CN109104269A - A kind of time-division half-duplex satellite communication system - Google Patents
A kind of time-division half-duplex satellite communication system Download PDFInfo
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- CN109104269A CN109104269A CN201810656061.1A CN201810656061A CN109104269A CN 109104269 A CN109104269 A CN 109104269A CN 201810656061 A CN201810656061 A CN 201810656061A CN 109104269 A CN109104269 A CN 109104269A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/14—Two-way operation using the same type of signal, i.e. duplex
- H04L5/16—Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18515—Transmission equipment in satellites or space-based relays
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18578—Satellite systems for providing broadband data service to individual earth stations
- H04B7/1858—Arrangements for data transmission on the physical system, i.e. for data bit transmission between network components
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18578—Satellite systems for providing broadband data service to individual earth stations
- H04B7/18586—Arrangements for data transporting, e.g. for an end to end data transport or check
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0057—Block codes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0059—Convolutional codes
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0064—Concatenated codes
Abstract
The present invention relates to satellite communication field, solves the technical problem of satellite communication error floor in the prior art and code construction complexity.The technical scheme of the present invention is realized as follows: a kind of time-division half-duplex satellite communication system, for sending the communication between satellite S, repeater satellite R and stay of two nights satellite D, comprising: the adaptive relay forwarding agreement based on PLG code.A kind of time-division half-duplex satellite communication system disclosed in this invention, and PLG code system and a kind of adaptive trunk protocol (ARP) for this system are proposed come the information processing of satellite each in control system, meet the strict demand of satellite communication, implementation complexity is low, approach shannon limit performance, inerrancy leveling.
Description
Technical field
The present invention relates to satellite communication fields, particularly relate to a kind of time-division half-duplex satellite communication system.
Background technique
In satellite communication system, how to find strong error control coding to approach Shannon capacity limit is the past
The target that decades coding scholar pursues always.Up to the present, it has been widely applied there are many error-Control Coding Schemes
In satellite communication system, for example, BCH (Bose, Chaudhari and Hocquenghem) code, RS (Reed-Solomon)
Code, convolutional code and loe-density parity-check code (low density parity check, LDPC).
LDPC code is a kind of random coded, has proven to be a kind of most promising nearly shannon limit channel coding schemes.
But when conventional LDPC code is applied in actual communication environment, encoding and decoding complexity is the problem of cannot ignoring, because
Usually they need the encoder complexity of quadratic power.Low-density generated matrix (Low density generator matrix,
LDGM) code possesses lower uniform enconding complexity as a kind of special LDPC code, while can use the BP of low complex degree
Algorithm decoding.In spite of these advantages, but all the time LDGM code be considered be not a kind of special strength coding, reason
The check matrix for being LDGM includes the too many column spent for 1, and which results in unacceptable high error floor, this phenomenons
It will not be changed with the increase of code length.
Recently, Arikan proposes a newest concept, and referred to as channel-polarization constructs the letter of entitled polarization code a kind of
Road encoding scheme, the program can achieve symmetrical binary discrete memoryless channel(DMC) (binary-input discrete
Memoryless channels, B-DMC) channel capacity.Compared with LDPC code, polarization code has not available for LDPC code
Advantage such as has low encoding and decoding complexity simultaneously, is not influenced by error floor.But compared with progressive theoretical performance, have
The polarization code of limit code length does not show performance outstanding but in practical application.Therefore a large amount of research work is conceived to
The decoder for improving polarization code, improves its BER performance.
Polarization code is carried out cascade idea as outer code and LDPC code to study in the prior art, program sheet
Invention is known as polar-LDPC (PLP) code.PLP code is applied in optical-fiber network, can be obtained than some traditional schemes compared to more
Good performance.But the building method of PLP code is obtained by the method for emulation experiment, this is the method for experience and unreasonably
The method of opinion.In addition the channel that the polarization code in PLP code is observed is assumed to be a virtual binary eliminated channel
(binary erasure channel, BEC), the capacity of the BEC channel is configured to consistent with polarization code code rate, and polarizes
The code Design of code is namely based on this channel, and realized using didactic building method in the prior art.Therefore, outside
The design of polarization code is not optimal design.
The special case of single relay system is considered for the research of relay satellite system.Due to channel capacity theory
Reachable, extensive research has been obtained in the relay system based on polarization code, these applications are based on different coordination strategies, needle
Various channel conditions are designed with polarization code scheme, such as decoding forwarding decode and forward (DF) and compression forwarding
Compress and forward (CF), still, most research work are the theory analysis for being conceived to progressive performance,
The long BER performance of middle short code obtained is generally all very poor.It is well known that LDPC code approaches the performance of shannon limit due to having,
It therefore is also a kind of one of the powerful channel coding schemes of relay system, but the complexity of its code construction is still very high, it is former
Because being the combined optimization design for needing to encode, in addition when BER drops to 10-7-10-8When, start error floor occur.Therefore, if
Actual channel coding schemes are counted, to meet the strict requirements of satellite communication, it is sex-limited to approach Shannon for such as low implementation complexity
Can, inerrancy leveling etc. is still a challenging problem.
Urgently there is a kind of Novel Communication mode that can be solved the above problems.
Summary of the invention
A kind of time-division half-duplex satellite communication system disclosed by the invention, solves satellite communication mistake in the prior art
The technical problem of leveling and code construction complexity.
The technical scheme of the present invention is realized as follows: a kind of time-division half-duplex satellite communication system, for sending satellite
S, the communication between repeater satellite R and stay of two nights satellite D, comprising: the adaptive relay forwarding agreement based on PLG code.
The relay forwarding agreement includes:
(A), it sends the processing of satellite S nodal information: defining between the channel and S and R in satellite communication system between S and D
Channel is expressed as WSDAnd WSR；Enable ASDAnd ASRIt is polarization code according to channel WSDAnd WSRInformation bit set generated, wherein WSD
It is WSRDegenerate channel, then haveBy channel WSRAll bit index set [N1]@{1,K,N1It is divided into three
A independent subset:
ASR\ASDExpression is channel WSRInformation bit set and WSDFixed bit set；
ASDIt indicates while being channel WSRAnd WSDInformation bit set；
F=[N1]\ASRIt is simultaneously WSRAnd WSDFixed bit set；
It enablesFor the information vector of S, it is N that wherein u, which is length,1Information source input, m be divided to for two it is independent it is sub to
Amount, is expressed asWith
In time slot I, sends satellite S and send all information bit m and fixed bit 0, a length of N of generated code1Polarization code
Code wordBroadcast transmission is to repeater satellite R and the stay of two nights satellite D, channel WSRCode rate be
For channel WSD, transmit m2Code rate be
In time slot II, sends satellite S and cooperate with repeater satellite R, send m1Partial information bit transfer to D, S node
PLG code the encoder of polarization code and the encoder of LDGM be sequentially generated code length be N2Code wordThe code word is by code length
For N3Polarization code code word v and length are (N2-N3) the check bit p of LDGM code formed；
The code rate of PLG code is
(B), repeater satellite R nodal information is handled: sending stay of two nights satellite D in time slot II, repeater satellite R can be reliable extensive
The useful help information of multiple m；Receiving yRAfterwards, information of the R based on fixed bit 0 can decode m；
It is no that the relaying detector of ARP protocol only detects whether that relaying needs to retransmit；
(C), stay of two nights satellite D nodal information is handled: in the coda of entire transmission time slot, when stay of two nights satellite D has received two
The code length of gap is respectively N1And N2Code word, and they are decoded in order；Stay of two nights satellite D uses PLG code decoder to reception first
The signal arrivedDecoding obtains N2Coded-bit；
According toUsing polarization code decoder, by estimated obtained useful informationAnd check bitAs priori
Information recovering goes outBy merging decoded information, reconstruct
(B) according to ARP protocol in, if detection makes mistake, the estimated value of m is due to being just being rejected for inaccuracy, R guarantor
Hold silence；If repeater satellite R decoding is correct, repeater satellite R need to only select the part estimated value of m, be expressed asIt is logical
Crossing polarization code coder willIt is encoded intoRepeater satellite R passes through LDGM encoder pairIt recompiles, a length of N of generated code2-N3
LDGM code check bit
(C) stay of two nights satellite D can be received in decoding about m in1Prior information, the channel that time slot I is received
It directly decodes.
The PLG code includes polarization code and LDGM code:
The polarization code, LDGM code serially concatenated, the PLG code by outer code of polarization code and by Internal Code of LDGM code；
Or the polarization code, LDGM code parallel cascade；Including one group using polarization code as outer code, using LDGM code as Internal Code
PLG code and one group of PLG code using polarization code as Internal Code, by outer code of LDGM code.
The coding method of the PLG code includes:
A, information bit u=[u1,...,uK] by (N1, K) and polarization code coding；
B, the code word exportedBy (N, N1) LDGM code coding after, output codonsWhereinIt is the check bit of LDGM code；Entirely the code rate of concatenated code is
K/N；
C, after BPSK modulation (binary-phase shift-keying, BPSK), signal is believed by AWGN
Road (additive Gaussian noise, AWGN), bilateral power spectral density are σ2=N0/2；
D, in receiving end, reception signal is y=[y1,...,yN], it is decoded in LDGM decoder after demodulation, then pole
Change code decoder using the LLR Soft Inform ation (log likelihood ratios, LLRs) of LDGM decoder output as initial
Change information, the input processing as BP decoder.
The coding/decoding method of the PLG code includes:
A, initialize: in receiving end, the LLR value calculating for receiving signal y is as follows
Then the value can be used for initializing
L(qij)=L (vi)=L (ci),1≤i≤N1
L(rji)=L (sj)=L (ci),N1+1≤i≤N
Wherein L (qij) and L (rji) indicate bit node viWith check-node sjInitialization information；
B, LDGM code decodes: from sjTo viMessage transmission updated value L (rji) calculate it is as follows
Wherein, tanh (x/2)=(ex-1)/(ex+ 1), VjIndicate viConnect sjSet；Correspondingly, from viTo sjDisappear
Breath transmitting updated value L (qij) be
Wherein, SiFor sj connection viSet.Then, whole LLR information of i-th of systematic bits node are updated, therefore can
?
C, polarization code decodes: the output Soft Inform ation of LDGM decoder can be used as the input of polarization code decoder as just
Beginningization information
Wherein, 1≤l≤n1+ 1,1≤i≤N1.In addition, the information R issued from information source1,iIt is initialized as
The equilibrium relationships that message transmission updates can calculate as follows:
Wherein,And for any two real number x and y, there is f (x, y)=ln ((1+xy)/(x+y))；Function f
The calculation method of (x, y) can similar to f (x, y) ≈ sign (x) sign (y) min (| x |, | y |)；
D, final decision: the estimated value of the message of transmission is finally determined by decision rule, as follows
Iteration stopping criterion: ifIt sets up, then decoder is exportedIt is exactly the value that is effectively estimated of u, then stops
Only subsequent iteration；Otherwise, return to decoding concatenated code device and execute next iteration, until the number of iterations reach it is set most
Until big value.
The polarization code and LDGM code use BP coding/decoding method；The BP coding/decoding method includes the stopping of analysis factor figure
Distance and minimum stop distance；The stop distance of polarization code and LDGM code that the code length is N is
Wise error probability analysis is carried out to polarization code and LDGM code by Gaussian approximation method, the Gaussian approximation method is specific
It is:
(a), PLG encoding scheme is set, Average Error Probabilities are
Wherein,For the error probability of i-th of bit channel that polarizes, A is that the information bit of polarization code indexes set；
(b), assume send length be N full 0 code word, then byThe calculated y of institute is equal
It is Gaussian random variable；According to GA, the BP decoder of LDGM code is in the output mean value of i-th of variable node of the t times iteration
Wherein, μ0,iIt is the initial mean value for observing obtained i-th of the channel massage of y,Be in the t-1 times iteration,
The mean value of input message from j-th of check-node, dvIt is the degree of variable node, mean valueIt calculates as follows
Wherein, dcIt is the degree of check-node, and for μ >=0, function phi (μ) is defined as follows
(c), after the completion of LDGM decoder iteration, final mean value obtainedIt is passed to the cascade polarization code of institute
Initialization operation is realized in decoder, wherein tldgmIt is the maximum number of iterations of LDGM code decoder, updates each variable node
LLR value, it is as follows
Wherein,WithIt is the t times iteration, the left and right LLR value of variable node respectively；
For the polarization code based on GA method, by formula
The calculated value of institute is also considered as Gaussian random variable, and relationship isWithWherein D [] and E [] is variance and mean value respectively；Ensuring only need to be by tracking mean value
With, so that complexity be greatly reduced；Then have
In recursive calculation finally, enabling
So the error probability of each polarization bit channel is represented by
Wherein,tpolarIt is the maximum number of iterations of polarization code decoder；
(d), final Average Error Probabilities can be by formulaIt calculates.
Time-division half-duplex satellite communication system in disclosed in this invention one, and propose the PLG code system for this system
System and a kind of adaptive trunk protocol (ARP) carry out the information processing of each satellite in control system, meet the tight of satellite communication
Lattice requirement, implementation complexity is low, approaches shannon limit performance, inerrancy leveling.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, below will to embodiment or
Attached drawing needed to be used in the description of the prior art is briefly described, it should be apparent that, the accompanying drawings in the following description is only
Some embodiments of the present invention, for those of ordinary skill in the art, without any creative labor,
It is also possible to obtain other drawings based on these drawings.
Fig. 1: Polar-LDGM code system block diagram；
Fig. 2: the performance comparison figure of different encoding schemes；
Fig. 3: the Polar-LDGM code performance gain contrast figure of different code length；
Fig. 4: time-division half-duplex satellite communication system block diagram；
Code word design method at Fig. 5: time slot I and time slot II, information source satellite S；
Fig. 6: the information processing scheme of repeater satellite；
Fig. 7: the information processing scheme of stay of two nights satellite decoder；
Fig. 8: signal-to-noise ratio is (Eb/N0)SR=8dB and (Eb/N0)RDWhen=8dB, the BER of difference relaying coded system
It can comparison diagram.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts it is all its
His embodiment, shall fall within the protection scope of the present invention.
As shown in figure four time-divisions half-duplex satellite communication system block diagram, a kind of time-division half-duplex satellite disclosed by the invention
Communication system, for sending the communication between satellite S, repeater satellite R and stay of two nights satellite D, comprising: based on the adaptive of PLG code
Relay forwarding agreement.The effect of repeater satellite R is to help to forward the message for sending satellite S using the broadcast characteristic of wireless channel
To stay of two nights satellite D.Assuming that all satellites all configure an antenna, it is only capable of receiving or sends message, and when repeater satellite R is
Divide half-duplex operating mode.Specifically, M is encoded in time slot I, S, then broadcasts code wordIn the received message of R and D
It is expressed as YRWithIn time slot II, R is according to YRThe estimated value decodedGenerate code word XRAfterwards, it is forwarded to D.With
This simultaneously, S also sends a code wordCorrespondingly, signal is merged at D isFinally, the estimated value of information source messageIt can be with
According toDecoding.
The relay forwarding agreement includes:
(A), it sends the processing of satellite S nodal information: defining between the channel and S and R in satellite communication system between S and D
Channel is expressed as WSDAnd WSR；Enable ASDAnd ASRIt is polarization code according to channel WSDAnd WSRInformation bit set generated, wherein WSD
It is WSRDegenerate channel, then haveBy channel WSRAll bit index set [N1]@{1,K,N1It is divided into three
A independent subset:
ASR\ASDExpression is channel WSRInformation bit set and WSDFixed bit set；
ASDIt indicates while being channel WSRAnd WSDInformation bit set；
F=[N1]\ASRIt is simultaneously WSRAnd WSDFixed bit set；
It enablesFor the information vector of S, it is N that wherein u, which is length,1Information source input, m be divided to for two it is independent it is sub to
Amount, is expressed asWith
Shown in code word design method at such as figure five time slot I and time slot II, information source satellite S, in time slot I, satellite S is sent
Send all information bit m and fixed bit 0, a length of N of generated code1Polarization code code wordBroadcast transmission is defended to relaying
Star R and the stay of two nights satellite D, channel WSRCode rate be
For channel WSD, transmit m2Code rate be
In time slot II, sends satellite S and cooperate with repeater satellite R, send m1Partial information bit transfer to D, S node
PLG code the encoder of polarization code and the encoder of LDGM be sequentially generated code length be N2Code wordThe code word is by code length
For N3Polarization code code word v and length are (N2-N3) the check bit p of LDGM code formed；
The code rate of PLG code is
As shown in the information processing scheme of six repeater satellite of figure, the processing of (B), repeater satellite R nodal information: in time slot II,
Repeater satellite R sends the useful help information that stay of two nights satellite D is capable of Trusted recovery m；Receiving yRAfterwards, R is based on fixed bit 0
Information, m can be decoded；According to ARP protocol, if detection makes mistake, the estimated value of m is due to being just being given up for inaccuracy
It abandons, R keeps silent；If repeater satellite R decoding is correct, repeater satellite R need to only select the part estimated value of m, be expressed asIt will by polarization code coderIt is encoded intoRepeater satellite R passes through LDGM encoder pairIt recompiles, generates code length
For N2-N3LDGM code check bit
It is no that the relaying detector of ARP protocol only detects whether that relaying needs to retransmit；
As shown in the information processing scheme of seven stay of two nights satellite decoder of figure, the processing of (C), stay of two nights satellite D nodal information:
The coda of entire transmission time slot, the code length that stay of two nights satellite D has received two time slots is respectively N1And N2Code word, and in order to him
Decode；Stay of two nights satellite D is first with PLG code decoder to the signal receivedDecoding obtains N2Coded-bit；
According toUsing polarization code decoder, by estimated obtained useful informationAnd check bitAs priori
Information recovering goes outBy merging decoded information, reconstruct
Stay of two nights satellite D can be received in decoding about m1Prior information, the channel that time slot I is receivedDirectly solve
Code.
The PLG code includes polarization code and LDGM code:
The polarization code, LDGM code serially concatenated, the PLG code by outer code of polarization code and by Internal Code of LDGM code；
Or the polarization code, LDGM code parallel cascade；Including one group using polarization code as outer code, using LDGM code as Internal Code
PLG code and one group of PLG code using polarization code as Internal Code, by outer code of LDGM code.
The coding method of the PLG code includes:
A, information bit u=[u1,...,uK] by (N1, K) and polarization code coding；
B, the code word exportedBy (N, N1) LDGM code coding after, output codonsWhereinIt is the check bit of LDGM code；Entirely the code rate of concatenated code is
K/N；
C, after BPSK modulation (binary-phase shift-keying, BPSK), signal is believed by AWGN
Road (additive Gaussian noise, AWGN), bilateral power spectral density are σ2=N0/2；
D, in receiving end, reception signal is y=[y1,...,yN], it is decoded in LDGM decoder after demodulation, then pole
Change code decoder using the LLR Soft Inform ation (log likelihood ratios, LLRs) of LDGM decoder output as initial
Change information, the input processing as BP decoder.
The coding/decoding method of the PLG code includes:
A, initialize: in receiving end, the LLR value calculating for receiving signal y is as follows
Then the value can be used for initializing
L(qij)=L (vi)=L (ci),1≤i≤N1
L(rji)=L (sj)=L (ci),N1+1≤i≤N
Wherein L (qij) and L (rji) indicate bit node viWith check-node sjInitialization information；
B, LDGM code decodes: from sjTo viMessage transmission updated value L (rji) calculate it is as follows
Wherein, tanh (x/2)=(ex-1)/(ex+ 1), VjIndicate viConnect sjSet；Correspondingly, from viTo sjDisappear
Breath transmitting updated value L (qij) be
Wherein, SiFor sjConnect viSet.Then, whole LLR information of i-th of systematic bits node are updated, therefore can
?
C, polarization code decodes: the output Soft Inform ation of LDGM decoder can be used as the input of polarization code decoder as just
Beginningization information
Wherein, 1≤l≤n1+ 1,1≤i≤N1.In addition, the information R issued from information source1,iIt is initialized as
The equilibrium relationships that message transmission updates can calculate as follows:
Wherein,And for any two real number x and y, there is f (x, y)=ln ((1+xy)/(x+y))；Function f
The calculation method of (x, y) can similar to f (x, y) ≈ sign (x) sign (y) min (| x |, | y |)；
D, final decision: the estimated value of the message of transmission is finally determined by decision rule, as follows
Iteration stopping criterion: ifIt sets up, then decoder is exportedIt is exactly the value that is effectively estimated of u, then stops
Only subsequent iteration；Otherwise, return to decoding concatenated code device and execute next iteration, until the number of iterations reach it is set most
Until big value.
The polarization code and LDGM code use BP coding/decoding method；The BP coding/decoding method includes the stopping of analysis factor figure
Distance and minimum stop distance；The stop distance of polarization code and LDGM code that the code length is N is
Wise error probability analysis is carried out to polarization code and LDGM code by Gaussian approximation method, the Gaussian approximation method is specific
It is:
(a), PLG encoding scheme is set, Average Error Probabilities are
Wherein,For the error probability of i-th of bit channel that polarizes, A is that the information bit of polarization code indexes set；
(b), assume send length be N full 0 code word, then byThe calculated y of institute is equal
It is Gaussian random variable；According to GA, the BP decoder of LDGM code is in the output mean value of i-th of variable node of the t times iteration
Wherein, μ0,iIt is the initial mean value for observing obtained i-th of the channel massage of y,Be in the t-1 times iteration,
The mean value of input message from j-th of check-node, dvIt is the degree of variable node, mean valueIt calculates as follows
Wherein, dcIt is the degree of check-node, and for μ >=0, function phi (μ) is defined as follows
(c), after the completion of LDGM decoder iteration, final mean value obtainedIt is passed to the cascade polarization code of institute
Initialization operation is realized in decoder, wherein tldgmIt is the maximum number of iterations of LDGM code decoder, updates each variable node
LLR value, it is as follows
Wherein,WithIt is the t times iteration, the left and right LLR value of variable node respectively；
For the polarization code based on GA method, by formula
The calculated value of institute is also considered as gaussian random
Variable, relationship areWithWherein D [] and E [] is variance and mean value respectively；
Ensuring only need to be by tracking mean valueWith, so that complexity be greatly reduced；Then have
In recursive calculation finally, enabling
So the error probability of each polarization bit channel is represented by
Wherein,tpolarIt is the maximum number of iterations of polarization code decoder；
(d), final Average Error Probabilities can be by formulaIt calculates, to complete to prove.
Simulation result analyzes the BER performance of the satellite communication system based on PLG code proposed. (Eb/N0)SR,(Eb/
N0)RD(Eb/N0)SDRespectively indicate S to R, the SNR of R to D, S to D link.The simulation parameter used in us subsequent in this way is said
It is bright as shown in the table:
Simulation parameter
Such as eight signal-to-noise ratio of figure is (Eb/N0)SR=8dB and (Eb/N0)RDWhen=8dB, the BER of difference relaying coded system
Shown in performance comparison figure, the scheme based on PLG code is compared, with the BER based on polarization code and LDPC code relay system scheme
Can, simulation result shows that PLG code scheme is substantially better than and polarization code scheme is used alone.In addition, the error correcting capability of PLG code can be with
Reach low-down BER (i.e. 10-10, or lower), also without discovery error floor, meet satellite communication system minimum BER
Demand.For the LDPC code scheme in figure, it is virtually impossible to reach so low BER, because there is error floor.Pass through
Using ARP protocol also and conventional without using the scheme of detector to compare.The result shows that can be obtained using ARP
Better BER performance, it was confirmed that the conclusion of theorem 3, this is because conventional method does not use detector, R is unable to ensure pair
Help information reliable decoding.And the information forwarded can further deteriorate the transmission of R to D link, this will affect the stay of two nights and disappears to information source
The decoding of breath.However, when having used ARP protocol, because R can more reliably transmit help information, therefore when RD link is preferable
When, D is more able to the information reliable decoding received in time slot I.
New PLG code scheme, the program have lower encoding and decoding complexity.By cascade, the polarization code of high code rate can
With the error floor problem for LDGM code of eliminating the effects of the act, while ensuring preferable constringency performance.It is proposed by the present invention to be based on the side GA
The PLG code structural scheme of method is capable of the error probability of theoretically analytical plan.Emulation, which is compared, shows that PLG code is a kind of tool
Promising coding techniques, the reason is that having the performance and inerrancy leveling for approaching channel capacity limit.In addition, present invention institute is public
A kind of high speed satellite communication system based on PLG code and corresponding APR agreement are opened, through selectively forwarding information from R to D
Satellite.In ARP agreement, in the information process of each satellite node.By proving, the scheme proposed, based on solution
The judgement of code error detector, can improve the error probability of system.Finally, the present invention and existing modern coding method carry out
Compare, shows that PLG code scheme can be used as the alternative solution for having much prospect of next-generation satellite communication system.
Time-division half-duplex satellite communication system in disclosed in this invention one, and propose the PLG code system for this system
System and a kind of adaptive trunk protocol (ARP) carry out the information processing of each satellite in control system, meet the tight of satellite communication
Lattice requirement, implementation complexity is low, approaches shannon limit performance, inerrancy leveling.
Certainly, without deviating from the spirit and substance of the present invention, those skilled in the art should can be with
Various corresponding changes and modifications are made according to the present invention, but these corresponding changes and modifications all should belong to appended by the present invention
Scope of protection of the claims.
Claims (9)
1. a kind of time-division half-duplex satellite communication system, logical between satellite S, repeater satellite R and stay of two nights satellite D for sending
Letter characterized by comprising the adaptive relay forwarding agreement based on PLG code.
2. a kind of time-division half-duplex satellite communication system according to claim 1, it is characterised in that: the relay forwarding association
View includes:
(A), it sends the processing of satellite S nodal information: defining the channel between the channel and S and R in satellite communication system between S and D
It is expressed as WSDAnd WSR；Enable ASDAnd ASRIt is polarization code according to channel WSDAnd WSRInformation bit set generated, wherein WSDIt is WSR
Degenerate channel, then haveBy channel WSRAll bit index set [N1]@{1,K,N1It is divided into three independences
Subset:
ASR\ASDExpression is channel WSRInformation bit set and WSDFixed bit set；
ASDIt indicates while being channel WSRAnd WSDInformation bit set；
F=[N1]\ASRIt is simultaneously WSRAnd WSDFixed bit set；
It enablesFor the information vector of S, it is N that wherein u, which is length,1Information source input, m be divided to for two independent subvectors, divides
It is not expressed asWith
In time slot I, sends satellite S and send all information bit m and fixed bit 0, a length of N of generated code1Polarization code code wordBroadcast transmission is to repeater satellite R and the stay of two nights satellite D, channel WSRCode rate be
For channel WSD, transmit m2Code rate be
In time slot II, sends satellite S and cooperate with repeater satellite R, send m1Partial information bit transfer to D, the PLG code of S node
The encoder of polarization code and the encoder of LDGM be sequentially generated code length be N2Code wordThe code word is N by code length3Pole
Change code code word v and length is (N2-N3) the check bit p of LDGM code formed；
The code rate of PLG code is
(B), repeater satellite R nodal information is handled: being sent stay of two nights satellite D in time slot II, repeater satellite R and is capable of Trusted recovery m's
Useful help information；Receiving yRAfterwards, information of the R based on fixed bit 0 can decode m；
It is no that the relaying detector of ARP protocol only detects whether that relaying needs to retransmit；
(C), stay of two nights satellite D nodal information is handled: in the coda of entire transmission time slot, stay of two nights satellite D has received two time slots
Code length is respectively N1And N2Code word, and they are decoded in order；Stay of two nights satellite D is first with PLG code decoder to the letter received
NumberDecoding obtains N2Coded-bit；
According toUsing polarization code decoder, by estimated obtained useful informationAnd check bitAs prior information
It recoversBy merging decoded information, reconstruct
3. a kind of time-division half-duplex satellite communication system according to claim 2, it is characterised in that: assisted in (B) according to ARP
View, if detection makes mistake, the estimated value of m is due to being just being rejected for inaccuracy, R holding silence；If repeater satellite R is decoded
If correct, repeater satellite R need to only select the part estimated value of m, be expressed asIt will by polarization code coderIt is encoded intoRepeater satellite R passes through LDGM encoder pairIt recompiles, a length of N of generated code2-N3LDGM code check bit
4. a kind of time-division half-duplex satellite communication system according to claim 2, it is characterised in that: stay of two nights satellite D in (C)
It can receive in decoding about m1Prior information, the channel that time slot I is receivedIt directly decodes.
5. according to claim 2 --- a kind of time-division half-duplex satellite communication system, feature described in any one of 4 exist
In: the PLG code includes polarization code and LDGM code:
The polarization code, LDGM code serially concatenated, the PLG code by outer code of polarization code and by Internal Code of LDGM code；
Or the polarization code, LDGM code parallel cascade；PLG code including one group using polarization code as outer code, by Internal Code of LDGM code
With one group of PLG code using polarization code as Internal Code, by outer code of LDGM code.
6. a kind of time-division half-duplex satellite communication system according to claim 5, it is characterised in that: the volume of the PLG code
Code method include:
A, information bit u=[u1,...,uK] by (N1, K) and polarization code coding；
B, the code word exportedBy (N, N1) LDGM code coding after, output codonsWhereinIt is the check bit of LDGM code；The code rate of entire concatenated code is K/
N；
C, after BPSK modulation (binary-phase shift-keying, BPSK), signal passes through awgn channel
(additive Gaussian noise, AWGN), bilateral power spectral density are σ2=N0/2；
D, in receiving end, reception signal is y=[y1,...,yN], it is decoded in LDGM decoder after demodulation, then polarization code
Decoder is using the LLR Soft Inform ation (log likelihood ratios, LLRs) of LDGM decoder output as initialization letter
Breath, the input processing as BP decoder.
7. a kind of time-division half-duplex satellite communication system according to claim 6, it is characterised in that: the solution of the PLG code
Code method include:
A, initialize: in receiving end, the LLR value calculating for receiving signal y is as follows
Then the value can be used for initializing
L(qij)=L (vi)=L (ci),1≤i≤N1
L(rji)=L (sj)=L (ci),N1+1≤i≤N
Wherein L (qij) and L (rji) indicate bit node viWith check-node sjInitialization information；
B, LDGM code decodes: from sjTo viMessage transmission updated value L (rji) calculate it is as follows
Wherein, tanh (x/2)=(ex-1)/(ex+ 1), VjIndicate viConnect sjSet；Correspondingly, from viTo sjMessage transmission
Updated value L (qij) be
Wherein, SiFor sjConnect viSet.Then, whole LLR information of i-th of systematic bits node are updated, therefore can be obtained
C, polarization code decodes: the output Soft Inform ation of LDGM decoder can be used as the input of polarization code decoder as initialization letter
Breath
Wherein, 1≤l≤n1+ 1,1≤i≤N1.In addition, the information R issued from information source1,iIt is initialized as
The equilibrium relationships that message transmission updates can calculate as follows:
Wherein,And for any two real number x and y, there is f (x, y)=ln ((1+xy)/(x+y))；Function f (x, y)
Calculation method can similar to f (x, y) ≈ sign (x) sign (y) min (| x |, | y |)；
D, final decision: the estimated value of the message of transmission is finally determined by decision rule, as follows
Iteration stopping criterion: ifIt sets up, then decoder is exportedIt is exactly the value that is effectively estimated of u, then stops subsequent
Iteration；Otherwise, it returns to decoding concatenated code device and executes next iteration, be until the number of iterations reaches set maximum value
Only.
8. a kind of time-division half-duplex satellite communication system according to claim 6 or 7, it is characterised in that: the polarization code
BP coding/decoding method is used with LDGM code；The BP coding/decoding method includes the stop distance and minimum stop distance of analysis factor figure；
The stop distance of polarization code and LDGM code that the code length is N is
9. a kind of time-division half-duplex satellite communication system according to claim 6 or 7, it is characterised in that: forced by Gauss
Nearly method to polarization code and LDGM code progress wise error probability analysis, the Gaussian approximation method particularly:
(a), PLG encoding scheme is set, Average Error Probabilities are
Wherein,For the error probability of i-th of bit channel that polarizes, A is that the information bit of polarization code indexes set；
(b), assume send length be N full 0 code word, then byThe calculated y of institute is high
This stochastic variable；According to GA, the BP decoder of LDGM code is in the output mean value of i-th of variable node of the t times iteration
Wherein, μ0,iIt is the initial mean value for observing obtained i-th of the channel massage of y,It is in the t-1 times iteration, from the
The mean value of the input message of j check-node, dvIt is the degree of variable node, mean valueIt calculates as follows
Wherein, dcIt is the degree of check-node, and for μ >=0, function phi (μ) is defined as follows
(c), after the completion of LDGM decoder iteration, final mean value obtainedIt is passed to the cascade polarization code decoder of institute
Middle realization initialization operation, wherein tldgmIt is the maximum number of iterations of LDGM code decoder, updates the LLR of each variable node
Value is as follows
Wherein,WithIt is the t times iteration, the left and right LLR value of variable node respectively；
For the polarization code based on GA method, by formula
The calculated value of institute is also considered as gaussian random change
Amount, relationship areWithWherein D [] and E [] is variance and mean value respectively；Ensure
Tracking mean value need to only be passed throughWith, so that complexity be greatly reduced；Then have
In recursive calculation finally, enabling
So the error probability of each polarization bit channel is represented by
Wherein,tpolarIt is the maximum number of iterations of polarization code decoder；
(d), final Average Error Probabilities can be by formulaIt calculates, to complete to prove.
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