CN101986631A - Time- and frequency-domain unified single carrier modulation signal transmission method - Google Patents

Abstract

The invention relates to a signal transmission method using time-frequency domain combined single-carrier modulation, which belongs to the technical field of digital information transmission. The method first performs source coding, channel coding and constellation mapping on the information generated by the sending end in sequence, and obtains the mapped information. information; perform TFU-SCM modulation on the mapped information, and send multiple modulated symbols into a frame signal; split the received frame signal into TFU-SCM modulation symbols according to the corresponding composition method; Perform TFU-SCM demodulation to obtain serial data, which is sequentially subjected to constellation inverse mapping, channel decoding, and source decoding to obtain the original information. The method of the present invention retains the advantages of low complexity at the sending end of SC-FDE technology, and can flexibly select the number of UWs in the pilot according to the requirements of system performance, and can conveniently select the number of UWs in the pilot by operating the pilot in the frequency domain. Synchronization, channel estimation, equalization and other operations are carried out, which improves the processing efficiency of the system and is more suitable for broadband wireless mobile communication systems.

Description

A Signal Transmission Method Using Single Carrier Modulation Using Time-Frequency Domain Joint

technical field

The invention belongs to the technical field of digital information transmission, and in particular relates to a single-carrier modulation technology in a broadband wireless mobile communication system.

Background technique

In a broadband wireless mobile communication system, the transmitted signal is often affected by occlusion, absorption, reflection, refraction and diffraction caused by various objects in the environment during the propagation process, forming multiple path signal components to reach the receiver. The signal components of different paths have different propagation delays, phases and amplitudes, and channel noise is added, and their superposition will make the composite signal cancel or enhance each other, resulting in severe fading. This fading will distort the received signal of the receiver and reduce the reliability of communication. In addition, if the transmitter or the receiver is in a relatively moving state, the received signal will be more seriously distorted due to the Doppler effect. Traditional time-domain equalization can eliminate intersymbol interference (InterSymbol Interference, hereinafter referred to as ISI) caused by multipath. It uses the time waveform generated by the equalizer to directly correct the distorted waveform, so that the entire system including the equalizer The impulse response of satisfies the condition of no intersymbol interference. Since the computational complexity of time domain equalization is directly proportional to the maximum delay spread, this greatly increases the complexity of the time domain equalization system and limits its application in broadband wireless mobile communications. (The so-called maximum delay extension refers to the difference between the maximum transmission delay and the minimum transmission delay, that is, the difference between the arrival time of the last resolvable delay signal and the first delay signal, which is actually the difference of pulse stretching time.)

The signal transmission process of an Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) system is shown in Figure 1. After source coding and channel coding, the source is subjected to constellation mapping to obtain the data stream, and then the data stream is converted into multiple parallel data blocks and the data block is transformed by Inverse Fast Fourier Transform (hereinafter referred to as IFFT). to the time domain, and finally insert a cyclic prefix (Cyclic Prefix, hereinafter referred to as CP) before each data block in the time domain to form an OFDM signal and transmit it; the OFDM signal reaches the receiving end after being transmitted through the channel, and the receiving end removes the received signal After CP, fast Fourier transform (Fast Fourier Transform, hereinafter referred to as FFT) is performed to convert back to the frequency domain, and after equalization, constellation inverse mapping, channel decoding, and source decoding are performed to restore the original information (sink).

The above method is an efficient modulation method, and the transmission method is widely used in various fields of broadband wireless mobile communication because of its advantages such as high spectrum utilization rate and resistance to frequency selective fading. However, OFDM also has shortcomings such as too large Peak to Average Power Ratio (hereinafter referred to as PAPR) and sensitivity to frequency offset. Compared with OFDM, as another effective method against channel fading characteristics in broadband wireless mobile communications, Single Carrier-Frequency Domain Equalization (Single Carrier-Frequency Domain Equalization, hereinafter referred to as SC-FDE) was proposed. The signal transmission of its system The process is shown in Figure 2, including the following steps;

(1) Perform source coding, channel coding and constellation mapping on the information to be sent by the sending end in sequence to obtain the mapped information;

(2) After the above-mentioned mapped information is divided into blocks, add CP at the front end of each block to form an SC-FDE symbol and then emit it;

(3) The receiving end receives the above-mentioned SC-FDE symbols from the channel;

(4) remove the CP in the SC-FDE symbol after synchronizing the above-mentioned SC-FDE symbol, obtain the data block in the SC-FDE symbol;

(5) Carry out FFT operation to above-mentioned data block, it is converted into frequency domain;

(6) Equalize the data converted into the frequency domain by using the channel information obtained from the channel estimation to obtain equalized frequency domain data;

(7) IFFT operation is performed on the frequency domain data after equalization, and it is converted back to the time domain;

(8) Perform constellation inverse mapping, channel decoding and source decoding on the data converted back to the time domain to restore the original information (sink).

Compared with OFDM, the above SC-FDE method has the following advantages:

(1) What SC-FDE transmits in the channel is a signal modulated directly in the time domain, and the envelope is a multi-ary phase shift keying (Multiple Phase Shift Keying, hereinafter referred to as MPSK) or a multi-ary quadrature amplitude modulation ( Multiple Quadrature Amplitude Modulation (hereinafter referred to as MQAM) signal has a relatively constant envelope and low PAPR, while an OFDM signal is composed of a series of subcarrier signals overlapping, and when the phases of each subcarrier are the same, it will produce a high PAPR. Therefore, compared with OFDM, SC-FDE reduces radio frequency cost.

(2) Different from the non-adaptive OFDM system, SC-FDE can resist frequency selectivity without coding.

(3) SC-FDE is not sensitive to carrier frequency offset, which reduces the cost of frequency synchronization when receiving signals.

Through the comparison of Figure 1 and Figure 2, it can be seen that single carrier frequency domain equalization is developed from FFT-based OFDM, which divides the serially transmitted and received data into blocks of the same size at the receiving end, and performs The frequency domain representation is obtained by FFT processing. In the frequency domain, the channel estimation result is divided by the channel gain of the frequency point at each frequency point. After equalization, the time domain signal is recovered by IFFT processing for decoding. (The so-called channel estimation is the process of estimating the model parameters of an assumed channel model from the received data.)

The SC-FDE frame structure is shown in Figure 3. Copy a piece of data at the end of each data block and place it in front of the data block as CP to eliminate ISI. Each data block and its leading CP form an SC-FDE symbol. Due to the unknown nature of CP, it is difficult for SC-FDE method to use CP to perform operations such as synchronization, channel estimation, and equalization. Even if these functions can be realized, the algorithm complexity is relatively high.

Contents of the invention

The object of the present invention is to propose a signal transmission method using time-frequency domain combined single-carrier modulation to overcome the shortcomings of the prior art. The method not only retains the advantages of low complexity at the transmitting end of the single-carrier frequency domain equalization technology, but also makes the estimation of the channel response at the receiving end more accurate, and is more suitable for broadband wireless mobile communication systems.

The signal transmission method adopting the single-carrier modulation of time-frequency domain joint that the present invention proposes, comprises the following steps:

(1) Perform source coding, channel coding and constellation mapping on the information to be sent by the sending end in sequence to obtain the mapped information;

(2) performing joint single-carrier modulation in the time-frequency domain on the above-mentioned mapped information to obtain joint single-carrier modulation symbols in the time-frequency domain;

The specific steps of the single carrier modulation are as follows:

(a) converting the above-mentioned mapped information into multiple parallel data blocks;

(b) Select a Chu sequence or a Frank-Zadoff sequence as the UW sequence, and arrange one UW or multiple UWs together to form a pilot block;

(c) Inserting a UW at the rear end of each parallel data block mentioned above as a guard interval to form an FFT block;

(d) Insert the above-mentioned pilot block at the front end of the FFT block, and form a joint single-carrier modulation symbol in the time-frequency domain by the pilot block and the FFT block;

(3) Composing the single-carrier modulation symbols combined in the time-frequency domain of each channel into a frame signal and sending it;

(4) The receiving end receives the frame signal composed of the above-mentioned time-frequency domain joint single-carrier modulation symbols, and splits the received frame signal into multiple parallel time-frequency domain joint single-carrier modulation symbols according to the corresponding composition mode;

(5) Composing a serial data stream after performing combined single-carrier demodulation in the time-frequency domain on the single-carrier modulation symbols combined in the time-frequency domain;

The specific steps of the single carrier demodulation are as follows:

(a1) Use the pilot in the TFU-SCM symbol to perform symbol synchronization and carrier synchronization on the received single-carrier modulation symbols in the time-frequency domain. The pilot block in the carrier modulation symbol is separated from the FFT block to obtain separated FFT blocks;

(b1) performing Fourier transform on the above-mentioned FFT block to obtain a frequency-domain signal corresponding to the time-domain FFT block;

(c1) Utilize the pilot blocks in the combined single-carrier modulation symbols of each time-frequency domain to estimate the frequency-domain gain of each frequency point of the channel when the corresponding single-carrier modulation symbols of the time-frequency domain combination pass through the channel, and use the gain to (b1 ) to perform channel equalization on the corresponding frequency domain signal to obtain an equalized signal;

(d1) performing an IFFT operation on the above-mentioned equalized frequency domain signal, removing the UW at the back end of each data block, and merging multiple parallel data blocks into a serial data stream;

(6) Constellation inverse mapping, channel decoding, and source decoding are performed sequentially on the above serial data stream to obtain original information.

The advantages of the signal transmission method using time-frequency domain combined single-carrier modulation proposed by the present invention are: the number of UWs in the pilot can be flexibly selected according to the requirements of system performance, and the operation of the pilot in the frequency domain can facilitate Synchronization, channel estimation and equalization are performed at the receiving end. This not only retains the advantages of low complexity at the transmitting end of the single-carrier frequency domain equalization technology, but also makes the estimation of the channel response at the receiving end more accurate. It still has very good performance under the channel condition of frequency selective fading or time selective fading. Compared with the existing signal transmission method, the method of the invention is more suitable for the broadband wireless mobile communication system.

Description of drawings

Fig. 1 is a system composition block diagram of existing OFDM technology.

Fig. 2 is a system composition block diagram of the existing SC-FDE technology.

Fig. 3 is a block diagram of symbol structure in the existing SC-FDE technology.

Fig. 4 is a block diagram of the TFU-SCM symbol structure in the signal transmission method proposed by the present invention.

Fig. 5 is a flow chart of signal transmission in the signal transmission method proposed by the present invention.

FIG. 6 is a flow chart of signal reception in the signal transmission method proposed by the present invention.

Detailed ways

A signal transmission method using time-frequency domain combined single-carrier modulation proposed by the present invention is described in detail in conjunction with the accompanying drawings and embodiments as follows:

The present invention adopts the single-carrier modulation technology that adds pilots in the time domain, but uses the pilots in the frequency domain to perform operations such as synchronization, channel estimation, and equalization to combat multipath propagation and Doppler frequency deviation in broadband wireless mobile communications. The present invention refers to this technology as time-frequency domain United-Single Carrier Modulation (Time domain and Frequency domain United-Single Carrier Modulation, hereinafter referred to as TFU-SCM) technology. TFU-SCM uses a cyclic suffix composed of a unique word (Unique Word, hereinafter referred to as UW) as a guard interval, and a special training sequence composed of one or more UWs as a pilot (the UW in the pilot can be flexibly selected according to the requirements of system performance) number) to form a TFU-SCM symbol, and through the operation of the pilot in the frequency domain, operations such as synchronization, channel estimation, and equalization can be conveniently performed at the receiving end. The structure of the TFU-SCM symbol is shown in Figure 4. It can be seen from Figure 4 that a TFU-SCM symbol includes two parts: one part is a pilot block composed of one or more UWs, and the other part is a data block and its following An FFT block composed of a UW.

A signal transmission method and embodiment of single carrier modulation using time-frequency domain combination proposed by the present invention, comprising the following steps:

(1) Perform source coding, channel coding, and constellation mapping on the information to be sent by the sending end in sequence to obtain the mapped information, as shown in front of the virtual frame in FIG. 5 . The coding method of the information source can be flexibly selected according to the information generated by the information source, such as Huffman coding, Feynau coding, Shannon coding and so on. The channel coding method can be convolutional code (Convolutional Code, CC), low density parity check code (Low Density Parity Check, LDPC), Reed-Solomon code (ReedSolomon, RS) and so on.

Constellation mapping is performed on the channel-coded information. The mapping method can be binary phase shift keying (Binary Phase Shift Keying, hereinafter referred to as BPSK), quadrature phase shift keying (Quadrature Phase Shift Keying, hereinafter referred to as QPSK), 16 points Quadrature amplitude modulation (16-Quadrature Amplitude Modulation, hereinafter referred to as 16QAM), 64-point quadrature amplitude modulation (64-Quadrature Amplitude Modulation, hereinafter referred to as 64QAM) and 256-point quadrature amplitude modulation (256-Quadrature Amplitude Modulation, hereinafter referred to as 256QAM )wait.

(2) Carry out TFU-SCM modulation to the above-mentioned modulated information, as shown in the dotted line box in Figure 5, the modulation steps are as follows:

(a) converting the modulated information into parallel data blocks;

(b) Generate a UW sequence, and use one or more UWs to form a pilot block (the higher the system performance requirement, the more the number of UWs in the pilot block, but the number of UWs does not exceed 4), in this embodiment UW selects the Chu sequence (proposed by DavidC.Chu) or the Frank-Zadoff sequence (proposed jointly by R.L.Frank and S.A Zadoff) as the UW sequence, whose length is a positive integer power of 2, and the maximum length does not exceed 256. When UW is used as a guard interval, the UW sequence length is not less than the maximum channel delay length. For example, when the system bandwidth is 10 MHz, the UW length can be 64, and the pilot block includes 4 UWs.

The in-phase (In-phase, hereinafter referred to as I) path and the quadrature (Quadrature, hereinafter referred to as Q) path signals of the UW sequence whose length is U (U is a positive integer) can be generated by the following formula respectively:

I[n]=cos(θ[n])

Q[n]=sin(θ[n])

Where n is any integer in the range of 0 to U-1.

There are two options for the phase θ[n]. When generating a Frank-Zadoff sequence, θ[n]=θ _Frank [n]; when generating a Chu sequence, θ[n]=θ _Chu [n].

The expression for θ _Frank [n] is:

${\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; Frank</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; q</span>}\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;pqr</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}}$

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

$\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

互素的整数。Where r = 1, 3 or with

Integers that are relatively prime.

The expression of θ _Chu [n] is:

${\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; Chu</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; u</span>}}$

n=0, 1, . . . , U-1

(c) inserting a UW at the rear end of each of the above-mentioned parallel data blocks as a guard interval to form an FFT block;

(d) Insert above-mentioned pilot block at the FFT block front end, form a TFU-SCM symbol by pilot block and FFT block, as shown in Figure 4;

(3) Send each TFU-SCM symbol into a frame signal;

(4) The receiving end receives the frame signal composed of the above TFU-SCM symbols, and splits the received frame signal into multiple parallel TFU-SCM symbols according to the corresponding composition mode;

(5) After carrying out joint single-carrier demodulation in the time-frequency domain to each road TFU-SCM symbol, form serial data flow; Described single-carrier demodulation is as shown in Fig. 6 dotted line frame, and its steps are as follows:

(a1) Use the pilot frequency of the TFU-SCM symbol to perform symbol synchronization and carrier synchronization on the above-mentioned received TFU-SCM symbols. According to the obtained symbol synchronization information, the pilot block in each TFU-SCM symbol The block and the FFT block of UW are separated to obtain the separated FFT block;

(b1) performing Fourier transform on the above-mentioned FFT block to obtain a frequency-domain signal corresponding to the time-domain FFT block;

(c1) Use the pilot blocks in each TFU-SCM symbol to estimate the frequency domain gain of each frequency point of the channel when the corresponding TFU-SCM symbol passes through the channel, and use the gain to perform channel equalization on the corresponding frequency domain signal in (b1) , to get the equalized signal. Among them, the algorithms of channel estimation and channel equalization can be flexibly selected. For example, channel estimation can adopt a channel estimation algorithm based on Discrete Fourier Transform (DFT for short), and channel equalization can adopt Zero Forcing (hereinafter referred to as DFT). ZF) equalization algorithm.

The channel estimation algorithm based on DFT in this embodiment is as follows:

Assuming that the frequency response of the channel remains unchanged when each symbol is sent, the length of the UW in the pilot block is L (L is a positive integer power of 2, and the maximum value does not exceed 256), using {x _m } (wherein, x Represents the signal in the time domain; m is any integer in the range of 0 to L-1), and the UW in the received pilot is represented by {y _m } (wherein, y represents the signal in the time domain; m is 0 to L-1) Any integer in the range of L-1) represents. First, perform L-point FFT operation on x _m and y _m respectively to obtain the sequence {X _k } (wherein, X represents the signal in the frequency domain; k is any integer ranging from 0 to L-1) and {Y _k } (wherein, X represents the signal in the frequency domain; k is any integer in the range of 0 to L-1), the estimated frequency response value H _k of each subchannel (wherein, k is any integer in the range of 0 to L-1 Integer) can be obtained by the following formula:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

(其中，i为0到M-1范围内的任一整数)。The frequency response characteristics of M (M is a positive integer, whose value is equal to the length of the FFT block) sub-channels are obtained by interpolation in the frequency domain. Perform L-point IFFT operation on {H _k }, add 0 to the end of the obtained sequence of length L to length M, and then perform M-point FFT operation to obtain the frequency response estimates of M sub-channels

(wherein, i is any integer in the range of 0 to M-1).

In order to improve the system performance, the pilot signal can be made to include multiple UWs, the channel is estimated multiple times, and then the average value is taken as the frequency response characteristics of the sub-channels, and finally the frequency response of all sub-channels is obtained by interpolation in the frequency domain. At the sending end, N (N is a positive integer) UWs are continuously sent as pilot blocks, and the average value of N estimates is taken:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{{{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

Wherein, n is any integer between 0 and N-1.

The ZF equalization algorithm is as follows:

The basic idea of ZF is that the sending end sends a training sequence, so there should be an ideal acceptance value correspondingly. After the training sequence is interfered by the ISI channel, the signal obtained at the receiving end must be different from this ideal value, and then this ideal value Compared with the disturbed value, the filter coefficient can be obtained. From the frequency domain, the frequency response of the disturbed signal is multiplied by a frequency response function (frequency response of the adaptive filter), so that it is equal to the frequency of the ideal received signal. ring.

The equalization coefficient of the ZF algorithm:

${\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}$

Among them, H _l is the estimated frequency response value of each sub-channel; l is a non-negative integer.

(d1) performing FFT on the above-mentioned equalized frequency domain signal, removing the UW at the back end of each data block, and merging multiple parallel data blocks into serial data;

(6) Constellation inverse mapping, channel decoding, and source decoding are performed sequentially on the received serial data to obtain original information. The constellation inverse mapping, channel decoding, and source decoding are performed according to the constellation mapping, channel coding, and source coding methods corresponding to the transmitting end (the specific implementations are all known technologies).

Claims (1)

1. A signal transmission method that adopts the joint single carrier modulation of time-frequency domain, it is characterized in that, the method comprises the following steps: (1) Perform source coding, channel coding, and constellation mapping on the information generated by the sending end in sequence to obtain mapped information; (2) performing joint single-carrier modulation in the time-frequency domain on the above-mentioned mapped information to obtain joint single-carrier modulation symbols in the time-frequency domain; The specific steps of the single carrier modulation are as follows: (a) converting the above-mentioned mapped information into multiple parallel data blocks; (b) Select a Chu sequence or a Frank-Zadoff sequence as the UW sequence, and arrange one UW or multiple UWs together to form a pilot block; (c) Inserting a UW at the rear end of each parallel data block mentioned above as a guard interval to form an FFT block; (d) Insert the above-mentioned pilot block at the front end of the FFT block, and form a joint single-carrier modulation symbol in the time-frequency domain by the pilot block and the FFT block; (3) Composing the single-carrier modulation symbols combined in the time-frequency domain of each channel into a frame signal and sending it; (4) The receiving end receives the frame signal composed of the above-mentioned time-frequency domain joint single-carrier modulation symbols, and splits the received frame signal into multiple parallel time-frequency domain joint single-carrier modulation symbols according to the corresponding composition mode; (5) Composing a serial data stream after performing combined single-carrier demodulation in the time-frequency domain on the single-carrier modulation symbols combined in the time-frequency domain; The specific steps of the single carrier demodulation are as follows: (a1) Use the pilot in the TFU-SCM symbol to perform symbol synchronization and carrier synchronization on the received single-carrier modulation symbols of the time-frequency domain combination, and synchronize each single-carrier modulation symbol of the time-frequency domain combination according to the obtained symbol synchronization information. The pilot block in the carrier modulation symbol is separated from the FFT block to obtain separated FFT blocks; (b1) performing Fourier transform on the above-mentioned FFT block to obtain a frequency-domain signal corresponding to the time-domain FFT block; (c1) Estimate the frequency domain gain of each frequency point of the channel when the corresponding time-frequency domain combined single-carrier modulation symbol passes through the channel by using the pilot block in the combined single-carrier modulation symbol of each time-frequency domain, and use the gain to (b1 ) to perform channel equalization on the corresponding frequency domain signal to obtain an equalized signal; (d1) performing an IFFT operation on the above-mentioned equalized frequency domain signal, removing the UW at the back end of each data block, and merging multiple parallel data blocks into a serial data stream; (6) Constellation inverse mapping, channel decoding, and source decoding are performed sequentially on the above serial data stream to obtain original information.

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