CN102255697A - Distributed physical layer network coding modulation method for multiple access channel in wireless network - Google Patents

Distributed physical layer network coding modulation method for multiple access channel in wireless network Download PDF

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CN102255697A
CN102255697A CN2011102354223A CN201110235422A CN102255697A CN 102255697 A CN102255697 A CN 102255697A CN 2011102354223 A CN2011102354223 A CN 2011102354223A CN 201110235422 A CN201110235422 A CN 201110235422A CN 102255697 A CN102255697 A CN 102255697A
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portable terminal
via node
cooperation
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CN102255697B (en
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林子怀
刘扬
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Tianjin membrane technology industrial environment protection & Technology Co., Ltd.
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林子怀
刘扬
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Abstract

The invention discloses a distributed physical layer network coding modulation method for a multiple access channel in a wireless network. The method is implemented in a distributed physical layer network coding modulation way by utilizing a punctured convolutional coding digital phase modulation technology. In the method, a theoretical limit for a distributed system is deduced at the same time. A simulation result shows that the theoretical limit is in accordance with a simulation result value; and when a signal to noise ratio is increased, the simulation result is asymptotic to a theoretical limit value, thereby verifying the accuracy of a deduced theoretical value.

Description

The distributed physical-layer network coding modulator approach of multiple access channel in the wireless network
Technical field
The present invention relates to the cellular mobile network technology, be specifically related to be applicable to the coding and the modulator approach of the distributed physical layer network of multiple access channel in the wireless network.
Background technology
Distributed coding has attracted a large amount of researchers' concern as a kind of special chnnel coding cooperative communication network development mode.The structure theory of distributed coding has been applied to traditional channel coding, as document [B. Zhao and M. C. Valenti, " Distributed turbo codes:towards the capacity of the relay channel; " IEEE VTC ' 03-Fall, vol. 1, pp. 322 – 326, Oct. 2003.] disclosed Distributed T urbo sign indicating number, document [S. Yiu, R. Schober and L. Lampe, " Distributed space-time block coding, " IEEE Trans. Commun., vol.54, no.7, pp. 1195 – 2006, Jul. 2006.] disclosed distributed space time-code, document [A. Chakrabarti, A. Baynast, A. Sabharwal and B. Aazhang, " Low density parity check codes for the relay channel, " IEEE JSAC, vol. 25, no. 2, pp. 280 – 291, Feb. 2007.] disclosed distributed low-density checksum (LDPC) sign indicating number.Experimental result shows that above-mentioned distributed coding scheme can improve the reliability of a little transmitting to the radio channel of putting.
Above-mentioned distributed coding scheme is at small-scale clean culture junction network, and information is by list/multi-hop wireless junction network, transmits to single destination node from the single source node.For example under scene shown in Figure 1, a source portable terminal (MT) and other portable terminals (MT) cooperation transmit data by a via node (RN) to base station (BS).The traditional approach that transmits this information is by route, and the packet that receives is simply stored and transmitted to via node to the destination.
Document [R. Ahlswede, N. Cai, S. Y. R. Li, and R.W. Yeung, " Network Information Flow, " IEEE Trans. Inform. Theory, vol. 46, no. 4, pp. 1204 – 1216, July 2000.] propose a kind of network code (NC) method and substituted routing algorithm.In network code, via node can be encoded the packet of receiving from the multiple source portable terminal.Information behind the coding is sent to the destination subsequently.Experimental result shows, compares with traditional routing algorithm, and network code can improve network capacity and throughput.Because research and design (DNCC) theory of this distributed network passage sign indicating number just begins recently, many at distributed coding design and implementation process in the problem that runs into all also be not resolved.
Summary of the invention
The object of the present invention is to provide the distributed physical-layer network coding modulator approach of multiple access channel in a kind of brand-new wireless network.This method adopts collaboration type uplink distributed coding sign indicating number based on the puncture convolution code.The present invention has also analyzed the performance of system on this basis, derives the error rate theory analysis upper limit of the present invention.
Technical scheme of the present invention is as follows:
The distributed physical-layer network coding modulator approach of multiple access channel comprises the steps: in a kind of wireless network
1) the source portable terminal is encoded to transmitted codewords by the puncture convolution coder with packets of information, is broadcast to via node and cooperation portable terminal then;
2) via node receive from the signal waveform of source portable terminal with from the signal waveform of cooperation portable terminal, separate according to mark space, then alternately series connection generates new signal waveform;
3) the new signal waveform of Xing Chenging is deciphered by separating at the decoder of via node to be in harmonious proportion, and output needle is to the estimation code word of the combined coding device of source portable terminal and cooperation portable terminal;
4) the described estimation code word recursive system convolution coder that is admitted to via node carries out network code and carries out memoryless modulation, is sent to the base station then;
5) base station receives and does soft demodulation earlier after the signal waveform of via node emission and decode then.
Described step 2) in, if via node can be correct the data decode of source portable terminal, the portable terminal of then need not cooperating carries out cooperation transmission; If via node can not be correct the data decode of source portable terminal, then via node will send the instruction that requires the transmission identical data to the cooperation portable terminal, the cooperation portable terminal receives that the instruction back is after the data decode from the source portable terminal, utilize different puncture convolution coders to encode, send to via node then.
In the described step 3), the decoder of via node is the decoder at the combined coding device of source portable terminal and cooperation portable terminal.
In the described step 5), soft demodulation is to allow the signal waveform that receives through one group of waveform matched filter, the decoder that is sent to the base station from the value of this group filter output is deciphered, and the decoder of described base station is the decoder of the super grid coder formed at the recursive system convolution coder of puncture convolution coder that is distributed in source portable terminal and cooperation terminal and via node.
Useful technique effect of the present invention is:
The present invention is directed to wireless network and propose a kind of ul transmissions scheme of collaboration type, the present invention adopts distributed physical-layer network coding modulation system, utilizes puncture convolutional encoding digital phase modulation technology to realize.The present invention has derived a theoretical limit at this distributed system simultaneously.Simulation result shows that this theoretical derivation limit meets the simulation result value, when signal to noise ratio increases, and simulation result asymptotic theory limiting value, thereby the accuracy of the theoretical value that checking is derived.
Description of drawings
Fig. 1 has a source portable terminal, a cooperation portable terminal, the uplink system block diagram of a via node and a base station.
Fig. 2 is the simulation result of bit error rate of the present invention and the comparison diagram of the theory analysis upper limit.
Embodiment
Below by embodiment invention is described further.
The present invention considers is ul transmissions system among the radio honeycomb mobile network.Referring to Fig. 1, Fig. 1 shows and has a source portable terminal MT(A), a cooperation portable terminal MT(B), a via node RN(R) and the uplink system block diagram of a base station BS (C).There is a source portable terminal MT to send packet to base station BS in this system by via node RN.Herein, the present invention only with cellular mobile network as embodiment, in fact the present invention can be applied in all wireless networks, and is point-to-point such as wireless sense network, ad hoc(), WLAN (wireless local area network) etc., should not regard qualification as.
The cooperation transmission stage
The source portable terminal can be cooperated with other portable terminals and be carried out transfer of data.According to document [K.Doppler and M.Xiao, " Innovative concepts in peer-to-peer and network coding; " Tech. Rep. D1.3, CELTIC Telecommunication Solutions, 2009.], suppose to have direct link between source portable terminal MT and the cooperation portable terminal MT, but do not have direct link between base station BS and the portable terminal.The transmission of a packet can be divided into two time slots.At first time slot, source portable terminal MT encodes to information utilization puncture convolution coder earlier, then the packet behind via node RN and cooperation portable terminal MT broadcasting coding.Via node RN and cooperation portable terminal MT begin decoding.After cooperation portable terminal MT is correctly the decoding from the information of source portable terminal MT, utilize different puncture convolution coders that this information of having decoded is encoded again again.In the time of needs, the code word from the cooperation portable terminal will send to via node RN at second time slot.As shown in Figure 1, portable terminal MT in source uses puncture convolution coder C 1, and cooperation portable terminal MT uses puncture convolution coder C 2
If via node RN can be correct the data decode of source portable terminal MT, via node RN just the data message recompile modulation from source portable terminal MT after the decoding, is transmitted to base station BS then so.In this case, the source portable terminal MT cooperation transmission of portable terminal MT of need not cooperating.If via node RN can not be correct the data decode of source portable terminal MT, via node RN will send the instruction that requires the transmission identical data to cooperation portable terminal MT so, can send to via node RN then encoding with different encoders from the data of source portable terminal MT after cooperation portable terminal MT receives instruction.
Suppose all have identical code check k/n at each encoder of source portable terminal and cooperation portable terminal.For a system that has a source portable terminal and k-1 cooperation portable terminal, the unicode rate of k combined coding device will be 1/n so.The convolution coder of supposing all portable terminals has identical as document [J. G. Proakis, Digital Communication, McGraw-Hill, New York, third edition, 1995.] described constraint length (constraint length).According to document [A. J. Viterbi and L. K. Omura, Principles of Digital Communication and Coding, McGraw-Hill, New York, 1979.], be the convolution coder of 1/n for code check, the generator polynomial matrix
Figure 429852DEST_PATH_IMAGE001
, here
Figure 2011102354223100002DEST_PATH_IMAGE002
The time parameter
Figure 2011102354223100002DEST_PATH_IMAGE004
Belong to set 0,1}.High code check puncture convolution code (PCC) can obtain by the Binary Convolutional Code of other (parent) 1/n of its upper level of puncture.By using (the puncture matrix of n * p), P Mat, wherein p is the puncture cycle, realizes puncturing the operation of some coded identifications.Altogether transmitted bit number when establishing s here and being p for the puncture cycle, the PCC encoding rate is r=p/s.
The via node stage
Via node RN is aloft mixing from the signal waveform of source portable terminal MT with from the signal waveform of cooperation portable terminal MT of receiving, combined decoding then.This concrete air mix operating process is as follows: via node RN separates two signal waveforms according to mark space, and then alternately series connection generates new waveform, and this new waveform is deciphered by separating at the decoder of via node RN to be in harmonious proportion.This method is different from traditional physical layer network situation the method for the signal waveform stack that receives.The decoder of via node RN at be the combined coding device C of source portable terminal MT and cooperation portable terminal MT 1And C 2What this decoder was exported is at the combined coding device C of source portable terminal MT with cooperation portable terminal MT 1And C 2The estimation code word.A recursive system convolution (RSC) encoder that this estimation code word is fed to via node RN then carries out network code and carries out memoryless modulation.Here said by RSC carry out network code be meant will come from two data streams of source portable terminal MT and cooperation portable terminal MT mix by RSC, form a new data flow, different with XOR (XOR) operation in the legacy network coding, the present invention adopts RSC to carry out the network code operation.Rsc encoder and memoryless modulator can be seen as a digital coding Continuous Phase Modulation (CPM) device.At via node RN, rsc encoder will be from an output symbol in the associating portable terminal decoder as an input and generate a vector, and memoryless modulator will produce the waveform of a Channel Transmission with this vector.
The base station stage
Code word after the decoding is sent to base station BS (also being known as destination node) through recursive system convolution (RSC) encoder and after carrying out memoryless modulation.Base station BS receives to be done soft demodulation (Soft demodulation) earlier after the signal waveform of relaying node RN emission and begins decoding then, here said soft demodulation is meant and allows the signal waveform that receives through one group of waveform matched filter, be sent to decoder from the value of this group filter output and decipher, this decoder at be to be distributed in the super grid coder that the rsc encoder of the puncture convolution coder of source portable terminal MT and cooperation terminal MT and via node RN is formed.
Hereinafter will provide a systematic function theoretical upper limit under the situation that the channel condition and the employing maximum likelihood of additive white Gaussian noise (AWGN) detect (MLSD) algorithm.
The theory analysis upper limit
At via node, be distributed in the source portable terminal and the puncture convolution coder of cooperation portable terminal and the RSC of via node and formed a super grid coder.When the definition discrete time is j, the state of super grid coder
Figure 2096DEST_PATH_IMAGE005
For
Figure 2011102354223100002DEST_PATH_IMAGE006
, here
Figure 272671DEST_PATH_IMAGE007
With
Figure 2011102354223100002DEST_PATH_IMAGE008
When being illustrated respectively in discrete time and being j, the state of Joint Distribution convolution coder (JDCE) and the state of RSC.For a Joint Distribution convolution coder and the binary system total regression CPM system that has reasonable irreducible again modulation index h=K/P with m element, the state of super trellis encoder adds up to
Figure 962409DEST_PATH_IMAGE009
The input of associating terminal encoder has determined state exchange
Figure 2011102354223100002DEST_PATH_IMAGE010
The incoming symbol that also have rsc encoder relevant with this transfer process
Figure 615499DEST_PATH_IMAGE011
And an average vector, this average vector is to obtain through a complex set of filter process by the CPM waveform that makes transmission, these filters are complementary with transmitting.Foregoing can be referring to document [Z.Lin, Joint Source-Channel Coding using Trellis Coded CPM, Ph.D Thesis, Chalmers University of Technology, Gothenburg, Sweden, Jan. 2006, http://www.ce.chalmers.se/TCT.].
In the present invention, suppose that source node and cooperative node have identical transmitting power.If E bBe information bit power, N 0/ 2 is the power spectral density of two-sided additive white Gaussian noise.The probability of the mistake of the memoryless information source sequence of a puncture trellis coding CPM system will be followed following theorem 1.
Theorem 1: detect (MLSD) and the source information piece does not have under the condition of endless at maximum likelihood, the upper limit of the bit mistake code check of the digital phase modulation CPM system of a distributed puncture convolutional encoding that has a memoryless equiprobability distributed digital loop source sequence that disperses provides the upper limit by following formula:
（1）
Here
Figure 944850DEST_PATH_IMAGE013
Be minimum normalized square of Euclidean distance (NSED), It is dummy variable, according to document [T. Aulin, " Symbol Error Probability Bounds for Coherently Viterbi Detected Continuous PhaseModulated Signals; " IEEE Trans. Commun., vol. COM-29, no. 11, pp. 1707 – 1715, Nov. 1981.], r is the encoding rate of PRCC trellis coding, r=p/s.The average transmission equation is:
Figure 19116DEST_PATH_IMAGE015
（2）
Here
Figure 2011102354223100002DEST_PATH_IMAGE016
Be that state is when being j since the time , when NSED is d 2, length is
Figure 563361DEST_PATH_IMAGE019
And have
Figure 2011102354223100002DEST_PATH_IMAGE020
The quantity of all error events of individual mismark.The Q function is defined as follows:
Figure 432091DEST_PATH_IMAGE021
Below provide the proof of theorem 1.
Figure 2011102354223100002DEST_PATH_IMAGE022
Being designated as from discrete time is that j begins total bit mistake that all error events of back are produced.With a state arbitrarily, state s for example, , wherein S is a state space.If
Figure 2011102354223100002DEST_PATH_IMAGE024
For mistake begins when the time is j, initial condition is s, and length is that a l normalizing square Euclidean distance is (NSED) d 2
Figure 611848DEST_PATH_IMAGE020
For by error event
Figure 135233DEST_PATH_IMAGE024
The mismark that brings, initial condition and sequence are right
Figure 627394DEST_PATH_IMAGE025
Can express this error event fully
Figure 682069DEST_PATH_IMAGE024
Here
Figure 19509DEST_PATH_IMAGE027
With
Figure 2011102354223100002DEST_PATH_IMAGE028
It is the data sequence of two reconstructions.
For a puncture convolutional encoding and total regression Continuous Phase Modulation (CPM) system, with an error event Relevant NSED d 2May be calculated
Figure 538346DEST_PATH_IMAGE031
(6)
Here T is-symbol _ time interval, and
Figure 680703DEST_PATH_IMAGE033
, here
Figure 2011102354223100002DEST_PATH_IMAGE034
It is the difference phase state.
Figure 2011102354223100002DEST_PATH_IMAGE036
The operator of mould x,
Figure 284991DEST_PATH_IMAGE037
Be phase response, referring to document [J. B. Anderson, T. Aulin, and C. E. Sundberg, Digital Phase Modulation, Plenum Press, New York, 1986].
The desired value of the wrong bitrate that when zero-time j, causes by error event as shown in the formula:
Figure 2011102354223100002DEST_PATH_IMAGE038
(7)
Here
Figure 239171DEST_PATH_IMAGE039
With
Figure 2011102354223100002DEST_PATH_IMAGE040
Be two random vectors, their result space be the reconstruction signal sequence that might begin during for j in the time and,
Figure 612515DEST_PATH_IMAGE041
Be when state is s, have (NSED) d 2, length is the error event quantity of the total mismark of l when being τ, the desired value of formula (7) be since the time be all error events behind the j.
The encoding rate of supposing upper level (parent) convolution coder is k/ (k+1).Have 2 like this kIndividual branch road enters and leaves each state.For the digital source sequence of a discrete memoryless equal probability, that all begin with state s, to have length be that the sequence of l is contingent with probability, then releases following formula:
Figure 2011102354223100002DEST_PATH_IMAGE042
(8)
Conditional probability
Figure 446479DEST_PATH_IMAGE043
On be limited to
Figure 2011102354223100002DEST_PATH_IMAGE044
,
Here the Q equation is defined as
Figure 272483DEST_PATH_IMAGE045
,
Prove as follows: establish Be all zero-time be j, state is that s, length are
Figure 968038DEST_PATH_IMAGE019
Sequence
Figure 382839DEST_PATH_IMAGE047
Set.Note Be set
Figure 200753DEST_PATH_IMAGE046
Base.When
Figure 451737DEST_PATH_IMAGE049
The time, in set
Figure 872354DEST_PATH_IMAGE046
In have only two sequences
Figure 407241DEST_PATH_IMAGE051
With
Figure 2011102354223100002DEST_PATH_IMAGE052
Figure 327880DEST_PATH_IMAGE052
Decision region be half of signal space,
Figure 315428DEST_PATH_IMAGE053
Provided the error rate accurately
Figure 2011102354223100002DEST_PATH_IMAGE054
, d here 2Be to transmit
Figure 415102DEST_PATH_IMAGE055
With Between NSED.Therefore,
Figure 289648DEST_PATH_IMAGE057
, when
Figure 2011102354223100002DEST_PATH_IMAGE058
,
Figure 449365DEST_PATH_IMAGE052
Determining area between just less than the decision space half, draw thus
Figure 861892DEST_PATH_IMAGE059
Based on The above results and formula (8), consider all error events and use associating upper limit technology, according to document [A. J. Viterbi and L. K. Omura, Principles of Digital Communication and Coding, McGraw-Hill, New York, 1979.], can set On be limited to:
Figure 765257DEST_PATH_IMAGE061
(9)
For further reducing the computational complexity of (9), it is noted that CPM for a coding, some states are of equal value.Meaning of the equivalence here when two error events
Figure 2011102354223100002DEST_PATH_IMAGE062
With
Figure 9157DEST_PATH_IMAGE063
Begin when the time is j simultaneously, state is With
Figure 74196DEST_PATH_IMAGE065
, respectively by the identical sequence array
Figure 2011102354223100002DEST_PATH_IMAGE066
During generation, they are equal to.The grade here is both the mismark that error event has identical length, equal NSED and can produce equal number.If two states
Figure 787068DEST_PATH_IMAGE064
With Be equal to,
Figure 530213DEST_PATH_IMAGE067
According to above proof, the state of all puncture convolutional encoding CPM has puncture convolution coder equal state when the time is j,
Figure 953104DEST_PATH_IMAGE007
Be identical.
Figure 147413DEST_PATH_IMAGE009
In the individual coding total regression CPM state, have only 2 mIndividual state is unequal mutually.Therefore, (9) can be designated as again:
Figure 2011102354223100002DEST_PATH_IMAGE068
(10)
Divide other discrete memoryless source sequence for an independent same, encoder can begin at any s mUnder the lattice type state one of in individual.Because become when puncture is periodicity, Also depend on time j and the cycle variation.The state of a CPM coding when the time is j
Figure 283176DEST_PATH_IMAGE005
Equal 2 mThe probability of one of different conditions is among individual
Figure 142548DEST_PATH_IMAGE069
(11)
Suppose that source sequence is an endless, works as x, y〉0 use inequality, according to document [J. B. Anderson, T. Aulin, and C. E. Sundberg, Digital Phase Modulation, Plenum Press, New York, 1986.],
Figure 2011102354223100002DEST_PATH_IMAGE070
, make simultaneously , the symbol error rate upper limit can be decided to be
(12)
Here p is the puncture cycle of mentioning at second portion, and j=0 is meant the puncture beginning.
The left side of inequality (12) can be calculated by generating function.Will
Figure 613292DEST_PATH_IMAGE073
Be designated as at different conditions
Figure 686290DEST_PATH_IMAGE018
Under generating function
Figure 467295DEST_PATH_IMAGE075
Figure 563427DEST_PATH_IMAGE073
Be shown below:
Figure 2011102354223100002DEST_PATH_IMAGE076
（13）
Wherein
Figure 150398DEST_PATH_IMAGE014
Be dummy variable [14].The substitution following formula, equation (12) can be designated as:
Figure 77902DEST_PATH_IMAGE077
（14）
The average generating function here
Figure 2011102354223100002DEST_PATH_IMAGE078
Figure 29809DEST_PATH_IMAGE079
（15）
Arrive this, theorem 1 proof finishes.
By using the product state diagram, according to document [E. Biglieri, " High-level modulation and coding for nonlinear satellite channels; " IEEE Trans. Commun., vol. COM-32, pp. 616 – 626, May 1984.] and document [J. Shi and R. D.Wesel, " Efficient computation of trellis code generating function, " IEEE Trans. Commun., vol. 52, no. 2, pp. 219 – 227, Feb. 2004.], can obtain transmission equation One is that the product state of j can be defined as in the time
Figure 2011102354223100002DEST_PATH_IMAGE080
, here
Figure 738319DEST_PATH_IMAGE005
Be the encoding state of CPM coded system,
Figure 785909DEST_PATH_IMAGE081
It is decoded state.The state conversion process
Figure 2011102354223100002DEST_PATH_IMAGE082
Just be expressed as
Figure 801112DEST_PATH_IMAGE083
（3）
Figure 871836DEST_PATH_IMAGE085
With
Figure 2011102354223100002DEST_PATH_IMAGE086
Represent mismark quantity and NSED. respectively
Figure 2011102354223100002DEST_PATH_IMAGE088
Expression has NSED
Figure 613659DEST_PATH_IMAGE086
The quantity in path,
Figure 515756DEST_PATH_IMAGE085
It is the mismark in this state exchange.
For the CPM of puncture trellis coding, the error rate only depends on the output of the convolution coder that punctures.In other words, it is right that it is independent of the state of CPM
Figure 996415DEST_PATH_IMAGE089
In addition, according to document [J. B. Anderson, T. Aulin, and C. E. Sundberg, Digital Phase Modulation, Plenum Press, New York, 1986.], NSED d 2The state difference that only depends on CPM
Figure 2011102354223100002DEST_PATH_IMAGE090
The product state has just reduced like this.For the CPM system of total regression, the product state of minimizing is
Figure 164223DEST_PATH_IMAGE091
, here
Figure 2011102354223100002DEST_PATH_IMAGE092
It is the phase difference state.All the product states of CPM system that have the CPM coding of total regression like this are exactly
Figure 834370DEST_PATH_IMAGE093
The product state of CPM coding can be divided into initial condition, transmission state and done state.The initial condition of a product state is defined as the beginning of error event, when done state is defined as the end of error event.The condition of initial condition and done state is respectively
Figure DEST_PATH_IMAGE094
With
Figure 404022DEST_PATH_IMAGE095
Other states are transition status.
With
Figure 55584DEST_PATH_IMAGE096
Represent from an initial condition
Figure 163217DEST_PATH_IMAGE018
The one state-transition process that goes on foot transmission state when the time is j, Bj represents by the transition process of transmission state to done state, Cj be illustrated in the time when being j transmission state one go on foot the process of transmission state.
Figure 371475DEST_PATH_IMAGE097
Expression is from an initial condition
Figure 982585DEST_PATH_IMAGE018
One step arrived the transition process of done state.According to document [J. B. Anderson, T. Aulin, and C. E. Sundberg, Digital Phase Modulation, Plenum Press, New York, 1986.], transmission equation can calculate with following formula:
Figure DEST_PATH_IMAGE098
（4）
Here 1 is that an all elements is 1 vector, and I represents unit matrix.
Equation (1) can be expressed as again:
Figure DEST_PATH_IMAGE099
（5）
Here
From formula (5) as can be seen, minimum NSED
Figure 753183DEST_PATH_IMAGE013
With
Figure DEST_PATH_IMAGE101
(have
Figure 82533DEST_PATH_IMAGE013
Error event quantity) determining the performance of the asymptotic symbol error rate of system,
Figure 94483DEST_PATH_IMAGE013
It is big more,
Figure 560099DEST_PATH_IMAGE101
More little, the progressive symbol error rate performance of system is good more.In the present invention, the design standard of best puncture matrix is according to whether producing maximum
Figure 819042DEST_PATH_IMAGE013
Realize.
Simulation result
The present invention under Gauss's additive white noise passage emulation the system of a plurality of employing different distributions formulas codings.In first system, the encoder of source portable terminal is that 1 parent nonsystematic convolutional encoding obtains by the puncture code check, and the generator polynomial of this parent convolutional encoding is The encoder of cooperation portable terminal is to be that 1 generator polynomial is by the puncture rate
Figure DEST_PATH_IMAGE105
Parent nonsystematic convolutional encoding obtain.Therefore, from via node, the combined coding device of source node and cooperation portable terminal is to be by one the generator polynomial of 1/2 rate of puncturing
Figure DEST_PATH_IMAGE107
The parent nonsystematic convolutional code generate.Table 1 has been listed the difference puncture matrix Pmat of different system, and puncture matrix Pmat is by all possible puncture pattern of exhaustive search, and the least square Euclidean distance d that can provide maximum that selects 2 MinThe puncture matrix.In table 1, the puncture matrix provides for example (3,5) with octadic form 0The puncture matrix form of representative is [011; 101] 0 be the position of the symbol that is punctured accordingly wherein.The puncture convolutional encoding of using in the emulation is that the generator polynomial by 1/2 rate that punctures is
Figure 261787DEST_PATH_IMAGE107
With
Figure DEST_PATH_IMAGE109
The parent nonsystematic convolutional code generate.Also listed file names with the d of different system in the table 1 2 Min, and observe symbolic number N B, N BThe CPM system that is meant coding reaches the required observation symbol quantity of minimum euclidean distance, and foregoing is referring to document [J. B. Anderson, T. Aulin, and C. E. Sundberg, Digital Phase Modulation, Plenum Press, New York, 1986.].
Table 1
Figure DEST_PATH_IMAGE110
The value of corresponding each signal to noise ratio in emulation, the block of information that to adopt 100 length be 8000 bits is carried out emulation.Fig. 2 has shown the simulation result and the theoretical upper limit of the bit error rate (BER) of distributed network code modulation system of the present invention.Can see that simulation result meets the theoretical upper limit of derivation, when signal to noise ratio increased, simulation result was gradually near theoretical upper limit.
Fig. 2 is simultaneously displayed on identical E b/ N 0Condition under, adopt the bit error rate performance of parent convolution code always to be better than the convolution code that punctures accordingly.For example, at E b/ N 0In the time of=8, the BER performance of parent convolution code (rate be 1/2) is better than corresponding puncture convolution code.Again for example, for producing multinomial be
Figure 874165DEST_PATH_IMAGE109
The father's convolution code and the puncture convolution code of its corresponding 3/4 rate, equal 10 at the ordinate bit error rate -4The time, relatively with the solid line (the puncture convolution code of 3/4 rate) of the solid line (parent convolution code) of circle and band x number, the solid line (parent convolution code) of band circle is at BER=10 -4The time SNR=8dB, and the solid line (the puncture convolution code of 3/4 rate) of band x symbol is at BER=10 -4The time SNR=12dB, the performance gain of parent convolution code is probably about 4 decibels.
Above-described only is preferred implementation of the present invention, the invention is not restricted to above embodiment.Be appreciated that other improvement and variation that those skilled in the art directly derive or associate under the prerequisite that does not break away from basic design of the present invention, all should think to be included within protection scope of the present invention.

Claims (4)

1. the distributed physical-layer network coding modulator approach of multiple access channel in the wireless network is characterized in that, comprises the steps:
1) the source portable terminal is encoded to transmitted codewords by the puncture convolution coder with packets of information, is broadcast to via node and cooperation portable terminal then;
2) via node receive from the signal waveform of source portable terminal with from the signal waveform of cooperation portable terminal, separate according to mark space, then alternately series connection generates new signal waveform;
3) the new signal waveform of Xing Chenging is deciphered by separating at the decoder of via node to be in harmonious proportion, and output needle is to the estimation code word of the combined coding device of source portable terminal and cooperation portable terminal;
4) the described estimation code word recursive system convolution coder that is admitted to via node carries out network code and carries out memoryless modulation, is sent to the base station then;
5) base station receives and does soft demodulation earlier after the signal waveform of via node emission and decode then.
2. according to the distributed physical-layer network coding modulator approach of multiple access channel in the described wireless network of claim 1, it is characterized in that: described step 2), if via node can be correct the data decode of source portable terminal, the portable terminal of then need not cooperating carries out cooperation transmission; If via node can not be correct the data decode of source portable terminal, then via node will send the instruction that requires the transmission identical data to the cooperation portable terminal, the cooperation portable terminal receives that the instruction back is after the data decode from the source portable terminal, utilize different puncture convolution coders to encode, send to via node then.
3. according to the distributed physical-layer network coding modulator approach of multiple access channel in the described wireless network of claim 1, it is characterized in that: in the described step 3), the decoder of via node is the decoder at the combined coding device of source portable terminal and cooperation portable terminal.
4. according to the distributed physical-layer network coding modulator approach of multiple access channel in the described wireless network of claim 1, it is characterized in that: in the described step 5), soft demodulation is to allow the signal waveform that receives through one group of waveform matched filter, the decoder that is sent to the base station from the value of this group filter output is deciphered, and the decoder of described base station is the decoder of the super grid coder formed at the recursive system convolution coder of puncture convolution coder that is distributed in source portable terminal and cooperation terminal and via node.
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