CN107294560B - Asynchronous short code DS-CDMA signal blind despread method - Google Patents

Asynchronous short code DS-CDMA signal blind despread method Download PDF

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CN107294560B
CN107294560B CN201710531403.2A CN201710531403A CN107294560B CN 107294560 B CN107294560 B CN 107294560B CN 201710531403 A CN201710531403 A CN 201710531403A CN 107294560 B CN107294560 B CN 107294560B
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matrix
user
cdma signal
short code
code
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CN107294560A (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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    • 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
    • H04B1/70718—Spread spectrum techniques using direct sequence modulation with asynchronous demodulation, i.e. not requiring code synchronisation

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
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Abstract

The invention belongs to blind despread technical field more particularly to a kind of asynchronous short code DS-CDMA signal blind despread methods based on ILSP algorithm.The present invention is based on the asynchronous short code DS-CDMA signal blind despread method of ILSP algorithm, by the asynchronous 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 is decomposed using ILSP algorithm, obtain estimated matrixIt 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

Asynchronous short code DS-CDMA signal blind despread method
Technical field
The invention belongs to blind despread technical field more particularly to a kind of asynchronous short code DS-CDMA letters based on ILSP algorithm Number 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 asynchronous blind solution of short code DS-CDMA signal Expanding method, method proposed by the present invention are suitable for asynchronous short code DS-CDMA signal blind despread problem.
For realize foregoing invention purpose, the present invention the following steps are included:
S1, asynchronous short code DS-CDMA signal each subscriber signal arrival time difference, that is, each user delay it is different, Therefore the asynchronous short code DS-CDMA signal that non-cooperation receiving end receives is expressed as after chip rate samplesWherein, R indicates user's number, and N is signal sample This length is the signal amplitude of user r, τrIndicate the propagation delay time of r-th of user, η (n) indicates that variance is σ2Gauss white noise Sound, M are asynchronous short code DarInformation code number in S-CDMA signal, srIndicate the information code sequence of user r, L indicates spread spectrum sequence The period of column, crIndicate the spread spectrum code sequence of user r；
S2, asynchronous short code DS-CDMA signal matrix form can be written as Y=HASTThe submatrix block S of+N, user rrAnd Hr Structure beWherein, 2R × 2R is tieed up Diagonal matrix A=diag (a1,a1,……aR,aR), L × 2R ties up L × 2R dimensional expansion frequency sequence Matrix C structure that matrix H is R user Matrix made of making, M × 2R dimension matrix S are by the element construction of (M-1) × R dimension information code matrix B, and matrix N is noise matrix；
S3, the DS-CDMA signal matrix model for above-mentioned introduction, since matrix S structure is special and ± 1 characteristic of element, And matrix A is diagonal matrix and can be included into matrix H, directlying adopt ILSP algorithm decomposes to obtain s-matrix, implements step It is as follows:
S31, i=0, random initializtion M × 2R is enabled to tie up matrix
S32, i=i+1 is enabled, calculated
S33, calculating
S34, repetition S32-S33 until algorithmic statement or reach maximum number of iterations, and the condition of algorithmic statement isWherein, ε is convergent threshold value, ε=1 × 10-9, maximum number of iterations is set as 50；
S4, the estimated matrix for obtaining spreading code matrix HThe matrix obtained by estimationDespreading obtains user information code square The estimated matrix of battle array
Further, in order to improve algorithm performance, S1-S34Q times (this method is selected as 40) is repeated, selects τ the smallest primary As final result, wherein Q is the natural number being not zero.
Further, it in order to improve algorithm performance, repeats S1-S34Q=40 times, selects τ the smallest primary as most terminating Fruit.
The beneficial effects of the present invention are:
The present invention is the asynchronous short code that will be received based on the asynchronous short code DS-CDMA signal blind despread method of ILSP algorithm DS-CDMA signal modeling, then according to the special construction of information code matrix and ± 1 characteristic, utilizes ILSP algorithm at matrix form Receipt signal matrix are decomposed, estimated matrix is obtainedIt finally de-spreads to obtain user information code using combined channel matrix Matrix.Even if Computer Simulation shows that the present invention still has preferable performance under Low SNR
Detailed description of the invention
Fig. 1 is a kind of specific implementation of the asynchronous short code DS-CDMA signal blind despread method the present invention is based on ILSP algorithm Mode flow chart.
Fig. 2 is in present invention specific implementation, and the bit error rate of the information code Matrix Estimation matrix of different user number is with signal-to-noise ratio Change curve.
Specific embodiment
The present invention will be described with reference to the accompanying drawing.
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 flow chart of the asynchronous short code DS-CDMA signal the present invention is based on ILSP algorithm.Such as Fig. 1 institute Show, the present invention realize asynchronous short code DS-CDMA signal blind despread method the following steps are included:
Step 1: the asynchronous short code DS-CDMA signal received is represented by
Wherein, R indicates the number of user, this is embodied as R=2 and R=3, arFor the signal amplitude of r-th of user, sheet It is random number, s 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=30, spreading gain L=31, crIndicate the spread spectrum code sequence of user r.η It (n) be variance is σ2White Gaussian noise.
Step 2: by step 1 it is found that the matrix form of asynchronous short code DS-CDMA signal can be written as
Y=HAST+N
Wherein 2R × 2R ties up diagonal matrix A=diag (a1,a1,……aR,aR), L × 2R ties up the L that matrix H is R user Matrix made of × 2R dimensional expansion frequency sequence Matrix C construction, M × 2R dimension matrix S are by the element of (M-1) × R dimension information code matrix B Construction, matrix N is noise matrix.
The submatrix block S of single user rrAnd HrStructure be
Step 3: for the DS-CDMA signal matrix model of above-mentioned introduction, since matrix S structure is special and element ± 1 is special Property, and matrix A is diagonal matrix and can be included into matrix H, we can be directly used ILSP algorithm and decompose to obtain s-matrix.
Implement step:
(1) i=0, random initializtion M × 2R is enabled to tie up matrix
(2) i=i+1 is enabled, is calculated
(3) it calculates
(4) step (2)~(3) are repeated 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 this algorithm, maximum number of iterations is set as 50.
(5) in order to improve algorithm performance, step (1)~(4) is repeated repeatedly (this method is selected as 40), select effect preferably (τ It is minimum) primary be used as final result.
Step 4: obtaining the estimated matrix of spreading code matrix HThe matrix obtained by estimationDespreading obtains user information The estimated matrix of code matrix
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.

Claims (2)

1. a kind of asynchronous short code DS-CDMA signal blind despread method, which comprises the steps of:
S1, asynchronous short code DS-CDMA signal each subscriber signal arrival time difference, that is, each user delay it is different, therefore The asynchronous short code DS-CDMA signal that non-cooperation receiving end receives is expressed as after chip rate samplesWherein, R indicates user's number, and N is signal Sample length, arFor the signal amplitude of user r, τrIndicate the propagation delay time of r-th of user, η (n) indicates that variance is σ2Gauss White noise, M are the information code number in asynchronous short code DS-CDMA signal, srIndicate the information code sequence of user r, L indicates spread spectrum Gain, crIndicate the spread spectrum code sequence of user r；
S2, asynchronous short code DS-CDMA signal matrix form can be written as Y=HASTThe knot of submatrix the block Sr and Hr of+N, user r Structure isWherein, 2R × 2R ties up diagonal matrix A= diag(a1,…,a1,……aR,…aR), L × 2R dimension matrix H is that L × 2R dimensional expansion frequency sequence Matrix C of R user constructs Matrix, M × 2R dimension matrix S be by (M-1) × R dimension information code matrix B element construction, matrix N is noise matrix；
S3, the DS-CDMA signal matrix model for above-mentioned introduction, since matrix S structure is special and ± 1 characteristic of element, and square Battle array A is diagonal matrix and can be included into matrix H, directlys adopt ILSP algorithm and decomposes to obtain s-matrix, specific implementation step is such as Under:
S31, i=0, random initializtion M × 2R is enabled to tie up matrix
S32, i=i+1 is enabled, calculated
S33, calculating
S34, repetition S32-S33 until algorithmic statement or reach maximum number of iterations, and the condition of algorithmic statement isWherein, ε is convergent threshold value, ε=1 × 10-9, maximum number of iterations is set as 50；
S4, the estimated matrix for obtaining spreading code matrix HThe matrix obtained by estimationDespreading obtains user information code matrix Estimated matrix
2. a kind of asynchronous short code DS-CDMA signal blind despread method according to claim 1, it is characterised in that: repeat S1- S34Q=40 times, select τ the smallest primary as final result.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103414670A (en) * 2013-08-21 2013-11-27 电子科技大学 Long code DSSS signal blind dispreading method based on semi-definite programming
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

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Publication number Priority date Publication date Assignee Title
US8374219B2 (en) * 2009-11-23 2013-02-12 Telefonaktiebolaget L M Ericsson (Publ) Blind spreading factor detection for wideband code division multiple access (WCDMA)

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
CN103414670A (en) * 2013-08-21 2013-11-27 电子科技大学 Long code DSSS signal blind dispreading method based on semi-definite programming
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

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《一种改进的异步CDMA信号的盲解扩算法》;张花国等;《电子技术应用》;20151010;第41卷(第10期);第77-80页 *

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