CN107070497B - A kind of spread spectrum communication multi-address interference supression method about subtracted based on lattice - Google Patents
A kind of spread spectrum communication multi-address interference supression method about subtracted based on lattice Download PDFInfo
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- 238000001228 spectrum Methods 0.000 title claims abstract description 31
- 238000004891 communication Methods 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims abstract description 13
- 239000011159 matrix material Substances 0.000 claims abstract description 39
- 238000004422 calculation algorithm Methods 0.000 claims abstract description 35
- 238000001514 detection method Methods 0.000 claims abstract description 34
- 230000009467 reduction Effects 0.000 claims abstract description 20
- 230000009466 transformation Effects 0.000 claims abstract description 20
- 238000013139 quantization Methods 0.000 claims abstract description 11
- 238000005457 optimization Methods 0.000 claims abstract description 10
- 230000001629 suppression Effects 0.000 claims description 10
- 238000012545 processing Methods 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 4
- 230000008030 elimination Effects 0.000 claims description 3
- 238000003379 elimination reaction Methods 0.000 claims description 3
- 238000010606 normalization Methods 0.000 claims description 3
- 230000005540 biological transmission Effects 0.000 abstract 1
- 238000005516 engineering process Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 3
- 230000007480 spreading Effects 0.000 description 3
- 238000007476 Maximum Likelihood Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
- 238000011426 transformation method Methods 0.000 description 1
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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
- H04B1/71052—Joint detection techniques, e.g. linear detectors using decorrelation matrix
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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
- H04B1/709—Correlator structure
- H04B1/7093—Matched filter type
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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
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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
- H04B1/71055—Joint detection techniques, e.g. linear detectors using minimum mean squared error [MMSE] detector
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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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Abstract
The invention discloses a kind of spread spectrum communication multi-address interference supression methods about subtracted based on lattice, are related in spread spectrum communication system, and there are when multipath spread-spectrum signal, signal receiving end carries out spread-spectrum signal and receives demodulation.Include: one, multipath spread-spectrum signal is subjected to signal estimation, obtains the estimated value of multiple signals；Two, the cross-correlation matrix between signal is obtained using local pseudo-code；Three, transformation matrix and optimization matrix are obtained using lattice reduction algorithm；Four, the joint-detection of signal is carried out using multiuser detection algorithm；Five, quantization is modified to obtained joint detection results；Six, final joint detection results are obtained using transformation matrix.The present invention effectively eliminates multi-access inference caused by the transmission of multipath spread-spectrum signal parallel with lower computational complexity, the demodulation bit error rate of multipath spread-spectrum signal is greatly lowered, can under severe multiple access environments approximation theory optimal detection performance, biggish performance advantage is shown in terms of near far resistance.
Description
Technical Field
The invention relates to a spread spectrum communication multiple access interference suppression method, in particular to a spread spectrum communication multiple access interference suppression method based on lattice reduction.
Background
Spread spectrum communication has been widely used in the fields of satellite communication, satellite navigation, military and civil communication, etc. because of its characteristics of large capacity, anti-interference, etc. As a self-interference scheme, its communication capability and application are limited by the multiple access interference problem. In a civil ground mobile communication system, multiple access interference can be effectively inhibited by adopting technical means such as zero correlation spread spectrum codes and intelligent antennas, but in such spread spectrum communication systems as military communication and satellite communication, the problem of multiple access interference can be solved only by optimizing signal system design to a certain extent, multiple access interference inhibition technology is required to be adopted at a signal receiving end to realize maximization of communication capacity, and the traditional technology comprises two types of multi-user detection and multiple access interference elimination.
The main problems of the existing multiple access interference suppression technology are as follows: the multi-user detection algorithm has better multi-access interference suppression performance, but the detection performance is poorer under the severe near-far effect condition; the performance of the multi-access interference elimination method is limited by the initial detection accuracy of multi-user signals, and compared with the performance of a multi-user detection algorithm, the performance is poor, particularly, the platform effect occurs earlier under the condition of worse multi-access interference, and the multi-access interference suppression performance is not ideal.
Disclosure of Invention
The invention aims to avoid the defects in the background technology, introduces the lattice reduction theory into spread spectrum communication multi-user detection, and provides a spread spectrum communication multi-user detection method based on the lattice reduction. The invention realizes the orthogonal optimization of the cross-correlation matrix through the lattice reduction transformation, improves the error rate performance of the multi-user joint detection algorithm, and particularly can obtain better multi-access interference suppression performance under severe multi-access conditions.
The invention aims to realize the method for suppressing the multiple access interference of spread spectrum communication based on lattice reduction, which is used for a signal receiving end to eliminate the multiple access interference of spread spectrum signals and demodulate the signals when multiple paths of spread spectrum signals exist in a spread spectrum communication system and comprises the following steps:
① processing the multi-path spread spectrum signals by a matched filter bank to obtain the estimated values of the multi-path signals, and processing the estimated values of the multi-path signals respectively to obtain the signal power, the relative time delay between the signals and the carrier phase difference of each path of signals;
②, based on the signal power, the relative time delay and the carrier phase difference of each path of signal, obtaining the cross correlation matrix of the signals by using the local pseudo code;
③, carrying out lattice reduction processing on the cross-correlation matrix by using a lattice reduction algorithm to obtain a transformation matrix and an optimization matrix;
④, performing joint detection of signals by using a multi-user joint detection algorithm based on the transformation matrix and the optimization matrix;
⑤ correcting and quantifying the obtained joint detection result in the optimized lattice point space;
⑥ the final estimation result is obtained by using the modified quantization result and the transformation matrix.
Wherein, the multi-user joint detection algorithm in the step ④ is a ZF algorithm or an MMSE algorithm, and the calculation formula is as follows:
ZF algorithm joint detection resultComprises the following steps:
joint detection result by using MMSE algorithmComprises the following steps:
in the formula sigma2For the noise variance, Y is the estimated value of the multipath signal obtained from step ①, H' is the optimization matrix obtained in step ③, and P is the transformation matrix obtained in step ③.
Wherein, the formula of the modified quantization in step ⑤ is:
wherein,for correcting the quantization result, the term "is rounded, I is the unit column vector, a is the energy normalization parameter, and P is the transformation matrix.
The calculation formula of the final estimation result in step ⑥ is:
in the formula,in order to be the final result of the estimation,to modify the quantization result, P is the transform matrix.
Compared with the background technology, the invention has the following advantages:
(i) the invention reduces the correlation among signals by the lattice reduction transformation of the multi-user signal cross-correlation matrix, and realizes the performance of the maximum likelihood algorithm approaching the theoretical optimum with lower operation complexity by combining the multi-user detection algorithm.
(ii) The algorithm provided by the invention can keep approaching to the performance of the maximum likelihood detection algorithm in a severe multiple access environment, and compared with the traditional multi-user detection algorithm, the performance is greatly improved, and the algorithm has excellent performance in the aspect of resisting the near-far effect.
Drawings
Fig. 1 is a flow chart of the lattice reduction assisted multiple access interference suppression algorithm of the present invention.
Detailed Description
The invention will be further described with reference to specific embodiments and the accompanying drawings in which:
the method of the invention has a flow chart as shown in fig. 1, and specifically comprises the following steps:
step 101: the receiving end receives the multi-channel spread spectrum signals, carries out signal estimation on each channel of signals through a matched filter group to obtain estimated values of the multi-channel signals, and processes the estimated values of the multi-channel signals respectively to obtain signal power, relative time delay among the signals and carrier phase difference of each channel of signals;
the received multipath spread spectrum signals are:
where A is the signal amplitude and b is the information bitPN is signal spread code, N is background noise, k represents k path spread signal, N is path number of spread signal, TbIs the bit duration.
The discrete-time output of the matched filter for the kth spread spectrum signal is:
in the formula ykTerm 1 of (a) is coherent accumulation of the desired signal; term 2 is the cumulative sum of the cross-correlations of the other signals with the spreading code of the desired signal; term 3 is the correlated interference, p, of the channel noise with the desired signalkjThe cross-correlation between the spreading code of the k-th signal and the spreading code of the i-th signal is obtained.
The estimated values output by the matched filter of the N paths of spread spectrum signals are as follows:
Y＝[y1,y2,…yN]T；
step 102: based on the signal power, the relative time delay and the carrier phase difference of each path of signal, obtaining a cross-correlation composite matrix H between the signals by using a local pseudo code;
and calculating a matrix R by using each path of pseudo code generated locally.
The signal amplitude matrix is
The cross-correlation matrix is H ═ RA.
Step 103: carrying out lattice reduction processing on the cross-correlation matrix by using a lattice reduction algorithm such as LLL (Linear Log-Log) or Seysen algorithm;
and carrying out lattice reduction transformation on H, wherein the transformation method can adopt LLL, Seysen or other lattice reduction strategies. And obtaining an optimized matrix H' ═ HP through lattice reduction transformation, and P is a transformation matrix.
Step 104: performing joint detection on signals by using a multi-user joint detection algorithm based on the transformation matrix and the optimization matrix;
the multi-user joint detection algorithm comprises a ZF algorithm or an MMSE algorithm and the like; the calculation formula is as follows:
ZF algorithm joint detection resultComprises the following steps:
MMSE algorithm joint detection resultComprises the following steps:
in the formula sigma2And Y is the estimated value of the multipath signal, H' is an optimization matrix, and P is a transformation matrix.
Step 105: to the obtainedIn the optimized lattice point spacePerforming correction quantization to correct the quantization resultComprises the following steps:
where "represents rounding, I is the unit column vector, and a is the energy normalization parameter.
Step 106: byThe final estimation result can be obtained
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions which adopt equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (4)
1. A spread spectrum communication multiple access interference suppression method based on lattice reduction is used for a signal receiving end to carry out spread spectrum signal multiple access interference elimination and signal demodulation when multiple paths of spread spectrum signals exist in a spread spectrum communication system, and is characterized by comprising the following steps:
①, carrying out signal estimation on the multi-path spread spectrum signals through a matched filter bank to obtain estimated values of the multi-path signals, and respectively processing the estimated values of the multi-path signals to obtain the signal power, the relative time delay between the signals and the carrier phase difference of each path of signals;
②, based on the signal power, the relative time delay and the carrier phase difference of each path of signal, obtaining the cross correlation matrix of the signals by using the local pseudo code;
③, carrying out lattice reduction processing on the cross-correlation matrix by using a lattice reduction algorithm to obtain a transformation matrix and an optimization matrix;
④, performing joint detection of signals by using a multi-user joint detection algorithm based on the transformation matrix and the optimization matrix;
⑤ correcting and quantifying the obtained joint detection result in the optimized lattice point space;
⑥ obtaining final estimation result by using the modified quantization result and the transformation matrix;
and completing the spread spectrum communication multiple access interference suppression algorithm based on the lattice reduction.
2. The method as claimed in claim 1, wherein the multiuser joint detection algorithm in step ④ is ZF algorithm or MMSE algorithm, and the calculation formula is:
ZF algorithm joint detection resultComprises the following steps:
MMSE algorithm joint detection resultComprises the following steps:
in the formula sigma2For the noise variance, Y is the estimated value of the multipath signal obtained in step ①, H' is the optimization matrix obtained in step ③, and P is the transformation matrix obtained in step ④.
3. The method of claim 1 wherein the formula for modifying the quantization in step ⑤ is:
wherein,for correcting the quantization result, "" indicates rounding, I is the unit column vector, a is the energy normalization parameter, P is the transformation matrix,is the combined detection result.
4. The method of claim 1 wherein the final estimate of step ⑥ is calculated by the formula:
in the formula,in order to be the final result of the estimation,to modify the quantization result, P is the transform matrix.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101675598A (en) * | 2007-06-08 | 2010-03-17 | Lm爱立信电话有限公司 | Reduced lattice demodulation method and apparatus |
| CN102185630A (en) * | 2011-04-13 | 2011-09-14 | 中兴通讯股份有限公司 | Narrowband interference suppression method and device used in spread spectrum communication system and receiver |
| CN102647220A (en) * | 2012-03-23 | 2012-08-22 | 北京邮电大学 | A Control Method of Multiple Input Multiple Output Precoding Based on Lattice Reduction |
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| US7593481B2 (en) * | 1998-08-31 | 2009-09-22 | Kamilo Feher | CDMA, W-CDMA, 3rd generation interoperable modem format selectable (MFS) systems with GMSK modulated systems |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101675598A (en) * | 2007-06-08 | 2010-03-17 | Lm爱立信电话有限公司 | Reduced lattice demodulation method and apparatus |
| CN102185630A (en) * | 2011-04-13 | 2011-09-14 | 中兴通讯股份有限公司 | Narrowband interference suppression method and device used in spread spectrum communication system and receiver |
| CN102647220A (en) * | 2012-03-23 | 2012-08-22 | 北京邮电大学 | A Control Method of Multiple Input Multiple Output Precoding Based on Lattice Reduction |
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