信道编码LDPC和Turbo文档格式.docx

信道编码LDPC和Turbo文档格式.docx

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LTEusesaturbocoderasachannelcoder.Researchtheliteraturetoexplainthischoice.Whatisyourpersonalviewonthischoice?

（maximumlength1000words）.

Turbocodingisanevolutionoftheconvolutionalcodingtechnologyusedinallpreviousstandardswithimpressivenear-channelcapacityperformance.ManyfactorsledtothechoiceofturbocodinginLTE.Thefirstisthenear-Shannon-boundperformanceofturbocoders.Givenasufficientnumberofiterationsinturbodecoding,turbocodescanhaveaBERperformancefarinexceedsofthoseofconventionalconvolutionalcoders.Furthermore,theylendthemselvestoadaptation,duetotheuseofaninnovativerate-matchingmechanism.

Inmyopinion,thisisawisechoice.TheLTEisdesignedtoprovidehigherdatarates,improvedpowerefficiency,lowlatencyandbetterqualityofservice.Thisrequestsanexcellent 

channelcodingmethod.Turbohasanear-Shannon-boundperformanceanditcanprovideavarietyofcodingrates.Withthecontinuousoptimizationofthedecodingalgorithmandthecontinuousimprovementofhardwareperformance,turbodecodingspeedbecomesfasterandfaster.SoturboisverysuitableforLTE.

Appendix1:

main.m

clear

clc

%%Task3

%WriteascriptthatusesthefunctiontoplotthesimulatedBERofthetransceiver

%asafunctionoftheenergyperbittonoisepowerspectraldensityratio（Eb/N0）.

EbNoTask3=0:

0.5:

2.5;

%SettheEbNoforsimulation

maxNumErrs=0.5*10^7;

%Setthemaximumnumberoferrorbits

maxNumBits=10^7;

%Setthenumberofsimulationbits

ber_all=zeros（length（EbNoTask3）,1）;

%Initializeber

forii=1:

length（EbNoTask3）

EbNo=EbNoTask3（ii）;

%GetthecurrentEbNo

[ber,bits]=qpsk_turbo（EbNo,maxNumErrs,maxNumBits）;

%Callthefunction

ber_all（ii）=ber;

%Recordtheber

end

%Plot

figure

（1）

semilogy（EbNoTask3,ber_all,'

-r*'

'

lineWidth'

2）;

legend（'

Turbo,NumIteration=2'

0）;

xlabel（'

Eb/N0（dB）'

）;

ylabel（'

BER'

title（'

Task3'

gridon;

%%Task4

%Increasethenumberofiterationsintheturbodecoder（usethreeadditionalvalues）.

EbNoTask4=0:

0.3:

1.2;

iteration=2:

5;

%Setiteration

ber_ite=zeros（length（EbNoTask4）,length（iteration））;

length（iteration）

forjj=1:

length（EbNoTask4）

EbNo=EbNoTask4（jj）;

[ber,bits]=qpsk_turbo_ite（EbNo,maxNumErrs,maxNumBits,iteration（ii））;

ber_ite（jj,ii）=ber;

end

figure

（2）

semilogy（EbNoTask4,ber_ite（:

1）,'

-bs'

EbNoTask4,ber_ite（:

2）,'

-go'

3）,'

-k+'

4）,'

NumIteration=2'

NumIteration=3'

NumIteration=4'

NumIteration=5'

Task4'

%%Task5

%ReplacetheturbocoderbyanLDPCcoder.

EbNoTask5=-0.2:

0.2:

0.4;

maxNumBits1=[10^5,10^6,10^6,10^7];

ber_ldpc=zeros（length（EbNoTask5）,1）;

length（EbNoTask5）

EbNo=EbNoTask5（ii）;

[ber,bits]=qpsk_ldpc（EbNo,maxNumErrs,maxNumBits1（ii））;

ber_ldpc（ii）=ber;

figure（3）

semilogy（EbNoTask5,ber_ldpc,'

-g+'

LDPC'

Task5'

Appendix2:

qpsk_turbo.m

function[ber,bits]=qpsk_turbo（EbNo,maxNumErrs,maxNumBits）

%%Constants

FRM=2048;

%Sourcebitsforonce

Trellis=poly2trellis（4,[1315],13）;

%Convertconvolutionalcodepolynomialstotrellisdescriptionforturbo

Indices=randperm（FRM）;

%Generatearandominterleavingtableforturbo

M=4;

k=log2（M）;

%Modulationorderandmodulationbits

R=FRM/（3*FRM+4*3）;

%Coderateis1/3and'

4*3'

isthelengthoftailbit.

snr=EbNo+10*log10（k）+10*log10（R）;

%CalculatetheSNR.SNR=EbNo+10*log10（Rb/Rs）=EbNo+10*log10（k）+10*log10（R）

noise_var=10.^（-snr/10）;

%Calculatethenoisepower

%%Initializations

persistentModulatorAWGNDeModulatorBitErrorTurboEncoderTurboDecoder%Definepersistentvariable

ifisempty（Modulator）%If'

Modulator'

hasnotdefined.

Modulator=comm.QPSKModulator（'

BitInput'

true）;

%GettheQPSKmodulatorhandleandsetinputdataasbits

AWGN=comm.AWGNChannel;

%GettheAWGNchannelhandle

DeModulator=comm.QPSKDemodulator（'

BitOutput'

true,...%GettheQPSKdemodulatorhandleandsetoutputdataasbits

'

DecisionMethod'

Log-likelihoodratio'

...%DecisionMethodisLog-likelihoodratio

VarianceSource'

'

Inputport'

%Specifythesourceofthenoisevarianceas'

Inputport'

BitError=comm.ErrorRate;

%GetErrorRatehandle.

TurboEncoder=comm.TurboEncoder（...%Gettheturboencoderhandle

TrellisStructure'

Trellis,...%Setthepolynomials

InterleaverIndices'

Indices）;

%Settheinterleavingtable

TurboDecoder=comm.TurboDecoder（...%Gettheturbodecoderhandle

Indices,...%Settheinterleavingtable

NumIterations'

%Specifethenumberofdecodingiterations

%%Processsingloopmodelingtransmitter,channelmodelandreceiver

AWGN.EbNo=snr;

%Setthesignal-to-noiseratioofthechannel

numErrs=0;

numBits=0;

results=zeros（3,1）;

%Initializethenumberoferrorbits,thenumberofsimulatedbits,andthesimulationresults

while（（numErrs<

maxNumErrs）&

&

（numBits<

maxNumBits））%WhenthenumberoferrorbitsislessthanmaxNumErrsandthenumberofsimulatedbitsislessthanmaxNumBits

%Transmitter

u=randi（[01],FRM,1）;

%Randombitsgenerator

encoded=TurboEncoder.step（u）;

%TurboEncoder

mod_sig=Modulator.step（encoded）;

%QPSKModulator

%Channel

rx_sig=AWGN.step（mod_sig）;

%AWGNchannel

%Receiver

demod=DeModulator.step（rx_sig,noise_var）;

%Soft-decisionQPSKDemodulator

decoded=TurboDecoder.step（-demod）;

%TurboDecoder

y=decoded（1:

FRM）;

%Computeoutputbits

results=BitError.step（u,y）;

%UpdateBER

numErrs=results

（2）;

%Updatethenumberoferrorbits

numBits=results（3）;

%Updatethenumberofsimulatedbits

%%Cleanup&

collectresults

ber=results

（1）;

bits=results（3）;

%Returntheresults

reset（BitError）;

Appendix3:

qpsk_turbo_ite.m

function[ber,bits]=qpsk_turbo_ite（EbNo,maxNumErrs,maxNumBits,numIteration）

TurboDecoder=comm.TurboDecoder（...%Get