阅读说明：本技术 一种mc-cdma接收机多径、异址干扰联合抑制方法及系统 (Multi-path and different-address interference combined suppression method and system for MC-CDMA receiver ) 是由 申宇瑶 徐颖 何智力 史雨薇 刘文学 田向伟 罗瑞丹 葛建 于 2019-08-14 设计创作，主要内容包括：本发明提供一种MC-CDMA接收机多径、异址干扰联合抑制方法及系统,通过对多个发射机发射的MC-CDMA信号经多个路径到达接收机的合路信号进行基于迭代最小均方误差准则的开环自适应滤波,实现对由于多径和异址干扰造成的互相关的抑制,获得观测时间内不同延迟处信号复幅度估计,可以实现对多径、异址干扰的互相关旁瓣的抑制；本发明基于不同延迟复幅度相关特性得到三个延迟相关函数,然后对滤波器系数进行了修正；针对MC-CDMA信号模型多载波特性,分别估计每一子载波对应的复幅度,进而针对MC-CDMA信号的符号调制特征,采用模均值作为最后的输出,利用了所有子载波的信息,使得最后输出的复幅度具有更高的信噪比,满足常规扩频通信领域的MC-CDMA接收机抗多径、异址干扰的需求。(The invention provides a multi-path and different-address interference combined suppression method and a system of a MC-CDMA receiver, which can realize the suppression of the cross-correlation caused by the multi-path and different-address interference by carrying out the open-loop adaptive filtering based on the iterative minimum mean square error criterion on the combined signals of the MC-CDMA signals transmitted by a plurality of transmitters and reaching the receiver through a plurality of paths, obtain the complex amplitude estimation of signals at different delays in the observation time and realize the suppression of the cross-correlation side lobe of the multi-path and different-address interference; the method obtains three delay correlation functions based on different delay complex amplitude correlation characteristics, and then corrects the filter coefficient; and aiming at the multi-carrier characteristic of the MC-CDMA signal model, respectively estimating the complex amplitude corresponding to each subcarrier, further aiming at the symbol modulation characteristic of the MC-CDMA signal, adopting a modular mean value as final output, and utilizing the information of all subcarriers, so that the finally output complex amplitude has higher signal-to-noise ratio, and the requirements of the MC-CDMA receiver in the conventional spread spectrum communication field on multipath and different-address interference resistance are met.)

1. A multi-path and different-address interference combined suppressing method for multi-carrier CDMA receiver features that the MC-CDMA signals from K transmitters are received by said receiver at same time, and the number of sub-carriers modulated by MC-CDMA signal is N_cThen the receiver corresponds to K receive channels, characterized by comprising the following steps:

s1: estimating an initial value of the complex amplitude of the nth subcarrier of the kth receiving channel

s2: estimating an initial value from the complex amplitude

s3: based on iterationUsing the three delay correlation functions to calculate the filter coefficient corresponding to each subcarrier of each receiving channel

wherein the content of the first and second substances,

s4: according to the filter coefficientSampling sequence for received signal

s5: the complex amplitude estimation valueThe initial value of the complex amplitude estimation of step S2 is replaced

S6: respectively calculating the final complex amplitude estimated value of different sub-carriers of each receiving channel

2. A multi-path and different-address interference combined suppression system for multi-carrier CDMA receiver features that the MC-CDMA signals from K transmitters are received by receiver at same time, and the number of sub-carriers modulated by MC-CDMA signal is N_cThe receiver corresponds to K receiving channels and is characterized by comprising a complex amplitude initial value setting module, a correlation function calculating module, a filter coefficient calculating module, a filtering module and an average value calculating module;

the complex amplitude initial value setting module is used for estimating an initial value of the nth complex amplitude of the kth receiving channel

the correlation function calculation module is used for estimating an initial value according to the complex amplitude

the filter coefficient calculation module is used for calculating the filter coefficients corresponding to the sub-carriers of each receiving channel respectively by adopting the three delay correlation functions based on the iterative minimum mean square error criterion

wherein the content of the first and second substances,represents a sequence of received signal samples within one spreading code period of the receiver;representing a sequence of spreading code samples corresponding to a subcarrier n of transmitter k within one spreading code period,

the filtering module is used for obtaining the filter coefficient according to the filter coefficient

the correlation function calculation module is further configured to calculate a correlation function based on the complex amplitude estimation value

The mean value calculating module is used for calculating the final complex amplitude estimated value of different subcarriers of each receiving channel

Technical Field

The invention belongs to the field of spread spectrum communication, and particularly relates to a multi-path and different-address interference combined suppression method and system for an MC-CDMA receiver.

Background

Multicarrier code division multiple access (MC-CDMA) signals have the advantages of high spectrum utilization, low subcarrier data rates, and the like, and are widely applied in the field of spread spectrum communications. The MC-CDMA receiver utilizes the orthogonal characteristic of the subcarrier in the MC-CDMA signal and the correlation characteristic of the modulation spread spectrum code to realize the detection and synchronization of the received signal. But its performance is susceptible to multipath and inter-site interference. Under the influence of multipath interference, multipath signals are mutually overlapped, and accurate first path arrival time cannot be acquired; the different-address interference influences the detection and the time delay estimation of the weak target signal.

There are many documents on the problem of inter-site interference or multi-path error suppression, but the problem of interference suppression is rarely studied when the two coexist, and the two influences are considered separately, so that the interference suppression performance is limited.

In the context of "Multistatic adaptive pulse compression" published by Shannon D.Blunt et al in IEEE Transactions on Aerospace and Electronic Systems, volume 42, pp.3, 891 to 903 in 2006, a Multigenic Adaptive Pulse Compression (MAPC) algorithm based on iterative minimum mean square error (RMMSE) was proposed. The MAPC algorithm based on RMMSE can simultaneously inhibit the influence caused by multi-target echoes and different-address interference in radar target detection through open-loop adaptive filtering processing. However, the algorithm is designed for a radar pulse signal model and is not suitable for an MC-CDMA signal model which has multi-carrier characteristics and contains symbol modulation, so that the application of the algorithm in an MC-CDMA receiver in the field of spread spectrum communication is limited.

Disclosure of Invention

In order to solve the above problems, the present invention provides a method and a system for joint suppression of multipath and different-site interference of an MC-CDMA receiver, which can achieve suppression of the cross-correlation side lobe of multipath and different-site interference.

Without loss of generality, assume that the receiver simultaneously receives MC-CDMA signals transmitted from K transmitters, and the number of subcarriers modulated by the MC-CDMA signals is N_cThe receiver needs K receiving channels, where the receiving channel K is used to demodulate a signal of the transmitter K from the received combined signal y, and K is 0, 1.

A multi-path and different-address interference combined suppression method for a multi-carrier code division multiple access receiver comprises the following steps:

s1: estimating an initial value of the complex amplitude of the nth subcarrier of the kth receiving channel

A value of 1 is set, where K is 0,1, K-1, N is 1,2, N_cL is a sampling point index in one spreading code period, and L is the number of sampling points in one spreading code period;

the complex amplitude is defined as

Wherein A is_k,pThe amplitude of the signal arriving at the receiver via path p for transmitter k; p is the number of different arrival paths from the transmitter to the receiver; b_k,n(i) For the i-th bit of information modulated on the subcarrier n of the transmitter k, T_sFor bit information bit width, f_nIs the carrier frequency corresponding to the subcarrier n.

S2: estimating an initial value from the complex amplitude

Respectively calculating three delay correlation functions rho corresponding to each subcarrier of each receiving channel_k,n(l,L)、ρ_k,n(l,0) and ρ_k,n(L, -L), wherein

d is L,0, -L, is a conjugate symbol;

s3: based on the iterative minimum mean square error criterion, the three delay correlation functions are adopted to respectively calculate the filter coefficients corresponding to the subcarriers of the receiving channels

Specifically, the method comprises the following steps:

wherein the content of the first and second substances,

represents a sequence of received signal samples within one spreading code period of the receiver;

represents a sequence of spreading code samples corresponding to a subcarrier n of a transmitter k within one spreading code period, whereinf_sAs a sampling rate, c_k(l) Transmitting a spreading code uniformly modulated by a signal for a transmitter k;

is composed of

The shift amount is | j |; sigma²Is the noise power, I_LIs an L × L identity matrix, the superscript H denotes a conjugate transpose, the superscript T denotes a transpose, E [ 2 ]]Indicating a desire;

s4: according to the filter coefficient

Sampling sequence for received signal

Filtering to obtain complex amplitude estimation value corresponding to each subcarrier of each receiving channel

Specifically, the method comprises the following steps:

s5: the complex amplitude estimation value

The initial value of the complex amplitude estimation of step S2 is replaced

Then, repeating the steps S2-S4 to obtain a new complex amplitude estimated value

And analogizing until the repetition times reach a set value to obtain a final complex amplitude estimation value

S6: respectively calculating the final complex amplitude estimated value of different sub-carriers of each receiving channel

Module mean value of

Averaging the modes

As the complex amplitude of each receiving channel after multi-path and different-address interference combined suppression.

A multi-path and different-address interference combined suppression system for multi-carrier CDMA receiver features that the MC-CDMA signals from K transmitters are received by receiver at same time, and the number of sub-carriers modulated by MC-CDMA signal is N_cThe receiver corresponds to K receiving channels and comprises a complex amplitude initial value setting module, a correlation function calculating module, a filter coefficient calculating module, a filtering module and an average value calculating module;

the complex amplitude initial value setting module is used for setting the nth complex amplitude initial value of the kth receiving channel

A value of 1 is set, where K is 0,1, K-1, N is 1,2, N_cL is the index of sampling points in a spreading code period, and L is the number of sampling points in a spreading code period;

the correlation function calculation module is used for estimating an initial value according to the complex amplitude

Respectively calculating three delay correlation functions rho corresponding to each subcarrier of each receiving channel_k,n(l,L)、ρ_k,n(l,0) and ρ_k,n(L, -L), wherein

d is L,0, -L, is a conjugate symbol;

the filter coefficient calculation module is used for calculating a filter coefficient based on an iterative minimum mean square error criterionThen, the three delay correlation functions are adopted to respectively calculate the filter coefficients corresponding to the sub-carriers of each receiving channel

Specifically, the method comprises the following steps:

wherein the content of the first and second substances,

represents a sequence of received signal samples within one spreading code period of the receiver;

representing a sequence of spreading code samples corresponding to a subcarrier n of transmitter k within one spreading code period,

is composed of

The shift amount is | j |; sigma²Is the noise power, I_LIs an L × L identity matrix, the superscript H denotes a conjugate transpose, the superscript T denotes a transpose, E [ 2 ]]Indicating a desire;

the filtering module is used for obtaining the filter coefficient according to the filter coefficient

Sampling sequence for received signal

Filtering to obtain complex amplitude estimation value corresponding to each subcarrier of each receiving channel

Specifically, the method comprises the following steps:

the correlation function calculation module is further configured to calculate a correlation function based on the complex amplitude estimation value

Recalculating three delay correlation functions corresponding to each subcarrier of the transmitter; the filter coefficient calculation module is also used for recalculating the filter coefficients according to the three delay correlation functions obtained by recalculation; the filtering module is further used for recalculating the complex amplitude estimation value according to the recalculated filter coefficient; by analogy, the three modules form closed loop iteration until the iteration times reach a set value to obtain a final complex amplitude estimation value

The mean value calculating module is used for calculating the final complex amplitude estimated value of different subcarriers of each receiving channel

Module mean value of

Averaging the modesAs the complex amplitude of each receiving channel after multi-path and different-address interference combined suppression.

Has the advantages that:

the invention provides a multi-path and different-address interference combined suppression method and a system of a MC-CDMA receiver, which can realize the suppression of the cross-correlation caused by the multi-path and different-address interference by carrying out the open-loop adaptive filtering based on the iterative minimum mean square error criterion on the combined signals of the MC-CDMA signals transmitted by a plurality of transmitters and reaching the receiver through a plurality of paths, obtain the complex amplitude estimation of signals at different delays in the observation time and realize the suppression of the cross-correlation side lobe of the multi-path and different-address interference;

specifically, three delay correlation functions are obtained based on different delay complex amplitude correlation characteristics, and then filter coefficients are corrected; and respectively estimating the complex amplitude corresponding to each subcarrier according to the multi-carrier characteristic of the MC-CDMA signal model, and further adopting a modular mean value as final output according to the symbol modulation characteristic of the MC-CDMA signal, so that the information of all subcarriers is utilized, the finally output subcarrier complex amplitude has higher signal-to-noise ratio, and the requirements of resisting multipath and different-address interference of the MC-CDMA receiver in the conventional spread spectrum communication field are met.

Drawings

Fig. 1 is a flowchart of a multi-path, different-address interference joint suppression method for a multi-carrier cdma receiver according to the present invention;

fig. 2 is a schematic block diagram of a multi-path and inter-site interference joint suppression system of a multi-carrier cdma receiver according to the present invention.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.