is extracted is the sending symbol of the 0 th orthogonal branch; otherwise, extracting the equalization signal with the serial number mR + p as the transmission signal of the p-th orthogonal branch; the second inverse Fourier transformer is used for performing inverse discrete Fourier transform on the transmission signal of the p-th orthogonal branch to obtain a time-domain transmission signal; the phase modulator is used for dividing the time domain transmission signal by one symbol period and multiplying the time domain transmission signal by a phase factor ej2πrp/R(ii) a The second Fourier transformer is used for multiplying phase factor ej2πrp/RPerforming discrete Fourier transform on the transmitted signal to acquire symbol demodulation of each orthogonal branch;
wherein r is an integer set [0, K ]; k is a preset delay coefficient; t is a symbol period; k is more than or equal to the number R of the orthogonal branches; p is the serial number of the quadrature branch.
5. A multi-carrier system as claimed in claim 4, characterized in that said predetermined delay factor K is equal to the number R of orthogonal branches.
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