CN103973619A - Signal transmission method for single-carrier modulation with time-frequency domain combination - 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 channel coding and constellation mapping on the information generated by the sending end in order to obtain mapped symbols; A number of symbols after mapping form a data block, and a pilot composed of several UWs is inserted at the front end of the data block, and a UW is inserted at the back end to form a time-frequency domain joint single-carrier modulation symbol block; the receiving end uses The received time-frequency domain combines the pilot frequency at the front end of the data block in the single carrier modulation symbol block and the UW at the rear end to complete operations such as symbol synchronization, frequency synchronization, and frequency domain equalization, and sequentially perform constellation inverse mapping and channel decoding. Restore the original information. The method of the invention retains the advantages of low complexity at the sending end of SC-FDE technology, and makes the estimation of the channel response at the receiving end more accurate, the system processing efficiency is higher, and it is more suitable for the broadband wireless mobile communication system.

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. The traditional time-domain equalization can eliminate the 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.)

A signal transmission process of an Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) system is shown in FIG. 1 . After channel encoding, the information source is subjected to constellation mapping to obtain a data stream, and then the data stream is converted into multiple parallel data blocks, and the data blocks are subjected to Inverse Fast Fourier Transform (IFFT) to convert the data blocks into 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 performs Fast Fourier Transform (Fast Fourier Transform, hereinafter referred to as FFT) is converted back to the frequency domain, and after equalization, constellation inverse mapping and channel decoding are performed to restore the original information (sink).

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

1) Perform 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 transmit it;

3) The receiving end receives the above 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, convert it to frequency domain;

6) Using the channel information obtained from the channel estimation, equalizing the above-mentioned data converted into the frequency domain to obtain equalized frequency domain data;

7) Perform IFFT operation on the equalized frequency domain data, and convert it back to the time domain;

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

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

First, 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.

Second, unlike non-adaptive OFDM systems, SC-FDE does not use coding to combat frequency selectivity.

Third, 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 channel coding and constellation mapping on the information generated by the transmitting end in sequence to obtain multiple symbols after mapping;

2) a plurality of symbols after the above-mentioned mapping are formed into a parallel data block;

3) TFU-SCM modulation is performed on each data block: set UW as a reference sequence; insert a pilot composed of one or more UWs at the front end of the data block, and insert a UW at the back end as a guard interval, and the data The block and the back-end UW form an FFT block, and a time-frequency domain combined single-carrier modulation symbol (TFU-SCM symbol for short) block is formed by the pilot block and the FFT block, and then transmitted through the channel;

4) The receiving end extracts the pilot frequency at the front end of the data block from the received TFU-SCM symbol block, and performs symbol synchronization and frequency synchronization;

5) After symbol synchronization and carrier synchronization are completed, use the pilot frequency to estimate the frequency domain gain of each frequency point of the channel when the corresponding TFU-SCM symbol block passes through the channel;

6) delete the pilot frequency of the front end in each TFU-SCM symbol block, obtain each FFT block;

7) performing Fourier transform on the FFT block to obtain a frequency-domain signal corresponding to the time-domain FFT block;

8) performing an equalization operation on the frequency domain signal by using the frequency domain gain in (5), to obtain an equalized frequency domain signal;

9) performing an IFFT operation on the frequency domain signal after the equalization operation, removing the UW at the back end of each FFT block, and obtaining a restored data block;

10) Constellation inverse mapping and channel decoding are performed sequentially on the recovered data blocks to obtain original information.

The characteristics and advantages of the signal transmission method using time-frequency domain combined single-carrier modulation proposed by the present invention are:

The present invention refers to this technology as time domain and 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 special word (UniqueWord, 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) constitutes a TFU-SCM symbol, and by operating the pilot in the frequency domain, operations such as synchronization, channel estimation, and equalization can be conveniently performed at the receiving end.

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. and other issues such as channel fading.

The present invention can flexibly select the number of UWs in the pilot according to the requirements of system performance, and can conveniently perform operations such as synchronization, channel estimation and equalization at the receiving end through the operation of the pilot in the frequency domain. 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 flow diagram of the existing OFDM technology.

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

FIG. 3 is a schematic diagram of an SC-FDE frame structure in an 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:

A kind of signal transmission method that adopts the single carrier modulation of time-frequency domain combination that the present invention proposes, it is characterized in that, this method comprises the following steps:

1) Perform channel coding and constellation mapping on the information generated by the transmitting end in sequence to obtain multiple symbols after mapping;

2) Composing a plurality of symbols after the above mapping into a data block;

3) TFU-SCM modulation is performed on each data block: set UW as a reference sequence; insert a pilot composed of one or more UWs at the front end of the data block, and insert a UW at the back end as a guard interval, and the data The block and the back-end UW form an FFT block, and a time-frequency domain combined single-carrier modulation symbol (TFU-SCM symbol for short) block is formed by the pilot block and the FFT block, and then transmitted through the channel;

4) The receiving end extracts the pilot frequency at the front end of the data block from the received TFU-SCM symbol block, and performs symbol synchronization and frequency synchronization;

5) After symbol synchronization and carrier synchronization are completed, use the pilot frequency to estimate the frequency domain gain of each frequency point of the channel when the corresponding TFU-SCM symbol block passes through the channel;

6) delete the pilot frequency of the front end in each TFU-SCM symbol block, obtain each FFT block;

7) performing Fourier transform on the FFT block to obtain a frequency-domain signal corresponding to the time-domain FFT block;

8) performing an equalization operation on the frequency domain signal by using the frequency domain gain in 5), to obtain an equalized frequency domain signal;

9) performing an IFFT operation on the frequency domain signal after the equalization operation, removing the UW at the back end of each FFT block, and obtaining a restored data block;

10) Constellation inverse mapping and channel decoding are performed sequentially on the recovered data blocks to obtain original information.

The structure of the above 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 The FFT block composed of a UW in the back.

An embodiment of a signal transmission method using time-frequency domain joint single-carrier modulation proposed by the present invention, as shown in Figures 5 and 6, includes the following steps:

1) Perform channel coding and constellation mapping on the information to be sent by the sending end in sequence, and obtain multiple symbols after mapping;

The channel coding manner may be a convolutional code (Convolutional Code, CC), a low density parity check code (Low Density Parity Check, LDPC), a Reed-Solomon code (Reed Solomon, RS) and so on.

Constellation mapping is performed on the information after channel coding, and 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) forming a plurality of symbols after the above mapping into a parallel data block;

3) Perform TFU-SCM modulation on each data block: set UW as a reference sequence; insert multiple symbol pilots composed of one or more UWs at the front end of the above data block, and insert a UW at the back end, the data block It forms an FFT block with the back-end UW, and after the pilot block and the FFT block form a time-frequency domain joint single-carrier modulation (TFU-SCM) symbol block (as shown in the virtual box in Figure 5), each TFU-SCM The symbol blocks are composed into a frame signal and sent through the channel. The specific TFU-SCM symbol block generation process is as follows:

3-1) Generate a UW sequence. In this embodiment, the UW selects the Chu sequence (proposed by David C.Chu) or the Frank-Zadoff sequence (proposed jointly by R.L.Frank and S.A.Zadoff) as the UW sequence, and its length is a positive integer of 2 Power, 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 in this embodiment 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 that the length is U (U is a positive integer) are generated by the following formula respectively (:

I[n]=cos(θ[n]) (1)

Q[n]=sin(θ[n]) (2)

Where n is any integer within 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:

${\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; Frank</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; q</span>}\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;pqr</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\sqrt{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Where r=1,3 or with integers that are relatively prime;

The expression of θ _Chu [n] is:

${\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; chu</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;n</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

n=0,1,...,U-1 (7)

3-2) inserting a UW at the rear end of each of the above-mentioned parallel data blocks as a guard interval, and the data block and UW form an FFT block;

3-3) Insert a pilot block consisting of one or more UWs at the front end of the FFT block (the higher the system performance requirements, the more UWs in the pilot block, but the number of UWs does not exceed 4), and the Frequency blocks and FFT blocks form a TFU-SCM symbol, as shown in Figure 4;

4) The receiving end receives the frame signal composed of the above-mentioned TFU-SCM symbols, and splits the received frame signal into multiple parallel TFU-SCM symbols according to the corresponding composition method, and joint single-carrier modulation from the time-frequency domain The symbol block extracts the pilot frequency at the front end of the data block, and performs symbol synchronization and frequency synchronization;

5) After symbol synchronization and carrier synchronization are completed, the above-mentioned pilot frequency is used to estimate the frequency-domain gain of each frequency point of the channel when the corresponding time-frequency domain joint single-carrier modulation symbol block passes through the channel; the channel estimation in this embodiment adopts the method based on discrete Fourier transform (Discrete Fourier Transform, hereinafter referred to as DFT) channel estimation algorithm.

The DFT channel estimation algorithm is as follows:

In this embodiment, 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), and {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 Any integer in the range of 0 to L-1) representation. 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:

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

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.

6) According to the obtained symbol synchronization information, the pilot frequency in each TFU-SCM symbol is separated from the FFT block, and the pilot frequency of the front end in the combined single-carrier modulation symbol block of each time-frequency domain is deleted to obtain each FFT block;

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

8) using the frequency domain gain in 5) to perform an equalization operation on the frequency domain signal to obtain an equalized frequency domain signal;

The channel equalization adopts a Zero Forcing (ZF for short) equalization algorithm.

The ZF equalization algorithm is as follows:

The basic method of ZF is that the sending end sends a training sequence, which corresponds to an ideal acceptance value. After the training sequence is interfered by the ISI channel, the disturbed value is obtained at the receiving end, and then the ideal value is compared with the disturbed value to filter The equalization coefficient of the filter, from the frequency domain point of view, is to multiply the frequency response of the disturbed signal by a frequency response function (the frequency response of the adaptive filter), so that it is equal to the frequency response of the ideal received signal.

The equalization coefficient is expressed as:

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

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

9) Perform an IFFT operation on the above equalized frequency domain signal, remove the UW at the back end of each data block, and obtain the restored data block. After the above-mentioned single-carrier demodulation process of time-frequency domain joint for each channel of TFU-SCM symbols, multiple channels of parallel data blocks are combined into serial data. The single-carrier demodulation is shown in the dashed box in Figure 6 (steps 4-9);

10) Constellation inverse mapping and channel decoding are performed sequentially on the recovered data blocks to obtain original information. The constellation inverse mapping and channel decoding are performed according to the constellation mapping and channel coding methods corresponding to the sending 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 channel coding and constellation mapping on the information to be sent by the sending end in sequence, and obtain multiple symbols after mapping; 2) a plurality of symbols after the above-mentioned mapping are formed into a parallel data block; 3) Perform TFU-SCM modulation on each data block: set UW as a reference sequence; insert a pilot composed of several UWs at the front end of the above data block, and insert a UW at the back end, the data block and the UW at the back end consist of The FFT block is composed of the pilot block and the FFT block to form a time-frequency domain joint single-carrier modulation symbol block, and the TFU-SCM symbol blocks of each channel are composed into a frame signal and then sent through the channel; 4) The receiving end extracts the pilot frequency at the front end of the data block from the received time-frequency domain joint single-carrier modulation symbol block, and performs symbol synchronization and frequency synchronization; 5) After symbol synchronization and carrier synchronization are completed, use the pilot to estimate the frequency domain gain of each frequency point of the channel when the corresponding time-frequency domain joint single-carrier modulation symbol block passes through the channel; 6) deleting the pilot frequency of the front end in the combined single-carrier modulation symbol block of each time-frequency domain to obtain each FFT block; 7) performing Fourier transform on the FFT block to obtain a frequency-domain signal corresponding to the time-domain FFT block; 8) performing an equalization operation on the above-mentioned frequency-domain signal by using the frequency-domain gain in (5), to obtain an equalized frequency-domain signal; 9) Perform an IFFT operation on the equalized frequency domain signal, remove the UW at the back end of each data block, and obtain the restored data block; 10) Constellation inverse mapping and channel decoding are performed sequentially on the recovered data blocks to obtain original information.