CN112187338B - Two-stage processing interference cancellation system and method for asynchronous CDMA system - Google Patents

Abstract

The invention discloses a two-stage processing interference cancellation system for an asynchronous code division multiple access system, which belongs to the technical field of signal processing and comprises a beam synthesis module, a spread spectrum code capturing module, a multi-channel high-power signal demodulator module, a signal regeneration reconstruction module, a delay module, a multi-target interference cancellation module, a multi-channel low-power signal demodulator module and a channel decoding module. The invention can improve the capacity of the asynchronous code division multiple access system, reduce the complexity of hardware realization and is easy to realize engineering; the problem that the high-power signal in the asynchronous code division multiple access system suppresses the low-power signal to enable the low-power signal not to be captured and demodulated can be solved, the performance of the asynchronous code division multiple access system is improved, and the asynchronous code division multiple access system is worthy of being popularized and used.

Description

A two-stage processing interference cancellation system and method for an asynchronous code division multiple access system

technical field

The invention relates to the technical field of signal processing, in particular to a two-stage processing interference cancellation system and method for an asynchronous code division multiple access system.

Background technique

In a code division multiple access system, there is a certain correlation between the signals of each user, which is the root cause of the existence of multiple access interference (MAI). Compared with terrestrial communication, the large link transmission delay in satellite communication makes closed-loop power control impossible in satellite communication systems.

With the increase of the number of low-orbit spacecraft, there will be multiple users in a beam in the future. The traditional detection technology directly performs spreading code matching processing on the signal of each user according to the direct spreading sequence theory, so the anti-MAI ability is poor. When the dynamic range of the user level is large, the high-power signal suppresses the low-power signal, so that the low-power signal cannot be captured and detected. The above problems need to be solved urgently. To this end, an asynchronous code division multiple access system with two-stage processing interference cancellation system is proposed.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: how to solve the problem that the high-power signal suppresses the low-power signal in the asynchronous code division multiple access system, so that the low-power signal cannot be captured, demodulated and decoded, and an asynchronous code division multiple access system is provided. Two-stage processing interference cancellation system.

The present invention solves the above technical problems through the following technical solutions. The present invention includes a beam forming module, a spread spectrum code acquisition module, a multi-channel high-power signal demodulator module, a signal regeneration and reconstruction module, a delay module, and a multi-target interference cancellation module. module, multi-channel low-power signal demodulator module, channel decoding module;

The beam forming module is used for weighting processing of the input multi-channel baseband array signal to perform digital beam forming;

The spread spectrum code capture module is used to capture the signal and find the starting moment of the data code phase;

The multi-channel high-power signal demodulator module is used to demodulate the spread spectrum signals of multiple high-power users at the same time;

The signal regeneration and reconstruction module is used for reconstructing and regenerating the high-power interference signal;

The delay module is used to delay the original baseband array signal input to the multi-channel high-power signal demodulator module;

The multi-target interference cancellation module is used to deduct the regenerated high-power interference signal from the baseband array signal after the original beam synthesis;

The multi-channel low-power signal demodulator module is used to demodulate multiple low-power user spread spectrum signals at the same time;

The channel decoding module is used to decode the spread spectrum signal of the low-power user after demodulation, and output the data before encoding;

the beam forming module, the multi-channel high-power signal demodulator module, the signal regeneration and reconstruction module, the multi-target interference cancellation module, the multi-channel low-power signal demodulator module, the channel The decoding modules are connected in sequence, the spread spectrum code acquisition module is connected with the multi-channel high-power signal demodulator module, and the delay module is respectively connected with the beam forming module and the multi-target interference cancellation module.

Further, the spread spectrum code acquisition module utilizes the cross-correlation characteristic of the Gold sequence to construct a composite code as a local pseudocode, and performs parallel search on the code phase-carrier frequency offset two-dimensional plane to determine the difference between the received signal and the local pseudocode. The code phase and carrier frequency offset of a certain set of code phase and carrier frequency offset, specifically, the local code is set to different code phase and carrier frequency offset to correlate with the received signal. When the value peaks, the group is set as the result of code acquisition, and the presence of signals of multiple users can be detected in parallel by implementing one of the spread spectrum code acquisition modules.

Further, the spread spectrum code acquisition module includes a matched filter, and the matched filter is a two-dimensional matched filter, which is used for simultaneous searching in the time domain and frequency domain, thereby improving the ability to acquire parallel search.

Further, the structure of the multi-channel high-power signal demodulator and the multi-channel low-power signal demodulator module is the same, and both include a carrier and code dynamic cancellation module, a despreading and integrating module, and a synchronization loop. The carrier and code dynamic cancellation module is connected to the beam forming module, the carrier and code dynamic cancellation module, the despread and integration module, and the synchronization loop are connected in sequence, and the synchronization loop is connected to the signal regeneration and reconstruction Module connection.

Further, the carrier and code dynamic cancellation module performs Doppler compensation of the carrier and the PN code on the input baseband signal to offset the dynamics of the carrier frequency and the PN code rate in the baseband signal; the despreading and integrating module strips the receiving PN code in the baseband signal, and perform integration operation on the despread baseband signal according to the symbol period before channel decoding; the synchronization loop outputs the synchronization information to the carrier and code dynamic cancellation module to form a closed-loop loop , and simultaneously output synchronization information to the signal regeneration and reconstruction module to regenerate high-power interference signals.

Further, the signal regeneration and reconstruction module includes a plurality of channels of parallel signal regeneration units, and the signal regeneration unit is configured to utilize the synchronization information and the symbol decision value output by the multi-channel high-power signal demodulator module. Multi-user detection technology reconstructs and regenerates high-power interference signals.

Further, in the delay module, the delay amount of the original baseband array signal input to the multi-channel high-power signal demodulator module is the sum of the processing delay of the multi-channel high-power signal demodulator module and the signal regeneration delay. .

Further, the multi-target interference cancellation module includes a multi-channel adder and a subtractor, the output end of the multi-channel adder is connected with the input end of the subtracter, and the input ends of the multi-channel adder are respectively It is connected to each of the signal regeneration units, and the output end of the subtractor is connected to the carrier and code dynamic cancellation module in the multi-channel low-power signal demodulator.

Further, the input end of the subtractor is connected to the delay module.

The present invention also provides a two-stage processing interference cancellation method for an asynchronous code division multiple access system, comprising the following steps:

S1: Capture and demodulate the high-power signal to recover the high-power signal;

S2: deduct the high-power signal in the original beamforming signal;

S3: Demodulate and decode the low-power signal.

Compared with the prior art, the present invention has the following advantages: the asynchronous code division multiple access system uses a two-stage processing interference cancellation system, which can improve the capacity of the asynchronous code division multiple access system, reduce the complexity of hardware implementation, and is easy to implement in engineering; In the asynchronous code division multiple access system, the high power signal suppresses the low power signal so that the low power signal cannot be captured and demodulated, which improves the performance of the asynchronous code division multiple access system and is worthy of popularization.

Description of drawings

1 is a schematic flowchart of two-stage processing interference cancellation in Embodiment 1 of the present invention;

2 is a schematic block diagram of the structure of a two-stage processing interference cancellation system in Embodiment 2 of the present invention;

3 is a schematic block diagram of the structure of a spread spectrum code capture module in Embodiment 2 of the present invention;

4 is a schematic structural block diagram of two types of multi-channel demodulator modules in Embodiment 2 of the present invention;

5 is a schematic structural block diagram of a signal regeneration and reconstruction module in Embodiment 2 of the present invention;

FIG. 6 is a schematic structural block diagram of a multi-target interference cancellation module in Embodiment 2 of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following implementation. example.

Example 1

This embodiment provides a technical solution: a two-stage processing interference cancellation system for an asynchronous code division multiple access system, including a beam forming module, a spread spectrum code acquisition module, a multi-channel high-power signal demodulator module, a signal regeneration module structure module, delay module, multi-target interference cancellation module, multi-channel low-power signal demodulator module, channel decoding module;

The beam forming module is used for weighting processing of the input multi-channel baseband array signal to perform digital beam forming;

The spread spectrum code capture module is used to capture the signal and find the starting moment of the data code phase;

The multi-channel high-power signal demodulator module is used to demodulate the spread spectrum signals of multiple high-power users at the same time;

The signal regeneration and reconstruction module is used for reconstructing and regenerating the high-power interference signal;

The delay module is used to delay the original baseband array signal input to the multi-channel high-power signal demodulator module;

The multi-target interference cancellation module is used to deduct the regenerated high-power interference signal from the baseband array signal after the original beam synthesis;

The multi-channel low-power signal demodulator module is used to demodulate multiple low-power user spread spectrum signals at the same time;

The channel decoding module is used to decode the spread spectrum signal of the low-power user after demodulation, and output the data before encoding;

the beam forming module, the multi-channel high-power signal demodulator module, the signal regeneration and reconstruction module, the multi-target interference cancellation module, the multi-channel low-power signal demodulator module, the channel The decoding modules are connected in sequence, the spread spectrum code acquisition module is connected with the multi-channel high-power signal demodulator module, and the delay module is respectively connected with the beam forming module and the multi-target interference cancellation module.

The spread spectrum code acquisition module uses the cross-correlation characteristic of the Gold sequence to construct a composite code as a local pseudo code, and performs parallel search on the code phase-carrier frequency offset two-dimensional plane to determine the code phase and the code phase between the received signal and the local pseudo code. The carrier frequency offset, specifically, is that the local code is set to different code phases and carrier frequency offsets to correlate with the received signal. When a certain group of code phase and carrier frequency offset settings are set, the correlation value between the local code and the received signal has a peak value. , that is, the group is set as the result of code acquisition, and the signal presence of multiple users can be detected in parallel by implementing one of the spread spectrum code acquisition modules.

The spread spectrum code acquisition module includes a matched filter, and the matched filter is a two-dimensional matched filter, which is used for simultaneous searching in the time domain and frequency domain, thereby improving the ability to acquire parallel searching.

The multi-channel high-power signal demodulator has the same structure as the multi-channel low-power signal demodulator module, and both include a carrier and code dynamic cancellation module, a despreading integration module, and a synchronization loop. The carrier and code dynamic The cancellation module is connected to the beam forming module, the carrier and code dynamic cancellation module, the despread and integration module, and the synchronization loop are connected in sequence, and the synchronization loop is connected to the signal regeneration and reconstruction module.

The carrier and code dynamic cancellation module performs Doppler compensation of the carrier and PN code on the input baseband signal, and cancels the dynamics of the carrier frequency and the PN code rate in the baseband signal; the despreading and integration module strips the received baseband signal. PN code, and perform integration operation on the despread baseband signal according to the symbol period before channel decoding; the synchronization loop outputs the synchronization information to the carrier and code dynamic cancellation module, forming a closed loop, and simultaneously outputs the synchronization The information is sent to the signal regeneration and reconstruction module to regenerate the high-power interference signal.

The signal regeneration and reconstruction module includes a plurality of channels of parallel signal regeneration units, and the signal regeneration unit is configured to use the multi-user detection technology according to the synchronization information and the symbol decision value output by the multi-channel high-power signal demodulator module. Reconstruction and regeneration of high-power interference signals.

In the delay module, the delay amount of the original baseband array signal input to the multi-channel high-power signal demodulator module is the sum of the processing delay of the multi-channel high-power signal demodulator module and the signal regeneration delay.

The multi-target interference cancellation module includes a multi-channel adder and a subtracter, the output end of the multi-channel adder is connected with the input end of the subtractor, and the input end of the multi-channel adder is respectively connected with each The signal regeneration unit is connected, and the output end of the subtractor is connected with the carrier and code dynamic cancellation module in the multi-channel low-power signal demodulator.

The input end of the subtractor is connected to the delay module.

As shown in FIG. 1 , this embodiment also provides a two-stage processing interference cancellation method for an asynchronous code division multiple access system, including the following steps:

S1: Capture and demodulate the high-power signal to recover the high-power signal;

S2: deduct the high-power signal in the original beamforming signal;

S3: Demodulate and decode the low-power signal.

Embodiment 2

As shown in FIG. 2 , this embodiment provides a technical solution: an asynchronous code division multiple access system uses a two-stage processing interference cancellation system, which adopts a two-stage processing scheme, and the first-stage processing is first for high-power signals. Capture and demodulate, and then use the signal regeneration and reconstruction module to restore the high-power signal. After deducting the high-power signal from the original beam-synthesized signal, demodulate and decode the obtained low-power signal, mainly including beamforming. module, spread spectrum code acquisition module, multi-channel high-power signal demodulator module, signal regeneration and reconstruction module, delay module, multi-target interference cancellation module, multi-channel low-power signal demodulator module, channel decoding module.

The following describes the relevant information of each module

Beamforming module: used to weight the input multi-channel baseband array signal to perform digital beamforming;

As shown in Figure 3, the spread spectrum code acquisition module: finds the starting moment of the PN code in the received data (that is, the received data code phase), so that the subsequent multi-channel high-power signal demodulator module can initially match the local PN code. Start working in a proper state. In this method, a composite code is constructed as a local pseudocode by using the cross-correlation characteristics of the Gold sequence, and a parallel search is performed on the code phase-carrier frequency offset two-dimensional plane to determine the code phase and carrier frequency between the received signal and the local pseudocode. Specifically, the local code is set to different code phases and carrier frequency offsets to correlate with the received signal. That is, the group is set as the result of code acquisition, so that only one spread spectrum code acquisition module can be used to detect the presence of signals of multiple users in parallel, and quickly detect the signals of users with high power under small resource consumption, which is convenient for The hardware platform with limited processing capability implements multiple access interference detection and cancellation algorithms. However, sharing the same spread spectrum code acquisition module for multiple receiving channels will inevitably affect the speed of code acquisition. Considering this factor in the design, a two-dimensional matched filter that can be searched in both time and frequency domains is used to improve the parallelism of code acquisition. The ability to search significantly reduces code acquisition time with acceptable hardware consumption.

As shown in Figure 4, the multi-channel high-power signal demodulator module: demodulates the spread spectrum signals of multiple high-power users at the same time. composition. The carrier and code dynamic cancellation module performs carrier and PN code Doppler compensation on the input baseband signal to cancel the dynamics of the carrier frequency and PN code rate in the baseband signal; the despreading and integration module is used to strip the PN code in the received baseband signal. , and perform integration operation on the despread baseband signal according to the symbol period before channel decoding; the synchronization loop includes synchronization tracking loops such as carrier synchronization loop, PN code synchronization loop and symbol synchronization loop. The synchronization information output by the synchronization loop On the one hand, it is fed back to the carrier and code dynamic cancellation module to form a closed loop; on the other hand, the synchronization information needs to be transmitted to the signal regeneration and reconstruction module in real time for regenerating high-power interference signals.

As shown in FIG. 5 , the signal regeneration and reconstruction module: the signal regeneration unit uses the multi-user detection (MUD) technology to perform multi-user detection (MUD) technology on the high-power interference signal according to the synchronization information and the symbol decision value output by the multi-channel high-power signal demodulator module. Rebuild regeneration. The signal regeneration and reconstruction module includes signal regeneration units of multiple channels, and can complete the regeneration of multiple high-power interference signals in parallel.

Delay module: delay the baseband array signal input by the original multi-channel high-power signal demodulator module to ensure that the delay of the delayed signal is consistent with the regenerated signal. The delay of the signal is the same as that of the multi-channel high-power signal demodulator module. Processing delay plus signal regeneration delay.

As shown in Figure 6, the multi-target interference cancellation module: deducts the regenerated high-power interference signal from the baseband array signal after the original beam synthesis. According to the simulation analysis, the loss of bit error rate caused by the multiple access interference of low-power users to high-power users is negligible, and only the interference of high-power signals to low-power signals is considered. Therefore, the simplest multi-target interference cancellation module Only one multi-channel adder and one subtractor can be implemented, which greatly reduces the complexity of hardware implementation.

As shown in Figure 4, the multi-channel low-power signal demodulator module: the input is the beam-synthesized baseband array signal after deducting the high-power interference signal, which can demodulate the spread spectrum signals of multiple low-power users at the same time. Channel high power signal demodulator module is the same.

In the channel decoding module: the low-power user signal after demodulation is decoded by the decoding method specified by the transmission system, and the data before encoding is output.

To sum up, the asynchronous code division multiple access system of this embodiment uses a two-stage processing interference cancellation system, which can increase the capacity of the asynchronous code division multiple access system, reduce the complexity of hardware implementation, and facilitate engineering implementation; it can solve the problem of asynchronous code division multiple access. In the multiple access system, the high-power signal suppresses the low-power signal, so that the low-power signal cannot be captured and demodulated, which improves the performance of the asynchronous code division multiple access system and is worthy of popularization.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (3)

1. an asynchronous code division multiple access system uses two-stage processing interference cancellation system, it is characterized in that: comprise beam forming module, spread spectrum code capture module, multi-channel high-power signal demodulator module, signal regeneration reconstruction module, Delay module, multi-target interference cancellation module, multi-channel low-power signal demodulator module, channel decoding module; The beam forming module is used for weighting processing of the input multi-channel baseband array signal to perform digital beam forming; The spread spectrum code acquisition module uses the cross-correlation characteristic of the Gold sequence to construct a composite code as a local pseudo code, and performs parallel search on the code phase-carrier frequency offset two-dimensional plane to determine the code phase and the code phase between the received signal and the local pseudo code. The carrier frequency offset, realizing one of the spread spectrum code acquisition module can detect the signal existence of multiple users in parallel; The multi-channel high-power signal demodulator module is used to demodulate the spread spectrum signals of multiple high-power users at the same time; The multi-channel high-power signal demodulator has the same structure as the multi-channel low-power signal demodulator module, and both include a carrier and code dynamic cancellation module, a despreading integration module, and a synchronization loop. The carrier and code dynamic The cancellation module is connected to the beam forming module, the carrier and code dynamic cancellation module, the despreading integration module, and the synchronization loop are connected in sequence, and the synchronization loop is connected to the signal regeneration and reconstruction module; The signal regeneration and reconstruction module includes a plurality of channels of parallel signal regeneration units, and the signal regeneration unit is configured to use the multi-user detection technology according to the synchronization information and the symbol decision value output by the multi-channel high-power signal demodulator module. Reconstruction and regeneration of high-power interference signals; In the delay module, the original delay amount of the baseband array signal input to the multi-channel high-power signal demodulator module is the sum of the processing delay of the multi-channel high-power signal demodulator module and the signal regeneration delay; The multi-target interference cancellation module includes a multi-channel adder and a subtracter, the output end of the multi-channel adder is connected with the input end of the subtractor, and the input end of the multi-channel adder is respectively connected with each The signal regeneration unit is connected, the output end of the subtractor is connected with the carrier and the code dynamic cancellation module in the multi-channel low-power signal demodulator, and the input end of the subtractor is connected with the delay module; The multi-channel low-power signal demodulator module is used to demodulate multiple low-power user spread spectrum signals at the same time; The channel decoding module is used to decode the spread spectrum signal of the low-power user after demodulation, and output the data before encoding; the beam forming module, the multi-channel high-power signal demodulator module, the signal regeneration and reconstruction module, the multi-target interference cancellation module, the multi-channel low-power signal demodulator module, the channel The decoding modules are connected in sequence, the spread spectrum code acquisition module is connected with the multi-channel high-power signal demodulator module, and the delay module is respectively connected with the beam forming module and the multi-target interference cancellation module; The carrier and code dynamic cancellation module performs Doppler compensation of the carrier and PN code on the input baseband signal, and cancels the dynamics of the carrier frequency and the PN code rate in the baseband signal; the despreading and integration module strips the received baseband signal. PN code, and perform integration operation on the despread baseband signal according to the symbol period before channel decoding; the synchronization loop outputs the synchronization information to the carrier and code dynamic cancellation module, forming a closed loop, and simultaneously outputs the synchronization The information is sent to the signal regeneration and reconstruction module to regenerate the high-power interference signal. 2. a kind of asynchronous code division multiple access system according to claim 1 uses two-stage processing interference cancellation system, it is characterized in that: described spread spectrum code capture module comprises matched filter, and described matched filter is two-dimensional Matched filters for simultaneous searches in the time and frequency domains. 3. an asynchronous code division multiple access system uses two-stage processing interference cancellation method, it is characterized in that, utilize the cancellation system as claimed in claim 1 or 2 to realize receiving processing to high-power signal and low-power signal, including following step: S1: Capture and demodulate the high-power signal to recover the high-power signal; S2: deduct the high-power signal in the original beamforming signal; S3: Demodulate and decode the low-power signal.

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