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

Abstract

The invention discloses a cyclic prefix-based multi-carrier method and system, belonging to the technical field of communications, comprising: synchronously performing inverse discrete Fourier transform on all sub-carrier transmission symbols in each orthogonal branch to obtain time-domain transmission signals; The time-domain transmission signals transmitted on each quadrature branch are sequentially delayed by rT for synchronization, and are multiplied by the corresponding phase factor e ^j2πrp/R to obtain the time-domain quadrature signal on each quadrature branch; After superimposing the time-domain orthogonal signals of , perform cyclic prefix processing to obtain the transmitted signal of the transmitting end; where r is the set of integers [0, K]; T is the symbol period; K is greater than or equal to the number R of orthogonal branches; p is the The sequence number of the orthogonal branch. Each transmission symbol transmitted by the orthogonal branch provided by the present invention is repeatedly delayed K times, only a section of CP needs to be inserted at every KM sampling point, and the maximum number of orthogonal branches is not greater than the preset delay coefficient, Therefore, the present invention does not increase the system bit error rate while reducing the CP overhead of the multi-carrier communication system.

Description

A multi-carrier method and system based on cyclic prefix

technical field

The present invention belongs to the field of communication technologies, and more particularly, to a cyclic prefix-based multi-carrier method and system.

Background technique

Multi-carrier communication technology, especially Orthogonal Frequency Division Multiplexing (OFDM) communication technology, has been widely used in wireless communication. A significant disadvantage of OFDM technology is that each OFDM symbol needs to insert a cyclic prefix (CP) to effectively resist the influence of multipath fading channels. However, the insertion of CP in each OFDM symbol significantly reduces the multi-carrier communication system. energy efficiency and spectral efficiency. At present, the methods for reducing the CP overhead of multi-carrier communication mainly include two categories:

(1) Iterative method, "P. Torres and A. Gusmao, "Iterative receiver technique for reduced-CP, reduced-PMEPR OFDM transmission," IEEE Vehicular Technology Conference, pp. 1981-1985, May 2007," discloses directly reducing the length of CP Inter-symbol interference and inter-carrier interference are introduced. This method is not only complex, but also cannot completely eliminate inter-carrier interference and inter-symbol interference. When a high-bit-rate debugging method is adopted, the bit error rate of a multi-carrier communication system will increase.

(2) Filter method, "P.Siohan,C.Siclet and N.Lacaille,"Analysis and design of OQAM-OFDM systems based on filterbank theory,"IEEE Transactions on SignalProcessing,vol.50,no.5,pp.1170 -1183, May.2002" discloses that the transmitted symbol of each sub-carrier of the multi-carrier communication system passes through a prototype filter with time-frequency two-dimensional focusing. Due to the use of a non-rectangular window filter, the multi-carrier communication system cannot insert a loop prefix. However, the multi-carrier communication system cannot effectively fight against multi-path fading channels. In the case of a large bandwidth of the multi-carrier communication system, the multi-carrier communication system has great interference and poor bit error rate.

(3) Precoded OFDM, "X.-G.Xia, "Precoded and vector OFDM robust to channelspectral nulls and with reduced cyclic prefix length in single transmit antenna systems," IEEE Transactions on Communications, vol.49, no.8, pp .1363-1374, Aug.2001" discloses that the multi-carrier communication system precodes multiple symbols, the precoding matrix is a unit matrix, and intercepts the tail section of the signal to form a cyclic prefix and sends it through the transmitting antenna. At the receiving end, it can pass the channel diagonal Processing simplifies receiver complexity. The multi-carrier communication system can greatly reduce the CP overhead of the OFDM technology without affecting the bit 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.

To sum up, the disadvantages of the current method for reducing the CP overhead in the multi-carrier system include: increased bit error rate or high complexity in the multi-carrier communication system.

SUMMARY OF THE INVENTION

In view of the defects of the prior art, the purpose of the present invention is to provide a multi-carrier method and system based on a cyclic prefix, aiming to solve the problem of increased system bit error rate in the existing method for reducing CP overhead of a multi-carrier communication system.

In order to achieve the above object, on the one hand, the present invention provides a multi-carrier method based on a cyclic prefix, including:

(1) synchronously perform inverse discrete Fourier transform on all sub-carrier transmission symbols in each orthogonal branch to obtain time-domain transmission signals;

(2) Synchronously delay the time-domain transmission signals transmitted on each quadrature branch by rT in turn, and multiply by the corresponding phase factor e ^j2πrp/R to obtain the time-domain quadrature signals on each quadrature branch;

(3) Synchronously perform cyclic prefix processing on the time-domain quadrature signals acquired on each quadrature branch after superposition, and acquire the transmit signal of the transmitter;

Wherein, r is a set of integers [0, K]; K is a preset delay coefficient; T is a symbol period; K is greater than or equal to the number R of the orthogonal branches; p is the serial number of the orthogonal branches.

Preferably, the preset delay coefficient K is equal to the number R of orthogonal branches;

Preferably, the transmitted signal is converted into a received signal at the receiving end, and the demodulation process of the received signal is:

a. Remove the cyclic prefix in the received signal;

b. Perform discrete Fourier transform on the received signal with the cyclic prefix removed to obtain the received signal in the frequency domain with the cyclic prefix removed;

c. Equalize the received signal channel in the frequency domain with the cyclic prefix removed;

d. Judge whether the sequence number of the orthogonal branch after channel equalization is 0, and if so, the equalized signal at the mRth position after equalization is the transmission symbol of the 0th orthogonal branch; otherwise, go to step e;

e. Extract the equalized signal at mR+p as the transmission signal of the p-th quadrature branch;

f. Perform inverse discrete Fourier transform on the acquired transmitted signal to obtain the transmitted signal in the time domain;

g. The time domain transmission signal is segmented in units of one symbol period;

h. The transmitted signals after the segmentation are all multiplied by the phase factor e ^j2πrp/R ;

i. Perform discrete Fourier transform on the transmitted signal multiplied by the phase factor e ^j2πrp/R to obtain symbol demodulation of each quadrature branch.

In another aspect, the present invention provides a cyclic prefix-based multi-carrier system, comprising: an orthogonal branch, a carrier loader, a first inverse Fourier transform, a signal delay, and a cyclic prefix processor;

The input end of the quadrature branch is connected to the carrier loader; the output end of the quadrature branch is connected to the first inverse Fourier transformer, the signal delay device and the cyclic prefix processor in sequence;

The orthogonal branch is used for synchronously transmitting the transmitted symbols; the carrier loader is used to load the transmitted symbols on the orthogonal branch; the first inverse Fourier transform is used to perform discrete Fourier transformation on the transmitted symbols transmitted in each orthogonal branch Inverse transform to obtain the time-domain transmission signal; the signal delay device is used to sequentially delay the time-domain transmission signal by rT, and multiply it by the corresponding phase factor e ^{j2 πrp/R} to obtain the time-domain quadrature signal on each quadrature branch; cyclic prefix processing The device is used to process the cyclic prefix after superposition of the time-domain quadrature signals obtained on each quadrature branch to obtain the transmitted signal;

Wherein, r is a set of integers [0, K]; K is a preset delay coefficient; T is a symbol period; K is greater than or equal to the number R of the orthogonal branches; p is the serial number of the orthogonal branches.

Preferably, K is equal to the number R of orthogonal branches;

Preferably, the cyclic prefix-based multi-carrier system further comprises: a receiver connected in sequence, a de-cyclic prefix processor, a first Fourier transformer, a channel equalizer, an extraction module, a second inverse Fourier transformer, Phase modulator, second Fourier transformer;

The cyclic prefix removal processor is used to remove the cyclic prefix in the transmitted signal; the first Fourier transformer is used to perform discrete Fourier transform on the cyclic prefix-removed transmitted signal, and convert it from a time domain signal to a frequency domain signal; channel equalization The device is used to equalize the frequency domain transmission signal channel with the cyclic prefix removed; the extraction module is used to determine whether the serial number of the quadrature branch is 0, and if so, the equalized signal at the mRth position after the extraction and equalization will be the 0th quadrature branch. Otherwise, the equalized signal at the position of the extraction sequence number mR+p is the transmitted signal of the p-th quadrature branch; the second inverse Fourier transform is used to convert the transmitted signal of the p-th quadrature branch. The inverse discrete Fourier transform is used to obtain the time-domain transmission signal; the phase modulator is used to segment the time-domain transmission signal in units of one symbol period and then multiply it by the phase factor e ^j2πrp/R ; The second Fourier transformer is used to multiply The discrete Fourier transform is performed on the transmitted signal with the phase factor e ^j2πrp/R , and the symbol demodulation of each quadrature branch is obtained.

Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

(1) The multi-carrier method and system based on the cyclic prefix provided by the present invention, the transmitting end has multiple orthogonal branches, which can transmit multiple symbols at the same time, and the maximum number of orthogonal branches is not greater than the preset delay coefficient K, obtain repeated symbols, otherwise the multi-carrier communication system is prone to interference, and the repeated symbols of each orthogonal branch in the multi-carrier system are multiplied by the phase factor after discrete Fourier transform, and the phase factors of different orthogonal branches are It is orthogonal to ensure the interference-free transmission of symbols. At the same time, it is assumed that there are R orthogonal branches, and each orthogonal branch contains M subcarriers. The traditional OFDM needs to insert a CP every M sampling points, while the present invention Since each transmitted symbol transmitted by the orthogonal branch is repeatedly delayed K times, only a segment of CP needs to be inserted every KM sampling points. Therefore, the present invention does not increase the system bit error rate while reducing the CP overhead of the multi-carrier communication system. .

(2) In the present invention, since the received signals of the transmitted symbols of different orthogonal branches are separated in the time domain, in order to recover the transmitted symbols on the orthogonal branches, signal extraction is required, because the signals of different orthogonal branches are in the It is separated in time, so the transmitted symbols of different orthogonal branches can be demodulated independently without joint solution, which reduces the complexity; after signal extraction, DFT (discrete Fourier transform), multiplication Symbol demodulation can be realized by using phase factor and IDFT (Inverse Discrete Fourier Transform). Since IDFT can be realized by FFT, the realization complexity is low. Therefore, the receiving end of the multi-carrier system has low realization complexity.

(3) The present invention adopts the preset delay coefficient K equal to the number R of orthogonal branches, the main reason is that when the preset delay coefficient K is less than the number R of orthogonal branches, it will cause a multi-carrier communication system Interference is prone to occur, and the transmitted symbols cannot be demodulated. When the preset delay coefficient K is greater than the number R of the orthogonal branches, it will cause a waste of time and reduce the energy efficiency and spectral efficiency of the system. Therefore, when the preset delay coefficient K is equal to the number R of orthogonal branches, it can ensure that the energy efficiency and spectral efficiency of the system are not reduced, and the bit error rate of the system is not increased.

Description of drawings

1 is a multi-carrier method based on a cyclic prefix provided by an embodiment;

FIG. 2 is a schematic diagram of a demodulation process based on the transmission signal of FIG. 1 provided by an embodiment.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In one aspect, the present invention provides a cyclic prefix-based multi-carrier method, including:

(1) synchronously perform inverse discrete Fourier transform on all sub-carrier transmission symbols in each orthogonal branch to obtain time-domain transmission signals;

It is preset that each orthogonal branch corresponds to M subcarriers, and the mth subcarrier is loaded with a transmission symbol x _m,p on each orthogonal branch, and the transmission symbol x _m,p is generated by M-point IDFT (Inverse Discrete Fourier Transform) Send signal; wherein, m is the subcarrier sequence number; p is the sequence number of the quadrature branch; M, m and p are integers greater than or equal to 0;

(2) Synchronously delay the time-domain transmission signals transmitted on each quadrature branch by rT in turn, and multiply by the corresponding phase factor e ^j2πrp/R to obtain the time-domain quadrature signals on each quadrature branch;

A time-domain transmission signal on a certain quadrature branch is delayed by 0, MT _s , 2MT _s , ..., KMT _s in turn, and is multiplied by the phase factor e ^j2πrp/R , where T=MT _s , T _s is the sampling interval, r is the integer set [0, K]; K is the preset delay coefficient; T is the symbol period; K is greater than or equal to the number R of orthogonal branches;

(3) Synchronization The time-domain quadrature signals obtained on each quadrature branch are superimposed, and then cyclic prefix processing is performed to obtain the transmitted signal.

The delayed time-domain quadrature signal is superimposed to form an extended time-domain orthogonal signal, the tail of the extended time-domain orthogonal signal is intercepted and inserted into the starting position of the extended time-domain orthogonal signal to form a cyclic prefix, and the transmitted signal is obtained and sent through the transmitting antenna .

Preferably, the preset delay coefficient K is equal to the number R of orthogonal branches;

Preferably, the transmitted signal is converted into a received signal at the receiving end, and the demodulation process of the received signal is:

a. Remove the cyclic prefix in the received signal;

b. Perform KM point discrete Fourier transform on the received signal with the cyclic prefix removed, and obtain the received signal in the frequency domain with the cyclic prefix removed;

c. Equalize the frequency domain transmission signal channel with the cyclic prefix removed;

d. Judge whether the sequence number of the orthogonal branch after channel equalization is 0, and if so, the equalized signal at the mRth position after equalization is the transmission symbol of the 0th orthogonal branch; otherwise, go to step e;

e. Extract the equalized signal at mR+p as the transmission signal of the p-th quadrature branch;

f. Perform inverse discrete Fourier transform on the transmission signal obtained in step e to obtain the time-domain transmission signal;

g. The time domain transmission signal is segmented in units of one symbol period;

h. The transmitted signals after the segmentation are all multiplied by the phase factor e ^j2πrp/R ;

i. Perform discrete Fourier transform on the transmitted signal multiplied by the phase factor e ^j2πrp/R to obtain symbol demodulation of each quadrature branch.

In another aspect, the present invention provides a cyclic prefix-based multi-carrier system, comprising: an orthogonal branch, a carrier loader, a first inverse Fourier transform, a signal delay, and a cyclic prefix processor;

Each quadrature branch is connected to the carrier loader; the output end of the quadrature branch is connected to the first inverse Fourier transformer, the signal delayer and the cyclic prefix processor in sequence;

The quadrature branch is used to transmit the transmitted symbols synchronously; the carrier loader is used to load the transmitted symbols on the orthogonal branch; the first inverse Fourier transform is used to perform inverse discrete Fourier transform on the transmitted symbols transmitted in each branch , to obtain the time-domain transmission signal; the signal delayer is used to sequentially delay the time-domain transmission signal by rT, and multiply it by the corresponding phase factor e ^j2πrp/R to obtain the time-domain quadrature signal on each quadrature branch; the cyclic prefix processor is used to The time-domain quadrature signals obtained on each quadrature branch are superimposed and processed with a cyclic prefix to obtain the transmitted signal;

Wherein, r is a set of integers [0, K]; K is a preset delay coefficient; T is a symbol period; K is greater than or equal to the number R of the orthogonal branches; p is the serial number of the orthogonal branches.

Preferably, K is equal to the number R of orthogonal branches;

Preferably, the cyclic prefix-based multi-carrier system further comprises: a receiver connected in sequence, a de-cyclic prefix processor, a first Fourier transformer, a channel equalizer, an extraction module, a second inverse Fourier transformer, Phase modulator, second Fourier transformer;

The receiver is used to receive the transmitted signal and convert it into a received signal; the de-cyclic prefix processor is used to remove the cyclic prefix in the received signal; the first Fourier transformer is used to perform discrete Fourier transform on the received signal with the cyclic prefix removed , convert it from the time domain signal to the frequency domain signal; the channel equalizer is used to equalize the received signal channel in the frequency domain with the cyclic prefix removed; the extraction module is used to judge whether the serial number of the quadrature branch is 0, if so, it will extract the equalized The equalized signal at the mRth position is the transmitted symbol of the 0th quadrature branch; otherwise, the equalized signal at the extraction sequence number mR+p is the transmitted signal of the pth quadrature branch; the second Fourier inverse The transformer is used to perform inverse discrete Fourier transform on the transmitted signal of the p-th quadrature branch to obtain the transmitted signal in the time domain; the phase modulator is used to segment the transmitted signal in the time domain by a symbol period and multiply it by the phase factor e ^j2πrp/R ; the second Fourier transformer is used to perform discrete Fourier transform on the transmitted signal multiplied by the phase factor e ^j2πrp/R to obtain symbol demodulation of each quadrature branch.

Example

The embodiment provides a multi-carrier system with 2048 subcarriers, wherein the symbol mapping method adopts 4QAM mapping method, the maximum repetition times of each symbol is R=2, and the maximum number of orthogonal branches is 2. Let the transmitted symbol be am _,p , where 0≤m<2048 is the sequence number of the subcarrier, and 0≤p<2 is the sequence number of the orthogonal branch.

As shown in FIG. 1, the embodiment provides a multi-carrier method based on a cyclic prefix, as follows:

所述n、m和p为整数序号且0≤n＜2048和0≤p＜2；(1) For each quadrature branch at the transmitting end, the frequency domain symbol x _m,p generates a time domain signal through the IDFT operation of 2048 points

The n, m and p are integer serial numbers and 0≤n<2048 and 0≤p<2;

(2) For each quadrature branch, delay the time domain signal sp (n) generated after IDFT by rT, an integer set of _r∈ [0,1], where T is the symbol period;

(3) Multiply the signal generated in step (2) by the corresponding phase factor, which can be expressed as

尾部的一段信号，并插入起始位置形成循环前缀，最终经发射天线发送；(4) Intercept the signal

A segment of the signal at the tail is inserted into the starting position to form a cyclic prefix, and finally sent through the transmitting antenna;

As shown in FIG. 2, the embodiment provides a demodulation process of the received signal, which is as follows:

(5) At the receiving end, the cyclic prefix of the front part is truncated from the received signal;

对于p≥1，符号解调转入步骤(7)-步骤(9)；(6) Perform DFT on the signal obtained in step (5), the length of the DFT is 2 times 2048, and then perform frequency domain channel equalization on the obtained signal to obtain r(n); for p=0, the mR position after frequency domain equalization The signal at is the transmitted symbol of the recovered 0th quadrature branch

For p≥1, the symbol demodulation goes to step (7)-step (9);

(7) Perform signal extraction for the symbol of each quadrature branch respectively. For the p-th quadrature branch, extract the signal r(2m+p) at the serial number 2m+p, and the other positions of the signal are 0, that is, r(2m+q) is set to 0, where q≠p;

其中n＝0,1,…,4095，然后将信号以一个符号周期为单位进行分段，如果要恢复第p个正交支路的发送符号时，则乘以第p个正交支路的相位因子e^-j2πrp/2。信号

乘以相位因子e^-j2π0p/2，信号

乘以相位因子e^-j2πp/2；(8) Perform 4096-point IDFT on the signal obtained in step (7) to obtain the signal

where n=0,1,...,4095, then the signal is segmented in units of one symbol period. If the transmitted symbol of the p-th quadrature branch is to be recovered, multiply it by the Phase factor e ^-j2πrp/2 . Signal

Multiplied by the phase factor e ^-j2π0p/2 , the signal

Multiply by the phase factor e ^-j2πp/2 ;

(9) 4096-point DFT is performed on the signals obtained in step (8) respectively, and symbol demodulation of each quadrature branch can be realized.

To sum up, the cyclic prefix-based multi-carrier method and system provided by the present invention has multiple orthogonal branches at the transmitting end, and can transmit multiple symbols at the same time, and the maximum number of orthogonal branches is not greater than the preset number. The delay coefficient K is used to obtain the repeated symbols, otherwise the multi-carrier communication system is prone to interference, and the repeated symbols of each orthogonal branch in the multi-carrier system are multiplied by the phase factor after discrete Fourier transform. The phase factor is orthogonal to ensure the interference-free transmission of symbols. At the same time, it is assumed that there are R orthogonal branches, and each orthogonal branch contains M subcarriers. In traditional OFDM, a CP needs to be inserted every M sampling points, while Since the present invention adopts orthogonal branches and repeats delay K times for each transmitted symbol, it only needs to insert a section of CP at every KM sampling point. Therefore, the present invention does not increase the system error while reducing the CP overhead of the multi-carrier communication system. code rate.

In the present invention, since the received signals of the transmitted symbols of different orthogonal branches are separated in the time domain, in order to recover the transmitted symbols on the orthogonal branches, signal extraction needs to be performed, because the signals of different orthogonal branches are temporally Therefore, the transmitted symbols of different orthogonal branches can be demodulated independently without joint solution, which reduces the complexity; after signal extraction, DFT (discrete Fourier transform), multiplied by the phase factor And IDFT (Inverse Discrete Fourier Transform) can realize symbol demodulation. Since IDFT can be realized by FFT, the realization complexity is low. Therefore, the receiving end of the multi-carrier system has lower realization complexity.

The present invention adopts the preset delay coefficient K equal to the number R of orthogonal branches, the main reason is that when the preset delay coefficient K is less than the number R of orthogonal branches, the multi-carrier communication system is prone to interference , the transmitted symbols cannot be demodulated. When the preset delay coefficient K is greater than the number R of orthogonal branches, it will bring waste of time and reduce the energy efficiency and spectral efficiency of the system. Therefore, when When the preset delay coefficient K is equal to the number R of orthogonal branches, it can ensure that the energy efficiency and spectral efficiency of the system are not reduced, and that the bit error rate of the system is not increased.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection 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 e^{j2 πrp/R}Acquiring 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 e^j2πrp/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 e^j2πrp/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 e^j2πrp/R(ii) a The second Fourier transformer is used for multiplying phase factor e^j2πrp/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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