CN104767547A - Spread spectrum communication multi-site interference elimination method - Google Patents

Abstract

The invention discloses a spread spectrum communication multi-site interference elimination method, and relates to spread spectrum communication systems. When multiple spread spectrum signals exist, a signal receiving end conducts spread spectrum signal receiving demodulation, and the multi-site interference elimination and signal demodulation method is adopted. The method comprises the steps of 1, calculating a coherent integral value of each signal and estimating the amplitude of each signal; 2, calculating a cross-correlation matrix through local pseudo codes, and calculating a compound matrix; 3, sorting the signals and the compound matrix, and obtaining a generalized inverse matrix of the sorted matrix; 4, conducting traversal on some sorted signals and conducting influence elimination; 5, conducting interference elimination and detection on remaining signals; 6, selecting out a demodulation result corresponding to the minimum detection residual value. According to the spread spectrum communication multi-site interference elimination method, multi-site interference caused by multiple spread spectrum signal concurrent transmission can be effectively eliminated with the low operational complexity, the demodulation error rate of the multiple spread spectrum signals is greatly lowered, and the spread spectrum communication multi-site interference elimination method has the advantages of being novel, creative, flexible and practical.

Description

A kind of spread spectrum communication multiple access interference cancellation method

Technical field

The present invention relates to spread spectrum communication field, especially relate to a kind of spread spectrum communication multiple access interference cancellation method.

Background technology

At present, in satellite navigation, space flight measurement and control, civilian mobile communication system, spread spectrum communication system is widely applied, a new generation's spread spectrum communication system requires to utilize limited bandwidth resource to transmit the data of the low spreading gain of multipath high-speed rate, the multi-access inference impact that it brings is very serious, needs more efficiently multiple access interference cancellation method.Multi-access interference suppression technology common at present can be divided into joint-detection and interference elimination two class, traditional associated detecting method comprises maximum likelihood method (ML), Zero-forcing method (ZF) and minimum mean square error method (MMSE), and common interference elimination method comprises serial interference elimination (SIC), parallel interference canceller (PIC) and part parallel interference elimination method (PPIC).

Prior art is difficult to realize unification in method complexity and interference elimination performance, as maximum likelihood method best performance but complexity is high does not have realizability, lower but the performance of Zero-forcing method computational complexity is difficult to meet actual needs, and then makes the engineer applied of its spread spectrum communication multi-access interference suppression technology and the further raising of systematic function receive very big restriction.

Summary of the invention

The object of the invention is to avoid the deficiency of above-mentioned background technology and provide a kind of and there is high interference eliminate performance and have the spread spectrum communication multiple access interference cancellation method of lower complexity simultaneously concurrently.This method is applicable to when there is multipath spread-spectrum signal, and signal receiving end carries out spread-spectrum signal receiving demodulation, the multiple access interference cancellation adopted and signal demodulating method; This method has engineering realizability, has method structure flexibly simultaneously, can require to regulate method, to meet the demand of engineer applied according to software and hardware condition and interference elimination performance.

The object of the present invention is achieved like this, and a kind of spread spectrum communication multiple access interference cancellation method, comprises the following steps:

1. receiving terminal adopts the method for matched filtering to obtain the coherent integration vector of N road spread-spectrum signal to the N road spread-spectrum signal received respectively, adopts the method for signal amplitude estimation to estimate the amplitude of N road spread-spectrum signal in real time respectively to coherent integration vector;

2. the pseudo-code that local generation is corresponding with N road spread-spectrum signal, calculate cross-correlation matrix by each road pseudo-code, the amplitude of N road spread-spectrum signal being multiplied with cross-correlation matrix obtains compound matrice;

3. compound matrice are carried out row sequence and obtain according to the modulus value of its column vector is square ascending the compound matrice that sort, according to the order of elements of order change adjustment coherent integration vector between compound matrice column vector and the signal sequence of N road spread-spectrum signal, obtain the generalized inverse matrix of sequence compound matrice;

4. the candidate signal set obtaining front d road signal is traveled through to the 1st road to d road signal of the N road spread-spectrum signal after sequence according to digital baseband signal modulation system, candidate signal set is arranged with d before sequence compound matrice the multi-access inference vector obtaining front d road signal that is multiplied gather, the coherent integration vector set that the set of multi-access inference vector obtains removing front d road signal disturbing is deducted in coherent integration vector after sequence, d is integer and d ∈ [1, N];

5. adopt the method for serial interference elimination to detect respectively to d+1 road to the N road signal of the coherent integration vector set of removing front d road signal disturbing, obtain the set of candidate signal vector and the set of detection residual error of the N-d road signal removing front d road signal disturbing;

6. from the set of detection residual error, minimum detection residual error is selected, the candidate signal vector that minimum detection residual error is corresponding is selected from the set of candidate signal vector, according to step 3. in the order of elements of this candidate signal vector of clooating sequence reverse adjustment of element of coherent integration vector, the signal vector that the N road spread-spectrum signal order obtained and receive is identical, this signal vector is exactly the spread-spectrum signal demodulation result finally removing multi-access inference impact;

Complete spread spectrum communication multiple access interference cancellation method.

Wherein, the 1st described road to d road signal for sort compound matrice the row being less than predetermined threshold value corresponding to sequence after N road spread-spectrum signal before d road spread-spectrum signal, d be integer and d ∈ [1, N], N be greater than 1 integer.

Wherein, described step 3. in sequence compound matrice generalized inverse matrix be:

H _ordered ⁺＝(H _ordered ^HH _ordered) ^-1H _ordered

In formula, H _orderedrepresent sequence compound matrice, H _ordered ⁺represent the generalized inverse matrix of sequence compound matrice.

Wherein, before described removal, the coherent integration vector set of d road signal disturbing is combined into:

Y-H _ordered(：，1：d)×(b ₁(k ₁)，b ₂(k ₂)，…b _d(k _d)) ^T

In formula, Y represents the vector of the coherent integration after sequence, H _orderedrepresent sequence compound matrice, b _d(k _d) be the kth of d road spread-spectrum signal _dthe information bit of individual candidate signal, (k ₁, k ₂..., k _d) get (1,1 ..., 1) and to (N _s, N _s..., N _s) integer, N _sfor modulation constellation number, before removing, the coherent integration vector set of d road signal disturbing is by N _s ^dindividual vector composition.

Wherein, described detection set of residuals is combined into: r ²=R _n-d+1 ²,

R _N-j＝H _ordered ⁺(：，d+1：M-j)×(Y-H _ordered(：，1：d)×

(b ₁(k ₁)，b ₂(k ₂)，…b _d(k _d)) ^T-H _ordered(：，N-j+1：N)×

(x _N-j+1，…，x _N) ^T)，

x _N-i(k ₁，k ₂，…k _d)＝Q(R _N-j)，

In formula, r ²represent and detect residual error set, N is the way of spread-spectrum signal, and d ∈ [1, N], j are integer and j ∈ [0, d-1], Q () expression rounds judgement, H _orderedrepresent sequence compound matrice, H _ordered ⁺represent the generalized inverse matrix of sequence compound matrice, M represents the data length of transmission, (k ₁, k ₂... k _d) get (1,1 ..., 1) and to (N _s, N _s... N _s) integer, b _d(k _d) represent the kth of d road spread-spectrum signal _dthe information bit of individual candidate signal, N _sfor modulation constellation number.

The present invention compares background technology tool and has the following advantages:

I spread spectrum communication multiple access interference cancellation method that () the present invention proposes, based on deep theory analysis, there is comparatively unique method structure, can with lower computational complexity, the multiple access interference cancellation that realization approaches maximum likelihood property and detection perform, have novelty and creationary feature.

(ii) the spread spectrum communication multiple access interference cancellation method of the present invention's proposition, there is method structure flexibly, its computational complexity and multiple access interference cancellation performance can adjust with method structural change, different software and hardware conditions and multi-access inference environment can be adapted to, there is stronger engineering realizability, there is the feature of practicality.

Accompanying drawing explanation

Fig. 1 is spread spectrum communication multiple access interference cancellation method flow diagram of the present invention;

Fig. 2 is system construction drawing of the present invention;

Fig. 3 is the multiple access interference cancellation method flow diagram based on BPSK spread-spectrum signal of the present invention.

Embodiment

Below in conjunction with drawings and Examples, the present invention will be further described.

System configuration of the present invention as shown in Figure 2, signal pickup assembly is analog/digital (A/D) conversion equipment, for the multipath spread-spectrum received signal is converted to digital signal simultaneously, signal receiving processing unit is the data processing equipment with stronger operational capability, and the spread-spectrum signal that this device is used for gathering carries out multiple access interference cancellation and demodulation.

As shown in Figure 1, the method specifically comprises the following steps spread spectrum communication multiple access interference cancellation method flow diagram of the present invention:

Step 101: receiving terminal adopts the method for matched filtering to obtain the coherent integration vector of N road spread-spectrum signal to the N road spread-spectrum signal received respectively, adopts the method for signal amplitude estimation to estimate the amplitude of N road spread-spectrum signal in real time respectively to coherent integration vector;

Step 102: the pseudo-code that local generation is corresponding with N road spread-spectrum signal, calculate cross-correlation matrix by each road pseudo-code, the amplitude of N road spread-spectrum signal being multiplied with cross-correlation matrix obtains compound matrice;

Step 103: compound matrice are carried out row sequence and obtain according to the modulus value of its column vector is square ascending the compound matrice that sort, according to the order of elements of order change adjustment coherent integration vector between compound matrice column vector and the signal sequence of N road spread-spectrum signal, obtain the generalized inverse matrix of sequence compound matrice;

Step 104: the candidate signal set obtaining front d road signal is traveled through according to digital baseband signal modulation system to the 1st road to d road signal of the N road spread-spectrum signal after sequence, candidate signal set is arranged with d before sequence compound matrice the multi-access inference vector obtaining front d road signal that is multiplied gather, in the coherent integration vector after sequence, deduct the coherent integration vector set that the set of multi-access inference vector obtains removing front d road signal disturbing;

Step 105: adopt the method for serial interference elimination to detect respectively to d+1 road to the N road signal of the coherent integration vector set of removing front d road signal disturbing, obtains the set of candidate signal vector and the set of detection residual error of the N-d road signal removing front d road signal disturbing;

Step 106: select minimum detection residual error from the set of detection residual error, the candidate signal vector that minimum detection residual error is corresponding is selected from the set of candidate signal vector, according to step 3. in the order of elements of this candidate signal vector of clooating sequence reverse adjustment of element of coherent integration vector, the signal vector that the N road spread-spectrum signal order obtained and receive is identical, this signal vector is exactly the spread-spectrum signal demodulation result finally removing multi-access inference impact.

Fig. 3 is the multiple access interference cancellation method flow diagram of embodiment, the radiofrequency signal adopting BPSK to modulate in embodiment and the carrier frequency f of modulation signal _swith information frequency f _dpass be f _s=Nf _d, multiple access interference cancellation method concrete steps comprise:

Step 201: to count N according to BPSK digital baseband modulating mode determination modulation constellation _s=2;

Step 202: receiving terminal adopts the method for matched filtering to obtain the coherent integration vector of each road signal to the multipath spread-spectrum signal received respectively, adopts signal amplitude method of estimation to estimate the amplitude of each road signal in real time respectively to the coherent integration vector of each road signal;

Embodiment: the spread-spectrum signal setting receiving terminal to receive as:

$r\left(t\right)={\mathrm{\Σ}}_{i=1}^N{A}_i{b}_{i}P{N}_i\left(t\right)+n\left(t\right),t\∈[0,T_b],i\∈[1,N]$

In formula, r (t) represents N road spread-spectrum signal, A _ithe amplitude of the i-th road spread-spectrum signal, b _ithe information bit of the i-th road spread-spectrum signal, PN _it () is the spreading code of the i-th road spread-spectrum signal, T _bbe the time width of the information bit that spread-spectrum signal comprises, N is the way of spread-spectrum signal, and n (t) is average is zero, and variance is σ ²additive white Gaussian noise.

The coherent integration that spread-spectrum signal obtains after the matched filtering of k road is:

$n_k={\∫}_0^{T}n\left(t\right)P{N}_k\left(t\right)\mathrm{dt}$

${\mathrm{\ρ}}_{\mathrm{ik}}={\∫}_0^{T}P{N}_i\left(t\right)P{N}_k\left(t\right)\mathrm{dt}$

In formula, y _kfor coherent integration; T is the time of coherent integration; y _ksection 1 be the useful part of kth road spread-spectrum signal; y _ksection 2 be cross-correlation between other road spread-spectrum signal and kth road spread-spectrum signal, i.e. multi-access inference; y _ksection 3 be the interference that interchannel noise causes; ρ _ikit is the cross-correlation of the i-th signal spread-spectrum Ma Yuk road, road signal spread-spectrum code; A _ithe amplitude of the i-th road spread-spectrum signal, b _iit is the information bit of the i-th road spread-spectrum signal.

The coherent integration vector that then N road spread-spectrum signal obtains through matched filtering is:

$\stackrel{\→}{Y}={[y_1,y_2,...Y_N]}^T,$ In formula, represent coherent integration vector.

Step 203: the pseudo-code that local generation is corresponding with N road spread-spectrum signal, calculate cross-correlation matrix by each road pseudo-code, the amplitude of N road spread-spectrum signal being multiplied with cross-correlation matrix obtains compound matrice;

Embodiment: the cross-correlation matrix that each road pseudo-code produced by this locality calculates is:

$R=\left[\begin{array}{cccc}{\mathrm{\ρ}}_{11}& {\mathrm{\ρ}}_{12}& ...& {\mathrm{\ρ}}_{1N}\\ {\mathrm{\ρ}}_{21}& {\mathrm{\ρ}}_{22}& ...& {\mathrm{\ρ}}_{2N}\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ {\mathrm{\ρ}}_{N1}& {\mathrm{\ρ}}_{N2}& ...& {\mathrm{\ρ}}_{\mathrm{NN}}\end{array}\right]$

The amplitude of N road spread-spectrum signal is:

Compound matrice are:

In formula, represent cross-correlation matrix, represent amplitude, represent compound matrice.

Step 204: compound matrice are carried out row sequence and obtain according to the modulus value of its column vector is square ascending the compound matrice that sort, according to the order of elements of order change adjustment coherent integration vector between compound matrice column vector and the signal sequence of N road spread-spectrum signal, obtain the generalized inverse matrix of sequence compound matrice;

Embodiment: the modulus value square of compound matrice H column vector is:

In formula, h _ikrepresent the element of compound matrice H i-th row kth row, k ∈ [1, N].

The generalized inverse matrix of sequence compound matrice is:

H _ordered ⁺＝(H _ordered ^HH _ordered) ^-1H _ordered

In formula, H _orderedrepresent sequence compound matrice, H _ordered ⁺represent the generalized inverse matrix of sequence compound matrice, () ^hthe complex conjugate of matrix is got in representative, () ^-1represent inverse of a matrix matrix.

Compound matrice column vector modulus value inverse square detects mean square error in respective signal, and compound matrice are carried out row sequence be equivalent to carry out sorting according to detection mean square error according to the modulus value of its column vector is square ascending.

Step 205: the candidate signal set obtaining front d road signal is traveled through according to digital baseband signal modulation system to the 1st road to d road signal of the N road spread-spectrum signal after sequence, candidate signal set is arranged with d before sequence compound matrice the multi-access inference vector obtaining front d road signal that is multiplied gather, in the coherent integration vector after sequence, deduct the coherent integration vector set that the set of multi-access inference vector obtains removing front d road signal disturbing;

Embodiment: coherent integration vector set is combined into:

Y-H _ordered(：，1：d)×(b ₁(k ₁)，b ₂(k ₂)，…b _d(k _d)) ^T

In formula, Y represents the vector of the coherent integration after sequence, H _orderedrepresent sequence compound matrice, (k ₁, k ₂... k _d) get (1,1 ..., 1) to (2,2 ... 2) integer, b _dthe information bit of d road spread-spectrum signal, () ^trepresent transpose of a matrix matrix.

The set of coherent integration vector comprises 2 ^dindividual vector.

Step 206: what obtain step 205 comprises 2 ^dthe coherent integration vector set of d road signal disturbing before the removal of individual vector, from the signal of N road, adopt the method for serial interference elimination to detect respectively, until d+1 road, obtain the set of candidate vectors of the N-d road signal removing front d road signal disturbing and detect residual error set;

Embodiment: r ²=R _n-d+1 ²;

R _N-j＝H _ordered ⁺(：，d+1：M-j)×(Y-H _ordered(：，1：d)×

(b ₁(k ₁)，b ₂(k ₂)，…b _d(k _d)) ^T-H _ordered(：，N-j+1：N)×

(x _N-j+1，…，x _N) ^T)；

x _N-i(k ₁，k ₂，…k _d)＝Q(R _N-j)

In formula, r ²represent and detect residual error set, N is the way of spread-spectrum signal, d ∈ [1, N], j ∈ [0, d-1], and Q () expression rounds judgement, H _orderedrepresent sequence compound matrice, H _ordered ⁺represent the generalized inverse matrix of sequence compound matrice, M represents the data length of transmission, (k ₁, k ₂..., k _d) get (1,1 ..., 1) to (2,2 ..., 2) integer, () ^trepresent transpose of a matrix matrix.

Step 207: from comprising 2 ^dminimum detection residual error is selected, from comprising 2 in the detection residual error set of individual metrical error ^dcandidate signal vector corresponding to minimum detection residual error is selected in the candidate signal vector set of individual candidate signal vector, according to step 3. in the order of elements of this candidate signal vector of clooating sequence reverse adjustment of element of coherent integration vector, obtain the signal vector identical with receiving spread frequency signal order, this signal vector is exactly the spread-spectrum signal demodulation result finally removing multi-access inference impact.

In addition to the implementation, the present invention can also have other execution modes.All employings are equal to the technical scheme of replacement or equivalent transformation form, all drop on the protection range of application claims.

Claims (5)

1. a spread spectrum communication multiple access interference cancellation method, is characterized in that: comprise the following steps:

1. receiving terminal adopts the method for matched filtering to obtain the coherent integration vector of N road spread-spectrum signal to the N road spread-spectrum signal received respectively, adopts the method for signal amplitude estimation to estimate the amplitude of N road spread-spectrum signal in real time respectively to coherent integration vector;

2. the pseudo-code that local generation is corresponding with N road spread-spectrum signal, calculate cross-correlation matrix by each road pseudo-code, the amplitude of N road spread-spectrum signal being multiplied with cross-correlation matrix obtains compound matrice;

3. compound matrice are carried out row sequence and obtain according to the modulus value of its column vector is square ascending the compound matrice that sort, according to the order of elements of order change adjustment coherent integration vector between compound matrice column vector and the signal sequence of N road spread-spectrum signal, obtain the generalized inverse matrix of sequence compound matrice;

4. the candidate signal set obtaining front d road signal is traveled through to the 1st road to d road signal of the N road spread-spectrum signal after sequence according to digital baseband signal modulation system, candidate signal set is arranged with d before sequence compound matrice the multi-access inference vector obtaining front d road signal that is multiplied gather, the coherent integration vector set that the set of multi-access inference vector obtains removing front d road signal disturbing is deducted in coherent integration vector after sequence, d is integer and d ∈ [1, N];

5. adopt the method for serial interference elimination to detect respectively to d+1 road to the N road signal of the coherent integration vector set of removing front d road signal disturbing, obtain the set of candidate signal vector and the set of detection residual error of the N-d road signal removing front d road signal disturbing;

6. from the set of detection residual error, minimum detection residual error is selected, the candidate signal vector that minimum detection residual error is corresponding is selected from the set of candidate signal vector, according to step 3. in the order of elements of this candidate signal vector of clooating sequence reverse adjustment of element of coherent integration vector, the signal vector that the N road spread-spectrum signal order obtained and receive is identical, this signal vector is exactly the spread-spectrum signal demodulation result finally removing multi-access inference impact;

Complete spread spectrum communication multiple access interference cancellation method.

2. a kind of spread spectrum communication multiple access interference cancellation method according to claim 1, it is characterized in that: d road spread-spectrum signal before the N road spread-spectrum signal after the sequence of the 1st described road to d road signal corresponding to the row being less than predetermined threshold value of the compound matrice that sort, d is integer and d ∈ [1, N], N be greater than 1 integer.

3. a kind of spread spectrum communication multiple access interference cancellation method according to claim 1, is characterized in that: the described step 3. middle generalized inverse matrix sorting compound matrice is:

H _ordered ⁺＝(H _ordered ^HH _ordered) ^-1H _ordered

In formula, H _orderedrepresent sequence compound matrice, H _ordered ⁺represent the generalized inverse matrix of sequence compound matrice.

4. a kind of spread spectrum communication multiple access interference cancellation method according to claim 1, is characterized in that: before described removal, the coherent integration vector set of d road signal disturbing is combined into:

Y-H _ordered(：，1：d)×(b ₁(k ₁)，b ₂(k ₂)，…b _d(k _d)) ^T

In formula, Y represents the vector of the coherent integration after sequence, H _orderedrepresent sequence compound matrice, b _d(k _d) be the kth of d road spread-spectrum signal _dthe information bit of individual candidate signal, (k ₁, k ₂..., k _d) get (1,1 ..., 1) and to (N _s, N _s..., N _s) integer, N _sfor modulation constellation number, before removing, the coherent integration vector set of d road signal disturbing is by N _s ^dindividual vector composition.

5. a kind of spread spectrum communication multiple access interference cancellation method according to claim 1, is characterized in that: described detection set of residuals is combined into: r ²=R _n-d+1 ²,

R _N-j＝H _ordered ⁺(：，d+1：M-j)×(Y-H _ordered(：，1：d)×

(b ₁(k ₁)，b ₂(k ₂)，…b _d(k _d)) ^T-H _ordered(：，N-j+1：N)×

(x _N-j+1，…，x _N) ^T)，

x _N-j(k ₁，k ₂，…k _d)＝Q(R _N-j)，

In formula, r ²represent and detect residual error set, N is the way of spread-spectrum signal, and d ∈ [1, N], j are integer and j ∈ [0, d-1], Q () expression rounds judgement, H _orderedrepresent sequence compound matrice, H _ordered ⁺represent the generalized inverse matrix of sequence compound matrice, M represents the data length of transmission, (k ₁, k ₂... k _d) get (1,1 ..., 1) and to (N _s, N _s... N _s) integer, b _d(k _d) represent the kth of d road spread-spectrum signal _dthe information bit of individual candidate signal, N _sfor modulation constellation number.