CN107342786A - Signal blind despread method based on ILSP algorithms - Google Patents

Signal blind despread method based on ILSP algorithms Download PDF

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Publication number
CN107342786A
CN107342786A CN201710531404.7A CN201710531404A CN107342786A CN 107342786 A CN107342786 A CN 107342786A CN 201710531404 A CN201710531404 A CN 201710531404A CN 107342786 A CN107342786 A CN 107342786A
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matrix
ilsp
algorithms
user
signal
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CN107342786B (en
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张花国
曾辉
甘露
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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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]
    • 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
    • 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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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Noise Elimination (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention belongs to a kind of short code DS CDMA signal blind despread methods of blind despread technical field, more particularly to multipath transmisstion based on ILSP algorithms.The present invention is the synchronous short code DS CDMA signal blind despread methods propagated based on ILSP algorithms through multipath channel, by the synchronous short code DS CDMA signal modelings received into matrix form, then according to the special construction of information code matrix and ± 1 characteristic, receipt signal matrix are decomposed using ILSP algorithms, obtain the estimated matrix of the combined channel matrix of the Sequence composition obtained by user's frequency expansion sequence and channel parameter convolutionFinally de-spread to obtain user profile code matrix using combined channel matrix.Computer Simulation shows that the present invention still has preferable performance under Low SNR.

Description

Signal blind despread method based on ILSP algorithms
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 algorithms CDMA signal blind despread methods.
Background technology
DSSS (DSSS, the Direct Sequence Spread Spectrum) communication technology is outstanding due to its Anti-interference and anti-intercepting and capturing ability, be widely used in the civilian and military communications field, therefore there is very far-reaching practical valency Value and Research Significance.The DSSS communication technologys are when signal is sent, and are multiplied using the frequency expansion sequence of high-speed with information code sequence, So that the frequency spectrum of signal is widened, spectrum density reduces, and identical high speed sequence and is received in recipient, then during with sending Signal multiplication, the spectrum recovery of signal is set to complete despreading, and noise and the frequency spectrum of interference are expanded, spectrum density reduces, this Sample is just easy to filter out noise and interference from signal.For cooperation recipient, can with the frequency expansion sequence being known a priori by from The information code sequence transmitted is de-spread in reception signal, but is needed for non-cooperation recipient to the signal of reception Reason, therefrom extracts signal spread-spectrum sequence, and the frequency expansion sequence then obtained with estimation de-spreads to obtain transmission information code sequence.It is multi-purpose Family scene, each user use different spread spectrum code sequences, and obtained frequency expansion sequence now is DS-CDMA signals, in reality DS-CDMA signals are more widely applied in, therefore to the blind despread Research Significance of DS-CDMA signals bigger.
The content of the invention
It is an object of the invention to overcome the deficiencies in the prior art, it is proposed that a kind of signal blind despread based on ILSP algorithms Method, method proposed by the present invention are applied to the synchronous short code DS-CDMA signals blind despread problem propagated into multipath channel.
To realize the purpose of foregoing invention, the present invention comprises the following steps：
S1, the short code DS-CDMA signals through multipath transmisstion received are represented by Wherein, R represents 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, hrThe convolution sequence of spread spectrum code sequence and multi-path channel parameters for r-th user, n (n) is that variance is σ2Gauss White noise；
S2, the matrix form of short code DS-CDMA signals through multipath transmisstion are written as Y=HAST+ N, wherein, JR × JR dimensions pair Angular moment battle array A=diag (a1,…a1,……aR,…aR) it is signal amplitude matrix, J is the letter of the intersymbol interference caused by multipath Code number is ceased, L × JR dimension matrix Hs are that the frequency expansion sequence of R user and the sequences h after multi-path coefficients convolution and zero construction form Matrix, M × JR dimensions matrix S are the Toeplitz matrixes being configured to by the element of (M+J) × R dimension information code matrix Bs, and matrix N is The matrix form of noise in reception signal；
S3, for DS-CDMA signal matrix model Y, due to matrix S Toeplitz matrixes special construction and ± 1 characteristic, If the Toeplitz structures that fuzzy matrix can destroy matrix S be present, and matrix A is diagonal matrix, i.e., only can row production each to matrix H Raw yardstick influences, and only H each columns need to be normalized and can eliminated, therefore matrix Y is decomposed to obtain S using ILSP algorithms The estimated matrix of matrix and H-matrixWithIt is specific as follows：
S31, make i=0, random initializtion (M+J) × R dimension matrixesAnd by matrixObtain Toeplitz form squares Battle array
S32, i=i+1 is made, calculated 1≤r≤R, eliminating yardstick influences；
S33, calculatingBy matrixObtain information code matrixAgain by matrixObtain Toeplitz formal matrices
S34, repetition S32-S33 until algorithmic statement or reach maximum iteration, wherein, the condition of algorithmic statement isε is convergent threshold value, ε=1 × 10-9, the maximum iteration is 50 times；
S4, the estimated matrix with the H-matrix finally givenDe-spread to obtain the estimated matrix of information matrix s-matrix
Further, S31-S34 is repeated, be i.e. repeatedly ILSP algorithms Q times, selects iteration effect is best to be once used as finally As a result, wherein, Q is the natural number being not zero.
Further, S31-S34 is repeated, be i.e. repeatedly ILSP algorithms algorithm 40 times, selects the best once work of iteration effect For final result.
The beneficial effects of the invention are as follows：
The present invention is the synchronous short code DS-CDMA signals blind despread method propagated based on ILSP algorithms through multipath channel, will The synchronous short code DS-CDMA signal modelings received are then special according to the special construction of information code matrix and ± 1 into matrix form Property, receipt signal matrix are decomposed using ILSP algorithms, obtain what is obtained by user's frequency expansion sequence and channel parameter convolution The estimated matrix of the combined channel matrix of Sequence compositionFinally de-spread to obtain user profile code square using combined channel matrix Battle array.Computer Simulation shows that the present invention still has preferable performance under Low SNR.
Brief description of the drawings
Fig. 1 is that one kind of the short code DS-CDMA signal blind despread methods of the invention based on ILSP algorithm multipath transmisstions 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 The poor change curve with signal to noise ratio.
Embodiment
The present invention will be described below in conjunction with the accompanying drawings.
Embodiment 1,
This purpose implemented is that the information code matrix bit error rate of different user number is emulated with signal to noise ratio change, Fig. 1 is a kind of specific embodiment party of the synchronous short code DS-CDMA signal through multipath channel propagated of the present invention based on ILSP algorithms Formula flow chart.As shown in figure 1, the present invention realizes the synchronous short code DS-CDMA signal blind despreads method of multipath transmisstion including following Step：
Step 1：The short code DS-CDMA signals through multipath transmisstion received are represented by
Wherein, R represents the number of user, and this is embodied as R=3 and R=4, arFor the signal amplitude of r-th of user, sheet It is random number in secondary implementation, brFor 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, and this implements M=100, spreading gain L=31, and the multi-path channel parameters of individual user are all [1,0.9,0.7,0.5,0.3,0.15], hrThe convolution sequence of spread spectrum code sequence and multi-path channel parameters for r-th user, n (n) it is that variance is σ2White Gaussian noise.
Step 2：From step 1, the matrix form of the short code DS-CDMA signals through multipath transmisstion can be written as
Y=HAST+N
Wherein JR × JR dimension 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 dimension matrix Hs are the frequency expansion sequence and multi-path coefficients convolution of R user The matrix that sequences h and zero construction afterwards forms, M × JR dimensions matrix S are configured to by the element of (M+J) × R dimension information code matrix Bs Toeplitz matrixes, matrix N be reception signal in noise matrix form.
The information code matrix of unique userStructure be shown below
Step 3：For the DS-CDMA signal matrix model Y of above-mentioned introduction, because matrix S Toeplitz matrixes are special Structure and ± 1 characteristic, if the Toeplitz structures that fuzzy matrix can destroy matrix S be present, and matrix A is diagonal matrix, i.e., only It each on matrix H can arrange and produce yardstick influence, only H each columns need to be normalized and can eliminated, therefore we can be direct Matrix Y is decomposed using ILSP algorithms to obtain the estimated matrix of s-matrix and H-matrixWith
Implement step：
Make i=0, random initializtion (M+J) × R dimension matrixesAnd by matrixObtain Toeplitz formal matrices
I=i+1 is made, is calculated 1≤r≤R, eliminating yardstick influences；
CalculateBy matrixObtain information code matrixAgain by matrixObtain Toeplitz shapes Formula matrix
Repeat step (2)~(3) are until algorithmic statement or reach maximum iteration, and the condition of algorithmic statement is
Wherein, ε is convergent threshold value, is usually taken to be 1 × 10-9, in the method, maximum iteration is set to 50.
In order to improve algorithm performance, repeat step (1)~(4) repeatedly (this method elects 40 as), select iteration effect best Be once used as final result.
Step 4：With the estimated matrix of the H-matrix finally givenDe-spread to obtain the estimation square of information matrix s-matrix Battle array
Obtained estimated matrix is compared with former data matrix, count the bit error rate, while with the conjunction under same case Contrasted that (during cooperative communication, combined channel matrix H is, it is known that by formula S=sign (H as communication-1Y user can) be tried to achieve 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 curves.As can be seen from the figure blind solution proposed by the present invention Expanding method is functional in the case of 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 the normalized mean squared error rate to combining channel matrix under the conditions of different user number Emulated with SNR (Signal Noise Rate, signal to noise ratio) changes.It is R=3 and R=4 that this, which implements user's number, and its Its condition is identical with implementing 1, and the normalized mean squared error of combined channel is calculated by following formula：
1000 Monte Carlo experiments are carried out, the combined channel matrix normalization mean square error finally given 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 the case of 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., gradual approaching to reality value, is consistent with theory.

Claims (3)

  1. A kind of 1. signal blind despread method based on ILSP algorithms, it is characterised in that comprise the following steps：
    S1, the short code DS-CDMA signals through multipath transmisstion received are represented by Wherein, R represents 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, hrThe convolution sequence of spread spectrum code sequence and multi-path channel parameters for r-th user, n (n) is that variance is σ2Gauss White noise；
    S2, the matrix form of short code DS-CDMA signals through multipath transmisstion are 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 code of the intersymbol interference caused by multipath Number, L × JR dimension matrix Hs are the square that the frequency expansion sequence of R user forms with the sequences h after multi-path coefficients convolution and zero construction Battle array, M × JR dimensions matrix S are the Toeplitz matrixes being configured to by the element of (M+J) × R dimension information code matrix Bs, 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 matrix S Toeplitz matrixes special construction and ± 1 characteristic, if depositing Matrix S Toeplitz structures can be destroyed in fuzzy matrix, and matrix A is diagonal matrix, i.e., only can row generation chi each to matrix H Degree influences, and only H each columns need to be normalized and can eliminated, therefore matrix Y is decomposed to obtain s-matrix using ILSP algorithms With the estimated matrix of H-matrixWithIt is specific as follows：
    S31, make i=0, random initializtion (M+J) × R dimension matrixesAnd by matrixObtain Toeplitz formal matrices
    S32, i=i+1 is made, calculatedEliminating yardstick influences；
    S33, calculatingBy matrixObtain information code matrixAgain by matrixObtain Toeplitz shapes Formula matrix
    S34, repetition S32-S33 until algorithmic statement or reach maximum iteration, wherein, the condition of algorithmic statement isε is convergent threshold value, ε=1 × 10-9, the maximum iteration is 50 times；
    S4, the estimated matrix with the H-matrix finally givenDe-spread to obtain the estimated matrix of information matrix s-matrix
  2. A kind of 2. signal blind despread method based on ILSP algorithms according to claim 1, it is characterised in that：Repeat S31- S34, i.e. repeatedly ILSP algorithms Q times, select iteration effect it is best be once used as final result, wherein, Q is the nature being not zero Number.
  3. A kind of 3. signal blind despread method based on ILSP algorithms according to claim 1 or 2, it is characterised in that：Repeat S31-S34, i.e. repeatedly ILSP algorithms algorithm 40 times, select iteration effect it is best be once used as final result.
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Citations (3)

* Cited by examiner, † Cited by third party
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

Patent Citations (3)

* Cited by examiner, † Cited by third party
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)

* Cited by examiner, † Cited by third party
Title
HUAGUO ZHANG等: "A Semidefinite Relaxation Approach to Blind Despreading of Long-Code DS-SS Signal With Carrier Frequency Offset", 《IEEE SIGNAL PROCESSING LETTERS》 *
HUAGUO ZHANG等: "Blind synchronization algorithm for the DS-CDMA signals", 《2009 INTERNATIONAL CONFERENCE ON COMMUNICATIONS, CIRCUITS AND SYSTEMS》 *
张花国，李鑫: "一种改进的异步CDMA信号的盲解扩算法", 《电子技术应用》 *

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