CN103841065B  Nonopiate multiple access is sent and joint receives demodulation coding system and method  Google Patents
Nonopiate multiple access is sent and joint receives demodulation coding system and method Download PDFInfo
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 CN103841065B CN103841065B CN201410053191.8A CN201410053191A CN103841065B CN 103841065 B CN103841065 B CN 103841065B CN 201410053191 A CN201410053191 A CN 201410053191A CN 103841065 B CN103841065 B CN 103841065B
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Abstract
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Technical field
Nonopiate multiple access is sent and joint receives demodulation coding system and method and belongs to field of communication technology, especially The joint reception demodulation for being related to a kind of nonopiate multiple access in multiuser comm and elimination interuser interference is translated Code System and method for.
Background technology
In order to reduce cost and efficiently utilize the resource of communication system, existing communication system generally uses CDMA (Code Division Multiple Access, CDMA), interlacing multiaddress (Interleaver Division Multiple Access, IDMA) etc. nonopiate access way distinguish different users, with the increase of number of users, interuser interference meeting Increase, so as to the hydraulic performance decline of entire communication system.
The traditional methods for eliminating multiuser interference are to regard interuser interference as additive noise, separately detect each The information of a user, system performance are severely limited by interference.Another kind of method is Multiuser Detection, no longer by interference at noise Reason, but the information with certain structure is considered as, specifically using the correlation properties between address code, inhibit even to eliminate The influence of multiaccess inference.
It is whether linear according to algorithm, existing multiuser detection algorithm can be divided into Linear Multiuser Detection algorithm and non Linear Multiuser Detection algorithm.Linear Multiuser Detection algorithm is to make a line to the output vector y of traditional matched filter Property operation L, to eliminate the influence of multiaccess inference.This method is related to matrix inversion operation, and computation complexity is usually higher. The basic thought of MultiUser Detection algorithm is that interference is eliminated, that is, subscriber signal after testing is reconstructed, by it from reception Other users are detected again after being eliminated in signal.This method can cause the propagation of error, bring larger delay.
The present invention proposes nonopiate multiple access and sends and combine reception demodulation coding system and method.The algorithm Main thought is in transmitting terminal, and multiple users use nonorthogonal manner access system, in receiving terminal, based on message transmission thought, The output Soft Inform ation of decoder is sent directly into Multiuser Detection, realizes that decoding and the Joint iteration of Multiuser Detection are handled. Under linear computation complexity, the present invention can realize good interference elimination performance.
Invention content
It is sent the object of the present invention is to provide nonopiate multiple access and joint receives demodulation coding system and method. Transmitting terminal, multiuser are accessed using nonorthogonal manner, in receiving terminal, using message passing mechanism, realize that decoding is examined with multiuser The Joint iteration processing of survey.The present invention is suitable for the multiuser comm of nonopiate access, is done between user the purpose is to reduce It disturbs, improves the performance of transmission.
Nonopiate multiple access is sent and joint receives demodulation coding system, which is characterized in that it is divided into two big systems, one It is the nonopiate access of multiuser and transmission system, first, the joint of multiple user signals receives demodulation coding system, wherein:
(1) the nonopiate access of multiuser and transmission system, equipped with channel coding module, coded identification mapping block, interweave Module and modulation module, wherein：
Channel coding module：To the information sequence b of kth of user_{k}Carry out channel coding, k=1,2 ..., K, by channel Output sequence c after coding_{k}, L is sequence c after coding_{k}Length；
Coded identification mapping block：The sequence c_{k}In each symbol be each mapped to the feature that length is N Sequence p_{k}, N is natural number more than or equal to 1, p_{k}={ z_{1},z_{2},...,z_{N}, z_{i}∈ { 1, 1 }, i=1,2 ..., N, i are characterized The serial number of parameter z, N are characterized the number of parameter, and the mapping ruler of symbol is according to 1 → p_{k}, 0 →p_{k}, map postorder and be classified as r_{k}；
Interleaving block：The sequence r of input_{k}It is interleaved, obtains sequence v_{k}；
Modulation module：The sequence v of input_{k}It is modulated, obtains sequence u_{k}, it is sent to receiving terminal；
(2) joint of multiple user signals receives demodulation coding system, is equipped with：Multiuser detection module, demodulation reconciliation Interleaving block and decoding module：
First by the reception sequences y of kth of user_{k}[n] is multiplied by the characteristic sequence p of each user symbolbysymbol_{k}, obtain kth The observer nodes of userWherein K be user number, k=1,2 ..., K, n be each symbol the time of reception, n=1, 2 ..., N', N'=NL, L be coding after sequence c_{k}Length, N is characterized sequence p_{k}Length, l=1,2 ..., L, willAs the input of multiuser detection module, into iterative process；
Multiuser detection module is detected according to following steps：
A is initialized, setting：T is iterations, and t is current iteration number, t=1,2 ..., T, i=1,2 ..., K, j =1,2 ..., K, K be user number, when initial, by ith of user moment n symbol node x_{i}[n] is to jth of user Observer nodesThe message of transmissionIn x_{i}It is during [n]=1In x_{i}It is during [n]= 1
B is calculated in the t times iterative process by the symbol node x of ith of user_{i}[n] is to the observer nodes of jth of userThe message of transmission
It represents to remove ith and jth of user, remaining the 1 to kth user's The continued product of message that observer nodes are transmitted to the symbol node of ith of user,
C is calculated respectively according to above formulaMean valueAnd variance
Wherein, α_{i}It represents to send assemble of symbol { 1,1 },
D calculates the observer nodes of jth of user in the t times iterative processTo the symbol node x of ith of user_{i} [n] transmits the mean value of messageAnd variance
WhereinRepresent the observer nodes of jth of userWith the symbol node x of ith of user_{i}Between [n] Equivalent channel gain, σ^{2}Represent the variance of white Gaussian noise,
E, based on abovementioned mean valueAnd varianceUsing Gaussian approximation, calculate in the t times iteration In the process, the observer nodes of jth of userTo the symbol node x of ith of user_{i}The message that [n] is transmitted
The content of exp expressions below is the finger of e Number, andIt represents in the t times iterative process between the observer nodes of jth user and the symbol node of ith of user Equivalent channel gain,
Demodulation deinterleaving block：According toIth of user in the t times iterative process is calculated Symbol node x_{i}[n] is to the input node of decoderThe message of transmission
Wherein, n=1,2 ..., N', N'=NL, l=1,2 ..., L,
According to above formula, the input message of decoder is further obtained
" dec " is writing a Chinese character in simplified form for decoder decoder,Represent the input node from decoderIt is passed to decoder,
Decoding module：By the input node of the decoderThe message transmitted to decoder is mapped as loglikelihood ratio Form, judgement obtains the information bit sequence of corresponding each user
Abovementioned Multiuser Detection module is repeated between decoding module the step of until t=T；
Wherein：
The nonopiate multiple access is sent and joint reception demodulation coding system, in channel coding module, coding Mode is using any one of convolutional code, LDPC code, Turbo code, Turbo product codes.
The nonopiate multiple access is sent and joint reception demodulation coding system, and in modulation module, use is orthogonal The modulation of any one of amplitude modulation (QAM), four phase shift keying signal (QPSK), multisystem digital phase modulation (MPSK) Mode.
The nonopiate multiple access is sent and joint reception demodulation coding system, in interleaving block, using grouping One kind in interleaver, convolutional deinterleaver or random interleaver.
Nonopiate multiple access is sent and joint receives demodulation coding method, is divided into two big steps, first, multiuser is non Orthogonal access and transmission, first, the joint of multiple user signals receives demodulation coding:
(1) the nonopiate access of multiuser and forwarding step specifically include channel coding, coded identification mapping, interweave and adjust System, transmitting terminal is to each user by step operation in detail below：
Channel coding：To the information sequence b of kth of user_{k}Carry out channel coding, k=1,2 ..., K, by channel coding Output sequence c afterwards_{k}, L is sequence c after coding_{k}Length；
Coded identification maps：The sequence c_{k}In each symbol be each mapped to the characteristic sequence that length is N p_{k}, N is natural number more than or equal to 1, p_{k}={ z_{1},z_{2},...,z_{N}, z_{i}∈ { 1, 1 }, i=1,2 ..., N, i are characterized parameter The serial number of z, N are characterized the number of parameter, and the mapping ruler of symbol is according to 1 → p_{k}, 0 →p_{k}, map postorder and be classified as r_{k}；
Interweave：The sequence r of input_{k}It is interleaved, obtains sequence v_{k}；
Modulation：The sequence v of input_{k}It is modulated, obtains sequence u_{k}, it is sent to receiving terminal；
(2) multiple user signals joint receive demodulation coding step, including multiuser detection, demodulation deinterleave, Decoding：
First by the reception sequences y of kth of user_{k}[n] is multiplied by the characteristic sequence p of each user symbolbysymbol_{k}, obtain kth The observer nodes of userWherein K be user number, k=1,2,3 ..., K, n be each symbol the time of reception, n= 1,2 ..., N', N'=NL, L be coding after sequence c_{k}Length, N is characterized sequence p_{k}Length, l=1,2 ..., L, It willAs the input of multiuser detection module, into iterative process；
Multiuser detection, according to following steps：
A is initialized, setting：T is iterations, and t is current iteration number, t=1,2 ..., T, i=1,2 ..., K, j =1,2 ..., K, K be user number, when initial, by ith of user moment n symbol node x_{i}[n] is to jth of user Observer nodesThe message of transmissionIn x_{i}It is during [n]=1In x_{i}It is during [n]= 1
B is calculated in the t times iterative process by the symbol node x of ith of user_{i}[n] is to the observer nodes of jth of userThe message of transmission
It represents to remove ith and jth of user, remaining the 1 to kth user's The continued product of message that observer nodes are transmitted to the symbol node of ith of user, symbol " Π " represent even to multiply, and p represents certain in K A user, symbol " ∩ " represent the meaning of ' and ',
C is calculated respectively according to above formulaMean valueAnd variance
Wherein, α_{i}It represents to send assemble of symbol { 1,1 }；
D calculates the observer nodes of jth of user in the t times iterative processTo the symbol node x of ith of user_{i} [n] transmits the mean value of messageAnd variance
WhereinRepresent the observer nodes of jth of userWith the symbol node x of ith of user_{i}Between [n] Equivalent channel gain, σ^{2}Represent the variance of white Gaussian noise,
E, based on abovementioned mean valueAnd varianceUsing Gaussian approximation, calculate in the t times iteration In the process, the observer nodes of jth of userTo the symbol node x of ith of user_{i}The message that [n] is transmitted
Demodulation deinterleaves：According toThe symbol of ith of user in the t times iterative process is calculated Number node x_{i}[n] is to the input node of decoderThe message of transmission
Wherein, n=1,2 ..., N', N'=NL, l=1,2 ..., L,
According to above formula, the input message of decoder is further obtained
Decoding：By the input node of the decoderThe message transmitted to decoder is mapped as the shape of loglikelihood ratio Formula, judgement obtain the information bit sequence of corresponding each user
Abovementioned Multiuser Detection step is repeated to decoding procedure, until t=T.
The nonopiate multiple access is sent and joint reception demodulation coding method, in channel coding step, coding Mode is using any one of convolutional code, LDPC code, Turbo code, Turbo product codes.
The nonopiate multiple access is sent and joint reception demodulation coding method, and in modulation step, use is orthogonal The modulation of any one of amplitude modulation (QAM), four phase shift keying signal (QPSK), multisystem digital phase modulation (MPSK) Mode.
The nonopiate multiple access is sent and joint reception demodulation coding method, in interleaving steps, using grouping Any one of interleaver, convolutional deinterleaver and random interleaver.
Method is compared with conventional multiuser interference elimination method with following two notable features in the present invention：
(1) interference performance enhancing is eliminated；
(2) computational complexity reduces；
Description of the drawings
Fig. 1 is the nonopiate access of multiuser of the present invention and transmission flow figure.
Fig. 2 is that multiuser association of the present invention receives demodulation coding flow chart.
Fig. 3 is the simulation curve in the case of Case 1 and Case 2.
Specific embodiment
The present invention is described in further details with reference to the accompanying drawings and examples.
Nonopiate multiple access proposed by the present invention is sent and joint receives demodulation coding system and method, is given below Workflow is easy to understand objects, features and advantages of the present invention.Two big systems are broadly divided into, are connect first, multiuser is nonopiate Enter and send, first, the joint of multiuser receives demodulation coding.
(1) as shown in Figure 1, the nonopiate access of multiuser and transmission system, map equipped with channel coding module, coded identification Module, interleaving block and modulation module (each operation according to the following steps per family)：
Channel coding module：To the information sequence b of kth of user_{k}Carry out channel coding, k=1,2 ..., K, by channel Output sequence c after coding_{k}, L is sequence c after coding_{k}Length；
Coded identification mapping block：The sequence c_{k}In each symbol be each mapped to the feature that length is N Sequence p_{k}, N is natural number more than or equal to 1, p_{k}={ z_{1},z_{2},...,z_{N}, z_{i}∈ { 1, 1 }, i=1,2 ..., N, i are characterized The serial number of parameter z, N are characterized the number of parameter, and the mapping ruler of symbol is according to 1 → p_{k}, 0 →p_{k}, map postorder and be classified as r_{k}；
Interleaving block：The sequence r of input_{k}It is interleaved, obtains sequence v_{k}；
Modulation module：The sequence v of input_{k}It is modulated, obtains sequence u_{k}, it is sent to receiving terminal；
(2) joint of multiple user signals receives demodulation coding system, is equipped with：Multiuser detection module, demodulation reconciliation Interleaving block and decoding module：
First by the reception sequences y of kth of user_{k}[n] is multiplied by the characteristic sequence p of each user symbolbysymbol_{k}, obtain kth The observer nodes of userWherein K be user number, k=1,2 ..., K, n be each symbol the time of reception, n=1, 2 ..., N', N'=NL, L be coding after sequence c_{k}Length, N is characterized sequence p_{k}Length, l=1,2 ..., L, willAs the input of multiuser detection module, into iterative process；
Multiuser detection module is detected according to following steps：
A is initialized, setting：T is iterations, and t is current iteration number, t=1,2 ..., T, i=1,2 ..., K, j =1,2 ..., K, K be user number, when initial, by ith of user moment n symbol node x_{i}[n] is to jth of user Observer nodesThe message of transmissionIn x_{i}It is during [n]=1In x_{i}It is during [n]= 1
B is calculated in the t times iterative process by the symbol node x of ith of user_{i}[n] is to the observer nodes of jth of userThe message of transmission
C is calculated respectively according to above formulaMean valueAnd variance
D calculates the observer nodes of jth of user in the t times iterative processTo the symbol node x of ith of user_{i} [n] transmits the mean value of messageAnd variance
E, based on abovementioned mean valueAnd varianceUsing Gaussian approximation, calculate in the t times iteration In the process, the observer nodes of jth of userTo the symbol node x of ith of user_{i}The message that [n] is transmitted
Demodulation deinterleaving block：According toIth of user in the t times iterative process is calculated Symbol node x_{i}[n] is to the input node of decoderThe message of transmissionAnd the input of decoder Message；
Decoding module：By the input node of the decoderThe message transmitted to decoder is mapped as loglikelihood ratio Form, judgement obtains the information bit sequence of corresponding each user
Abovementioned Multiuser Detection module is repeated between decoding module the step of until t=T.
The specific embodiment of the present invention
Nonopiate multiple access proposed by the present invention is sent and joint receives demodulation coding system and method, with more than one For user's cdma spread spectrum communication system, spreading ratio N=16, system user number is K=6, it is assumed that using the LDPC of 1/2 code check Coding, code length 1024, using perfect power control, BPSK modulation, random interleaving, channel is awgn channel.It gives below Go out workflow, be easy to understand objects, features and advantages of the present invention.
(1) to the information bit sequence b of each user_{k}Carry out LDPC codings, the sequence c after being encoded_{k}；
(2) by the sequence c after coding_{k}Divide the sequence for being mapped as that length is N (N is the natural number more than or equal to 1)
p_{k}={ z_{1},z_{2},...,z_{N}},(z_{i}∈ { 1, 1 }, i=1,2 ..., N), the sequence r after being spread_{k}, mapping ruler It is as follows：1→p_{k}, 0 →p_{k}, complete spread spectrum；
(3) to the sequence r after spread spectrum_{k}Random interleaving processing is carried out, obtains sequence v_{k}；
(4) to sequence v_{k}Launch after carrying out BPSK modulation；
(5) radio frequency unit of terminal receives signal, realizes down coversion and analog to digital conversion, generates digital baseband signal；
(6) the sequence p that sequences y [n] is multiplied by each user symbolbysymbol will be received_{k}, obtain the K roads sequence of corresponding K userWherein k=1,2 ..., K, n=1,2 ..., NL, L be sequence c after coding_{k}Length.
(7) by the observer nodes of K userMultiuser Detection node is substituted into, according toValue, with reference to confidence Algorithm and centrallimit theorem calculate message described in the t times iterative processAnd
(8) basisValue, calculate x_{i}(n) toThe message of transmission
(9) basisIt calculatesThe message transmitted to decoder
It (10) in a decoder, will be abovementionedThe message transmitted to decoder is mapped as the form of loglikelihood ratio:Based on loglikelihood ratio, the information bit sequence of corresponding each user is obtained
(11) (7)(11) are repeated the above process, until meeting iterations.
Computer Simulation test is carried out to above system, has obtained following result：
Following two groups of simulation parameters are set, as shown in table 1.
Table 1
Fig. 3 illustrates the simulation curve in the case of Case 1 and 2 two kinds of Case, is calculated with the iteration MMSE in the case of two kinds Method is compared, and the Joint iteration algorithm under identical iterations can effectively improve the performance of system, and with iterations Increase, the performance of Joint iteration algorithm be more nearly single user it is noiseless when performance.
The effect of the present invention is the propagation on factor graph that is formed by using external information in Multiuser Detection node and more New the characteristics of making external information relatively reliable, the relatively low influence of ambient noise and interference to signal message, obtained compared with Low error code result and more reliable laser propagation effect, at the same this algorithm can realize multiuser interference eliminate and decoding combine into Row, is conducive to the realization of parallel organization.Therefore, multiuser interference is eliminated, this method is substantially better than other methods.
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