阅读说明：本技术 一种基于匹配滤波的多普勒分集接收方法及装置 (Doppler diversity receiving method and device based on matched filtering ) 是由 曾嵘 邵智敏 杭潇 易志强 于 2021-06-08 设计创作，主要内容包括：本发明公开了一种基于匹配滤波的多普勒分集接收方法及装置,本发明方法包括：步骤1：在多天线系统中,基站对发送信号进行预编码,并进行过采样操作；步骤2：接收信号进入简化的多普勒分集接收结构,然后移动台对接收信号进行不同的频移处理得到分集支路上的信号；步骤3：将频移后不同支路上的接收信号分别进行匹配滤波的预处理,将信号去采样；步骤4：采用最大比合并方式对不同支路进行加权合并,通过串并转换后作FFT变换,通过并串转换得到输出信号；步骤5：经过简化的多普勒分集接收结构后,移动台通过估计得到的信道参数对输出信号进行解码操作,并进行判决输出。本发明降低了多普勒扩展带来的性能损失,提高了系统性能。(The invention discloses a Doppler diversity receiving method and a device based on matched filtering, and the method comprises the following steps: step 1: in a multi-antenna system, a base station performs precoding on a transmission signal and performs oversampling operation; step 2: the received signal enters a simplified Doppler diversity receiving structure, and then the mobile station carries out different frequency shift processing on the received signal to obtain a signal on a diversity branch; and step 3: respectively carrying out preprocessing of matched filtering on the received signals on different branches after frequency shift, and carrying out signal sampling removal; and 4, step 4: carrying out weighting combination on different branches by adopting a maximum ratio combination mode, carrying out FFT (fast Fourier transform) after serial-to-parallel conversion, and obtaining output signals through parallel-to-serial conversion; and 5: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output. The invention reduces the performance loss caused by Doppler expansion and improves the system performance.)

1. A Doppler diversity receiving method based on matched filtering is characterized by comprising the following steps:

step 1: in a multi-antenna system, a base station performs precoding on a transmission signal and performs oversampling operation;

step 2: the received signal enters a simplified Doppler diversity receiving structure, and then the mobile station carries out different frequency shift processing on the received signal to obtain a signal on a diversity branch;

and step 3: respectively carrying out preprocessing of matched filtering on the received signals on different branches after frequency shift, and carrying out signal sampling removal;

and 4, step 4: carrying out weighting combination on different branches by adopting a maximum ratio combination mode, carrying out FFT (fast Fourier transform) after serial-to-parallel conversion, and obtaining output signals through parallel-to-serial conversion;

and 5: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output.

2. The matched filtering based doppler diversity reception method as claimed in claim 1, wherein:

the step 1 is as follows: m base stations carry out precoding on the transmitted signals and carry out oversampling operation, wherein the sampling rate is alpha; let the received signal in the mobile station be x (n) assuming that the synchronization position of the receiver is aligned with the signal received from the first base station.

3. The matched filtering based doppler diversity reception method as claimed in claim 2, wherein: the step 2 is as follows: the mobile station first makes a decision on the received signalThe ith signal after different frequency shifts is represented as

Wherein N is more than or equal to 0 and less than or equal to N-1, i is more than or equal to 0 and less than or equal to N-1,is an estimated Doppler frequency shift value, x (n) represents the received signal in the time domain, x_i(n) is x (n) frequency shiftThe latter signal, N representing the number of data symbols, T_sRepresenting the signal sampling interval, j is the unit of an imaginary number.

4. A matched filtering based doppler diversity reception method as claimed in claim 3, wherein: the step 3 is as follows: processing the signal by a root raised cosine filter to correct signal interference caused by intersymbol interference ISI, and then sampling the signal;

wherein the root raised cosine filter has a transfer function of

Wherein R represents the magnitude of the roll-off coefficient, T_sRepresents the signal sampling interval in seconds;

the received signals with different frequency shifts are processed by matched filtering, namely the signals are convoluted with the transmission function of a filter, and the obtained signals are the signals

y_i(n)＝x_i(n)*h(n)。

5. The matched filtering based doppler diversity reception method of claim 4, wherein: the step 4 is as follows:

the weighting coefficient of the kth (k ═ 1,2, …, M) branch is

Wherein the content of the first and second substances,representing the interference signal in the ith subcarrier frequency domain.

When maximum ratio combination is carried out, each frequency offset moving branch takes conjugation of the estimated channel parameters to obtain each branch weighting coefficient of the ith subcarrier signal as

Wherein k is more than or equal to 1 and less than or equal to M, M is the number of branches, H represents the channel gain,p represents the interference power of the branch after the frequency spectrum is shifted;

the ith combined subcarrier signal is represented as

Wherein, w_k,iBranch weighting factor, y, representing the ith subcarrier signal_kAnd (n) represents signals of different branches after matched filtering processing.

6. A Doppler diversity receiving device based on matched filtering is characterized by comprising the following modules:

a pre-coding module: in a multi-antenna system, a base station performs precoding on a transmission signal and performs oversampling operation;

the frequency shift processing module: the received signal enters a simplified Doppler diversity receiving structure, and then the mobile station carries out different frequency shift processing on the received signal to obtain a signal on a diversity branch;

the matched filtering preprocessing module: respectively carrying out preprocessing of matched filtering on the received signals on different branches after frequency shift, and carrying out signal sampling removal;

a weighting module: carrying out weighting combination on different branches by adopting a maximum ratio combination mode, carrying out FFT (fast Fourier transform) after serial-to-parallel conversion, and obtaining output signals through parallel-to-serial conversion;

a decoding and output module: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output.

7. The matched filtering based doppler diversity receiving apparatus of claim 6, wherein:

the pre-coding module specifically comprises the following steps: m base stations carry out precoding on the transmitted signals and carry out oversampling operation, wherein the sampling rate is alpha; let the received signal in the mobile station be x (n) assuming that the synchronization position of the receiver is aligned with the signal received from the first base station.

8. The matched filtering based doppler diversity receiving apparatus of claim 7, wherein: the frequency shift processing module specifically comprises the following modules: the mobile station first makes a decision on the received signalThe ith signal after different frequency shifts is represented as

Wherein N is more than or equal to 0 and less than or equal to N-1, i is more than or equal to 0 and less than or equal to N-1,is an estimated Doppler frequency shift value, x (n) represents the received signal in the time domain, x_i(n) is x (n) frequency shiftIn the latter signal, N represents the number of data symbols.

9. The matched filtering based doppler diversity receiving apparatus of claim 8, wherein: the matched filtering preprocessing module is specifically as follows: processing the signal by a root raised cosine filter to correct signal interference caused by intersymbol interference ISI, and then sampling the signal;

wherein the root raised cosine filter has a transfer function of

Wherein R represents the magnitude of the roll-off coefficient, T_sRepresents the signal sampling interval in seconds;

the received signals with different frequency shifts are processed by matched filtering, namely the signals are convoluted with the transmission function of a filter, and the obtained signals are the signals

y_i(n)＝x_i(n)*h(n)。

10. The matched filtering based doppler diversity receiving apparatus of claim 9, wherein: the weighting module specifically comprises the following components:

the weighting coefficient of the kth (k ═ 1,2, …, M) branch is

Wherein the content of the first and second substances,representing the interference signal in the ith subcarrier frequency domain.

When maximum ratio combination is carried out, each frequency offset moving branch takes conjugation of the estimated channel parameters to obtain each branch weighting coefficient of the ith subcarrier signal as

Wherein k is more than or equal to 1 and less than or equal to M, M is the number of branches, H represents the channel gain,p represents the interference power of the branch after the frequency spectrum is shifted;

the ith combined subcarrier signal is represented as

Wherein, w_k,iBranch weighting factor, y, representing the ith subcarrier signal_kAnd (n) represents signals of different branches after matched filtering processing.

Technical Field

The invention belongs to the technical field of design of a receiving system in a high-speed mobile environment, and particularly relates to a Doppler diversity receiving method and device based on matched filtering.

Background

In a high-speed mobile communication system, the doppler effect caused by the high mobility of the vehicle can greatly reduce the signal detection quality of the system, thereby seriously affecting the transmission reliability of the communication system. Because the performance of the system is seriously degraded due to the influence of the doppler shift, a receiving end needs to perform frequency offset estimation and compensation on a signal before decoding, and the influence of the doppler effect can be resisted by a method for estimating and compensating the doppler shift. Generally, frequency offset in a communication system is mainly generated by the following factors: phase Noise (PN), carrier frequency offset, and doppler shift. For the above factors, methods such as training sequence can be used for estimation and compensation, but because the frequency spreading of doppler frequency shift has a relationship with the receiving antenna and channel environment, the compensation method can only reduce the influence on the system, but cannot completely eliminate the influence, and doppler diversity regards doppler spreading as a diversity method, whose basic principle is to obtain diversity gain by using doppler frequency shift. The doppler shift can be regarded as a delay of the frequency domain in the frequency domain, and the doppler diversity can be regarded as an important diversity resource, which is processed with the original signal in a series to enhance the transmission signal, so that the doppler effect is resisted, the signal-to-noise ratio performance is enhanced, and the system performance is improved.

In addition, in a high-speed mobile scenario, time-varying channel fading is one of the most serious problems affecting the performance of the communication system, and the transmission performance of the communication system can be effectively improved by using a spatial diversity technique. However, in the conventional doppler diversity receiving structure, the system obtains diversity gain by shifting the frequency spectrum of the received signal, and this method cannot fully and effectively utilize the diversity resources caused by the frequency offset, and has a certain performance limit.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a Doppler diversity receiving method and device based on matched filtering, which simplify the diversity receiving structure, carry out frequency shift and filtering on signals in a matched filtering preprocessing mode, further reduce the performance loss caused by Doppler expansion, thus obtaining more diversity gain and improving the system performance. In order to achieve the purpose, the invention adopts the following technical scheme:

a Doppler diversity receiving method based on matched filtering comprises the following steps:

step 1: in a multi-antenna system, a base station performs precoding on a transmission signal and performs oversampling operation;

step 2: the received signal enters a simplified Doppler diversity receiving structure, and then the mobile station carries out different frequency shift processing on the received signal to obtain a signal on a diversity branch;

and step 3: respectively carrying out preprocessing of matched filtering on the received signals on different branches after frequency shift, and then carrying out signal sampling removal;

and 4, step 4: weighting and combining different branches by adopting a Maximum Ratio Combining (MRC) mode, performing FFT (fast Fourier transform) after serial-to-parallel conversion, and finally obtaining an output signal through parallel-to-serial conversion;

and 5: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output.

Preferably, step 1: the M base stations firstly carry out precoding on the transmitted signals and carry out oversampling operation, wherein the sampling rate is alpha. Let the received signal in the mobile station be x (n) assuming that the synchronization position of the receiver is aligned with the signal received from the first base station.

Preferably, step 2: the received signal enters a simplified doppler diversity reception architecture. The mobile station first makes a decision on the received signalThe ith signal after different frequency shifts can be represented as

Wherein N is more than or equal to 0 and less than or equal to N-1, i is more than or equal to 0 and less than or equal to N-1,is an estimated Doppler frequency shift value, x (n) represents the received signal in the time domain, x_i(n) is x (n) frequency shiftThe latter signal, N representing the number of data symbols, T_sRepresenting the signal sampling interval, j is the unit of an imaginary number.

Preferably, step 3: the frequency-shifted received signals are respectively preprocessed by matched filtering, the matched filtering adopts an rrc (root raised cosine filter), the signals are processed by the rrc (root raised cosine filter) to correct signal interference caused by ISI (intersymbol interference), and then the signals are subjected to de-sampling.

Wherein the root raised cosine filter has a transfer function of

Wherein R represents the magnitude of the roll-off coefficient, T_sRepresenting the signal sampling interval in seconds.

The received signals with different frequency shifts are processed by matched filtering, namely the signals are convoluted with the transmission function of a filter, and the obtained signals are the signals

y_i(n)＝x_i(n)*h(n)。

Preferably, step 4: the weighting coefficient of the kth (k ═ 1,2, …, M) branch is

Wherein the content of the first and second substances,representing the interference signal in the ith subcarrier frequency domain.

When maximum ratio combination is carried out, each frequency offset moving branch takes conjugation of the estimated channel parameters to obtain each branch weighting coefficient of the ith subcarrier signal as

Wherein k is more than or equal to 1 and less than or equal to M, M is the number of branches, H represents the channel gain,p represents the interference power of the branch after the frequency spectrum shift.

The ith combined subcarrier signal is represented as

Wherein, w_k,iBranch weighting factor, y, representing the ith subcarrier signal_kAnd (n) represents signals of different branches after matched filtering processing.

The invention also discloses a Doppler diversity receiving device based on matched filtering, which comprises the following modules:

a pre-coding module: in a multi-antenna system, a base station performs precoding on a transmission signal and performs oversampling operation;

the frequency shift processing module: the received signal enters a simplified Doppler diversity receiving structure, and then the mobile station carries out different frequency shift processing on the received signal to obtain a signal on a diversity branch;

the matched filtering preprocessing module: respectively carrying out preprocessing of matched filtering on the received signals on different branches after frequency shift, and carrying out signal sampling removal;

a weighting module: carrying out weighting combination on different branches by adopting a maximum ratio combination mode, carrying out FFT (fast Fourier transform) after serial-to-parallel conversion, and obtaining output signals through parallel-to-serial conversion;

a decoding and output module: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output.

Preferably, the pre-coding module specifically includes: m base stations carry out precoding on the transmitted signals and carry out oversampling operation, wherein the sampling rate is alpha; let the received signal in the mobile station be x (n) assuming that the synchronization position of the receiver is aligned with the signal received from the first base station.

Preferably, the frequency shift processing module specifically includes: the mobile station first makes a decision on the received signalThe ith signal after different frequency shifts is represented as

Wherein N is more than or equal to 0 and less than or equal to N-1, i is more than or equal to 0 and less than or equal to N-1,is an estimated Doppler frequency shift value, x (n) represents the received signal in the time domain, x_i(n) is x (n) frequency shiftIn the latter signal, N represents the number of data symbols.

Preferably, the matched filtering preprocessing module specifically includes: processing the signal by a root raised cosine filter to correct signal interference caused by ISI (intersymbol interference), and then, sampling the signal;

wherein the root raised cosine filter has a transfer function of

Wherein R represents the magnitude of the roll-off coefficient, T_sRepresents the signal sampling interval in seconds;

the received signals with different frequency shifts are processed by matched filtering, namely the signals are convoluted with the transmission function of a filter, and the obtained signals are the signals

y_i(n)＝x_i(n)*h(n)。

Preferably, the weighting module specifically includes:

the weighting coefficient of the kth (k ═ 1,2, …, M) branch is

Wherein the content of the first and second substances,representing the interference signal in the ith subcarrier frequency domain.

When maximum ratio combination is carried out, each frequency offset moving branch takes conjugation of the estimated channel parameters to obtain each branch weighting coefficient of the ith subcarrier signal as

Wherein k is more than or equal to 1 and less than or equal to M, M is the number of branches, H represents the channel gain,p represents the interference power of the branch after the frequency spectrum is shifted;

the ith combined subcarrier signal is represented as

Wherein, w_k,iBranch weighting factor, y, representing the ith subcarrier signal_kAnd (n) represents signals of different branches after matched filtering processing.

The invention has the following beneficial effects:

(1) the invention processes the received signal by using the Doppler diversity receiving scheme, simplifies the diversity structure, further reduces the performance loss caused by Doppler expansion by adopting a matched filtering pretreatment mode, obtains more diversity gains and improves the system performance.

(2) The invention combines the simplified diversity structure into the system, reduces the calculation times and improves the efficiency of signal processing on the basis of ensuring the performance of the original system. Therefore, the method can show better feasibility when being applied to a practical communication system.

Drawings

Fig. 1 is a flow chart of a doppler diversity receiving method based on matched filtering according to the present invention.

Fig. 2 is a diagram of a doppler diversity reception structure.

Fig. 3 is a block diagram of a doppler diversity receiving apparatus based on matched filtering according to the present invention.

Detailed Description

The following preferred examples are provided to further illustrate the technical solutions provided by the present invention, but should not be construed as limiting the invention.

As shown in fig. 1-2, the doppler diversity receiving method based on matched filtering of the present invention specifically includes the following steps:

step 1: the M base stations firstly carry out precoding on the transmitted signals and carry out oversampling operation, wherein the sampling rate is alpha. Let the received signal in the mobile station be x (n) assuming that the synchronization position of the receiver is aligned with the signal received from the first base station.

Step 2: the received signal enters a simplified doppler diversity reception architecture. The mobile station first makes a decision on the received signalThe ith signal after different frequency shifts can be represented as

Wherein N is more than or equal to 0 and less than or equal to N-1, i is more than or equal to 0 and less than or equal to N-1,is an estimated Doppler frequency shift value, x (n) represents the received signal in the time domain, x_i(n) is x (n) frequency shiftIn the latter signal, N represents the number of data symbols.

And step 3: and respectively preprocessing the frequency-shifted received signals by matched filtering, wherein the matched filtering adopts an rrc (root raised cosine filter), the signals are processed by the rrc (root raised cosine filter) to correct signal interference caused by ISI, and finally, the signals are subjected to de-sampling.

Wherein the root raised cosine filter has a transfer function of

Wherein R represents the magnitude of the roll-off coefficient, T_sRepresenting the signal sampling interval in seconds.

The received signals with different frequency shifts are processed by matched filtering, namely the signals are convoluted with the transmission function of a filter, and the obtained signals are the signals

y_i(n)＝x_i(n)*h(n)。

And 4, step 4: and weighting and combining different branches by adopting a Maximum Ratio Combining (MRC) mode, performing FFT (fast Fourier transform) after serial-to-parallel conversion, and finally obtaining an output signal through parallel-to-serial conversion.

The weighting coefficient of the kth (k ═ 1,2, …, M) branch is

Wherein the content of the first and second substances,representing the interference signal in the ith subcarrier frequency domain.

When maximum ratio combination is carried out, each frequency offset moving branch takes conjugation of the estimated channel parameters to obtain each branch weighting coefficient of the ith subcarrier signal as

Wherein k is more than or equal to 1 and less than or equal to M, M is the number of branches, H represents the channel gain,p represents the interference power of the branch after the frequency spectrum shift.

The ith combined subcarrier signal is represented as

Wherein, w_k,iBranch weighting factor, y, representing the ith subcarrier signal_kAnd (n) represents signals of different branches after matched filtering processing.

And 5: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output.

As shown in fig. 3, the doppler diversity receiving apparatus based on matched filtering of the present invention specifically includes the following modules:

a pre-coding module: the M base stations firstly carry out precoding on the transmitted signals and carry out oversampling operation, wherein the sampling rate is alpha. Let the received signal in the mobile station be x (n) assuming that the synchronization position of the receiver is aligned with the signal received from the first base station.

The frequency shift processing module: the received signal enters a simplified doppler diversity reception architecture. The mobile station first makes a decision on the received signalThe ith signal after different frequency shifts can be represented as

Wherein N is more than or equal to 0 and less than or equal to N-1, i is more than or equal to 0 and less than or equal to N-1,is an estimated Doppler frequency shift value, x (n) represents the received signal in the time domain, x_i(n) is x (n) frequency shiftIn the latter signal, N represents the number of data symbols.

The matched filtering preprocessing module: and respectively preprocessing the frequency-shifted received signals by matched filtering, wherein the matched filtering adopts an rrc (root raised cosine filter), the signals are processed by the rrc (root raised cosine filter) to correct signal interference caused by ISI, and finally, the signals are subjected to de-sampling.

Wherein the root raised cosine filter has a transfer function of

Wherein R represents the magnitude of the roll-off coefficient, T_sRepresenting the signal sampling interval in seconds.

The received signals with different frequency shifts are processed by matched filtering, namely the signals are convoluted with the transmission function of a filter, and the obtained signals are the signals

y_i(n)＝x_i(n)*h(n)。

A weighting module: and weighting and combining different branches by adopting a Maximum Ratio Combining (MRC) mode, performing FFT (fast Fourier transform) after serial-to-parallel conversion, and finally obtaining an output signal through parallel-to-serial conversion.

The weighting coefficient of the kth (k ═ 1,2, …, M) branch is

Wherein the content of the first and second substances,representing the interference signal in the ith subcarrier frequency domain.

When maximum ratio combination is carried out, each frequency offset moving branch takes conjugation of the estimated channel parameters to obtain each branch weighting coefficient of the ith subcarrier signal as

Wherein k is more than or equal to 1 and less than or equal to M, M is the number of branches, H represents the channel gain,p represents the interference power of the branch after the frequency spectrum shift.

The ith combined subcarrier signal is represented as

Wherein, w_k,iBranch weighting factor, y, representing the ith subcarrier signal_kAnd (n) represents signals of different branches after matched filtering processing.

A decoding and output module: after the simplified Doppler diversity receiving structure, the mobile station performs decoding operation on the output signal through the estimated channel parameters, and performs decision output.

The Doppler diversity receiving method and device based on the matched filtering preprocess the received signals in a matched filtering mode, obtain diversity gain to the maximum extent and further reduce performance loss caused by Doppler expansion.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core ideas. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.