CN107342786B - Signal blind despread method based on ILSP algorithm - Google Patents
Signal blind despread method based on ILSP algorithm Download PDFInfo
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- CN107342786B CN107342786B CN201710531404.7A CN201710531404A CN107342786B CN 107342786 B CN107342786 B CN 107342786B CN 201710531404 A CN201710531404 A CN 201710531404A CN 107342786 B CN107342786 B CN 107342786B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
- H04B1/7103—Interference-related aspects the interference being multiple access interference
- H04B1/7105—Joint detection techniques, e.g. linear detectors
- H04B1/71057—Joint detection techniques, e.g. linear detectors using maximum-likelihood sequence estimation [MLSE]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0238—Channel estimation using blind estimation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/024—Channel estimation channel estimation algorithms
- H04L25/0242—Channel estimation channel estimation algorithms using matrix methods
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Abstract
The invention belongs to blind despread technical field more particularly to a kind of short code DS-CDMA signal blind despread methods of multipath transmisstion based on ILSP algorithm.The present invention is the synchronization short code DS-CDMA signal blind despread method propagated based on ILSP algorithm through multipath channel, by the synchronization short code DS-CDMA signal modeling received at matrix form, then according to the special construction of information code matrix and ± 1 characteristic, receipt signal matrix are decomposed using ILSP algorithm, obtain the estimated matrix of the combined channel matrix of the Sequence composition obtained by user's frequency expansion sequence and channel parameter convolutionIt finally de-spreads to obtain user information code matrix using combined channel matrix.Even if Computer Simulation shows that the present invention still has preferable performance under Low SNR.
Description
Technical field
The invention belongs to blind despread technical field more particularly to a kind of short code DS- of the multipath transmisstion based on ILSP algorithm
CDMA signal blind despread method.
Background technique
Direct Sequence Spread Spectrum (DSSS, the Direct Sequence Spread Spectrum) communication technology is outstanding due to its
Anti-interference and ability of anti-interception, be widely used in the civilian and military communications field, therefore there is very far-reaching practical valence
Value and research significance.The DSSS communication technology is multiplied using the frequency expansion sequence of high-speed with information code sequence when signal is sent,
So that the frequency spectrum of signal is widened, spectrum density is reduced, in recipient, then with high speed sequence identical when sending with receive
Signal multiplication makes the spectrum recovery of signal complete despreading, and noise and the frequency spectrum of interference are extended, and spectrum density reduces, this
Sample is just easy to filter out noise and interference from signal.For cooperate recipient, can with the frequency expansion sequence being known in advance from
The information code sequence for de-spreading and being transmitted in signal is received, but non-cooperation recipient is needed at received signal
Reason, therefrom extracts signal spread-spectrum sequence, is then de-spread to obtain transmission information code sequence with the frequency expansion sequence that estimation obtains.It is multi-purpose
Family scene, each user use different spread spectrum code sequences, and obtained frequency expansion sequence at this time is DS-CDMA signal, in reality
DS-CDMA signal is more widely applied in, therefore to the blind despread research significance of DS-CDMA signal bigger.
Summary of the invention
It is an object of the invention to overcome the deficiencies in the prior art, propose a kind of signal blind despread based on ILSP algorithm
Method, method proposed by the present invention are suitable for the synchronization short code DS-CDMA signal blind despread problem propagated into multipath channel.
For realize foregoing invention purpose, the present invention the following steps are included:
S1, the short code DS-CDMA signal through multipath transmisstion received are represented byWherein, R indicates the number of user, arFor the signal amplitude of r-th of user,
brFor the information code sequence of r-th of user, M is information code number, hrJoin for the spread spectrum code sequence and multipath channel of r-th of user
Several convolution sequences, n (n) are that variance is σ2White Gaussian noise；
S2, short code DS-CDMA signal through multipath transmisstion matrix form be written as Y=HAST+ N, wherein JR × JR dimension pair
Angular moment battle array A=diag (a1,…a1,……aR,…aR) it is signal amplitude matrix, J is the letter of the intersymbol interference due to caused by multipath
Code number is ceased, L × JR dimension matrix H is made of the frequency expansion sequence of R user and the sequences h after multi-path coefficients convolution and zero construction
Matrix, M × JR dimension matrix S are to be constructed of Toeplitz matrix by the element of (M+J) × R dimension information code matrix B, and matrix N is
Receive the matrix form of noise in signal；
S3, for DS-CDMA signal matrix model Y, due to the Toeplitz matrix special construction and ± 1 characteristic of matrix S,
Fuzzy matrix can destroy the Toeplitz structure of matrix S if it exists, and matrix A is diagonal matrix, i.e., only can respectively arrange matrix H production
Raw scale influences, and only need to be normalized and can eliminate to H each column, therefore decompose to obtain S to matrix Y using ILSP algorithm
The estimated matrix of matrix and H-matrixWithIt is specific as follows:
S31, i=0, random initializtion (M+J) × R is enabled to tie up matrixAnd by matrixObtain Toeplitz form square
Battle array
S32, i=i+1 is enabled, calculated 1≤r≤R, eliminating scale influences；
S33, calculatingBy matrixObtain information code matrixAgain by matrixIt obtains
Toeplitz formal matrices
S34, it repeats S32-S33 and until algorithmic statement or reaches maximum number of iterations, wherein the condition of algorithmic statement isε is convergent threshold value, ε=1 × 10-9, the maximum number of iterations is 50 times；
S4, with the estimated matrix of finally obtained H-matrixIt is de-spread to obtain the estimated matrix of information matrix s-matrix
Further, repeat S31-S34, i.e., repeatedly ILSP algorithm Q time, select iteration effect it is best once as finally
As a result, wherein Q is the natural number being not zero.
Further, S31-S34, i.e. repeatedly ILSP algorithm algorithm 40 times, the primary work for selecting iteration effect best are repeated
For final result.
The beneficial effects of the present invention are:
The present invention is the synchronization short code DS-CDMA signal blind despread method propagated based on ILSP algorithm through multipath channel, will
The synchronization short code DS-CDMA signal modeling received is then special according to the special construction of information code matrix and ± 1 at matrix form
Property, decomposes receipt signal matrix using ILSP algorithm, obtains being obtained by user's frequency expansion sequence and channel parameter convolution
The estimated matrix of the combined channel matrix of Sequence compositionIt finally de-spreads to obtain user information code square using combined channel matrix
Battle array.Even if Computer Simulation shows that the present invention still has preferable performance under Low SNR.
Detailed description of the invention
Fig. 1 is that one kind of the short code DS-CDMA signal blind despread method the present invention is based on ILSP algorithm multipath transmisstion is specific
Embodiment flow chart.
Fig. 2 is in the embodiment of the present invention 1, and the bit error rate of the information code Matrix Estimation matrix of different user number is with signal-to-noise ratio
Change curve.
Fig. 3 is the normalization mean square error of the combined channel Matrix Estimation matrix of different user number in the embodiment of the present invention 2
Difference with signal-to-noise ratio change curve.
Specific embodiment
The present invention will be described with reference to the accompanying drawing.
Embodiment 1,
This purpose implemented is to emulate to the information code matrix bit error rate of different user number with signal-to-noise ratio variation,
Fig. 1 is a kind of specific embodiment party of the synchronization short code DS-CDMA signal propagated through multipath channel the present invention is based on ILSP algorithm
Formula flow chart.As shown in Figure 1, the present invention realizes that the synchronization short code DS-CDMA signal blind despread method of multipath transmisstion includes following
Step:
Step 1: the short code DS-CDMA signal through multipath transmisstion received is represented by
Wherein, R indicates the number of user, this is embodied as R=3 and R=4, arFor the signal amplitude of r-th of user, sheet
It is random number, b in secondary implementationrFor the information code sequence of r-th of user, in this implementation, information code sequence and spread spectrum code sequence be all
For ± 1 sequence, M is information code number, this implements M=100, spreading gain L=31, and the multi-path channel parameters of a user are all
[1,0.9,0.7,0.5,0.3,0.15], hrFor the spread spectrum code sequence of r-th user and the convolution sequence of multi-path channel parameters, n
It (n) be variance is σ2White Gaussian noise.
Step 2: by step 1 it is found that the matrix form of the short code DS-CDMA signal through multipath transmisstion can be written as
Y=HAST+N
Wherein JR × JR ties up diagonal matrix A=diag (a1,…a1,……aR,…aR) be signal amplitude matrix, J be due to
The information code number of intersymbol interference caused by multipath, L × JR tie up the frequency expansion sequence and multi-path coefficients convolution that matrix H is R user
Matrix made of sequences h and zero afterwards constructs, M × JR dimension matrix S are configured to by the element of (M+J) × R dimension information code matrix B
Toeplitz matrix, matrix N be receive signal in noise matrix form.
The information code matrix of single userStructure be shown below
Step 3: for the DS-CDMA signal matrix model Y of above-mentioned introduction, since the Toeplitz matrix of matrix S is special
Structure and ± 1 characteristic, fuzzy matrix can destroy the Toeplitz structure of matrix S if it exists, and matrix A is diagonal matrix, i.e., only
Matrix H can respectively be arranged and generate scale influence, only H each column need to be normalized and can be eliminated, therefore we can be direct
Matrix Y is decomposed using ILSP algorithm to obtain the estimated matrix of s-matrix and H-matrixWith
Implement step:
I=0, random initializtion (M+J) × R is enabled to tie up matrixAnd by matrixObtain Toeplitz formal matrices
I=i+1 is enabled, is calculated 1≤r≤R, eliminating scale influences；
It calculatesBy matrixObtain information code matrixAgain by matrixObtain Toeplitz shape
Formula matrix
It repeats step (2)~(3) and until algorithmic statement or reaches maximum number of iterations, the condition of algorithmic statement is
Wherein, ε is convergent threshold value, is usually taken to be 1 × 10-9, in the method, maximum number of iterations is set as 50.
In order to improve algorithm performance, repeats step (1)~(4) repeatedly (this method is selected as 40), select iteration effect best
It is primary be used as final result.
Step 4: with the estimated matrix of finally obtained H-matrixIt is de-spread to obtain the estimation square of information matrix s-matrix
Battle array
Obtained estimated matrix is compared with former data matrix, counts the bit error rate, at the same with the conjunction under same case
Make communication and compares that (when cooperative communication, combined channel matrix H is it is known that by formula S=sign (H-1Y user can) be acquired
Information code matrix), and draw the curve that the bit error rate changes with signal-to-noise ratio.This implements to carry out 1000 Monte Carlo Experiments, most
The information code matrix bit error rate obtained eventually is as shown in Figure 2 with SNR change curve.As can be seen from the figure blind solution proposed by the present invention
Expanding method is functional in low signal-to-noise ratio, and the bit error rate increases with the increase of number of users, is consistent with theory.
Embodiment 2,
This purpose implemented is under the conditions of different user number, to the normalized mean squared error rate of joint channel matrix
It is emulated with SNR (Signal Noise Rate, signal-to-noise ratio) variation.It is R=3 and R=4 that this, which implements user's number, and its
Its condition is identical as implementing 1, and the normalized mean squared error of combined channel is calculated by following formula:
1000 Monte Carlo experiments are carried out, finally obtained combined channel matrix normalization mean square error changes with SNR
Curve is as shown in Figure 3.As can be seen from the figure blind despread method proposed by the present invention is functional in low signal-to-noise ratio, connection
The normalized mean squared error for closing channel reduces with the increase of signal-to-noise ratio, i.e. gradually approaching to reality value, is consistent with theory.
Claims (3)
1. a kind of signal blind despread method of the software flow ILSP algorithm of Multiple Cycle being alternately performed based on ectonexine, special
Sign is, includes the following steps:
S1, the short code DS-CDMA signal through multipath transmisstion received are represented byWherein, R indicates the number of user, arFor the signal amplitude of r-th of user,
brFor the information code sequence of r-th of user, M is information code number, hrJoin for the spread spectrum code sequence and multipath channel of r-th of user
Several convolution sequences, L are spreading gain, and n (n) is that variance is σ2White Gaussian noise；
S2, short code DS-CDMA signal through multipath transmisstion matrix form be written as Y=HAST+ N, wherein JR × JR is tieed up to angular moment
Battle array A=diag (a1,…,a1,……aR,…aR) it is signal amplitude matrix, J is the information of the intersymbol interference due to caused by multipath
Code number, L × JR tie up matrix H as the frequency expansion sequence of R user and square made of the sequences h after multi-path coefficients convolution and zero construction
Battle array, M × JR dimension matrix S are to be constructed of Toeplitz matrix by the element of (M+J) × R dimension information code matrix B, and matrix N is to connect
The matrix form of noise in the collection of letters number；
S3, for DS-CDMA signal matrix model Y, due to the Toeplitz matrix special construction and ± 1 characteristic of matrix S, if depositing
The Toeplitz structure of matrix S can be destroyed in fuzzy matrix, and matrix A is diagonal matrix, i.e., only can respectively arrange matrix H and generate ruler
Degree influences, and only need to be normalized and can eliminate to H each column, therefore decompose to obtain s-matrix to matrix Y using ILSP algorithm
With the estimated matrix of H-matrixWithIt is specific as follows:
S31, i=0, random initializtion (M+J) × R is enabled to tie up matrixAnd by matrixObtain Toeplitz formal matrices
S32, i=i+1 is enabled, calculatedEliminating scale influences；
S33, calculatingBy matrixObtain information code matrixAgain by matrixObtain Toeplitz shape
Formula matrix
S34, it repeats S32-S33 and until algorithmic statement or reaches maximum number of iterations, wherein the condition of algorithmic statement isε is convergent threshold value, ε=1 × 10-9, the maximum number of iterations is 50 times；
S4, with the estimated matrix of finally obtained H-matrixIt is de-spread to obtain the estimated matrix of information matrix s-matrix
2. a kind of signal blind despread method based on ILSP algorithm according to claim 1, it is characterised in that: repeat S31-
S34 that is, repeatedly ILSP algorithm Q times, selects best primary as final result of iteration effect, wherein Q is the nature being not zero
Number.
3. a kind of signal blind despread method based on ILSP algorithm according to claim 1, it is characterised in that: repeat S31-
S34, i.e. repeatedly ILSP algorithm 40 times select best primary as final result of iteration effect.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6445692B1 (en) * | 1998-05-20 | 2002-09-03 | The Trustees Of The Stevens Institute Of Technology | Blind adaptive algorithms for optimal minimum variance CDMA receivers |
| CN105490705A (en) * | 2016-01-07 | 2016-04-13 | 电子科技大学 | ILSP algorithm-based synchronous DS-CDMA signal blind de-spreading method |
| CN105634544A (en) * | 2016-01-07 | 2016-06-01 | 电子科技大学 | Blind despreading method of synchronous long code DS-CDMA (Direct Sequence-Code Division Multiple Access) signals |
-
2017
- 2017-07-03 CN CN201710531404.7A patent/CN107342786B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6445692B1 (en) * | 1998-05-20 | 2002-09-03 | The Trustees Of The Stevens Institute Of Technology | Blind adaptive algorithms for optimal minimum variance CDMA receivers |
| CN105490705A (en) * | 2016-01-07 | 2016-04-13 | 电子科技大学 | ILSP algorithm-based synchronous DS-CDMA signal blind de-spreading method |
| CN105634544A (en) * | 2016-01-07 | 2016-06-01 | 电子科技大学 | Blind despreading method of synchronous long code DS-CDMA (Direct Sequence-Code Division Multiple Access) signals |
Non-Patent Citations (3)
| Title |
|---|
| A Semidefinite Relaxation Approach to Blind Despreading of Long-Code DS-SS Signal With Carrier Frequency Offset;Huaguo Zhang等;《IEEE Signal Processing Letters》;20130320;第20卷(第7期);705-708 * |
| Blind synchronization algorithm for the DS-CDMA signals;Huaguo Zhang等;《2009 International Conference on Communications, Circuits and Systems》;20090725;469-472 * |
| 一种改进的异步CDMA信号的盲解扩算法;张花国，李鑫;《电子技术应用》;20181031;第41卷(第10期);77-80 * |
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