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space time block code of book mohinder expalanation required

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shakeel006

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hello all
i am new to space time coding .the following is 1 Tx and 2 RX code for space time block code.i need very clear and easy explanation of the following code.like what is meaning of frame length and packet size for 1 Tx and 2 RX code
%SNR upto 20 dBs
EbNo=[0:2:20];

%N, M: number of transmit and receive antennas

N=no_tx_antennas;
M=no_rx_antennas;

%initialize count
idx = 1;

h=waitbar(0,'Percentage Completed');
set(h,'Position',[230 60 275.25 56.25]);
set(h,'name','Please wait...');
wb=9.09;

for SNR=EbNo
sigma=0.5/(10^(SNR/10));

% Num -> number of packets
for packet_count=1:Num

% we are interested in transmitting 'K' SYMBOLS not bits. Hence, K*2 for QPSK
% etc.
switch (modulation)
case 'BPSK '
data=randint(K,N);
BIT=1;
case 'QPSK '
data=randint(K*2,N);
BIT=2;
case '8PSK '
data=randint(K*3,N);
BIT=3;
case '16QAM'
data=randint(K*4,N);
BIT=4;
otherwise
disp('No Modulation')
end

tx_bits=data.';
[temp s P]=tx_modulate(tx_bits,modulation);

%ready to transmit symbols of length 'K'
X=temp.';
fr_length=length(X);

% MRC
x0=X;

% form the channel matrix
if channel_model=='AWGN '
Hr=ones(fr_length,M);
else
Hr=(randn(fr_length,M)+j*randn(fr_length,M))/sqrt(2);
end


%transmission matrix
H=reshape(Hr,fr_length,M);
Habs=sum(abs(H).^2,2);

%received signal per receiver antenna
r1=sum(H:),1).*x0,2)/sqrt(N)+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));
r2=sum(H:),2).*x0,2)/sqrt(N)+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));

% demodulate the received signals
z1=r1.*conj(H:),1))+r2.*conj(H:),2));

%uncoded(1,1)
r01=H:),1).*x0+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));

%form estimates
for m=1:p
d01:),m)=abs(r01-H:),1)*s(m)).^2; %uncoded signal

%coded signals
d1:),m)=abs(sum(z1,2)-s(m)).^2+(-1+sum(Habs,2))*abs(s(m))^2;
end

% determine the minimum of estimates

%decision for detecting uncoded
[y0,i0]=min((d01),[],2);
s0d=s(i0).';
clear d01

%decision for detecting s1
[y1,i1]=min((d1),[],2);
s1d=s(i1).';
clear d1

% form received symbols
Xd=[s1d];

%determine symbol errors
error_un(packet_count)=sum(X:),1)~=s0d);% for uncoded
temp1=X>0;
temp2=Xd>0;
error(packet_count)=sum(sum(temp1~=temp2));% for coded
end% end of FOR loop for "packet_count"
%calculate FER, SER and BER for current idx

%for uncoded signal
SER_uncoded(idx)=sum(error_un)/(Num*K);
BER_uncoded(idx)=SER_uncoded(idx)/BIT;
FER_uncoded(idx)=SER_uncoded(idx)*K;

%for coded signal
SER(idx)=sum(error)/(Num*K);
BER(idx)=SER(idx)/BIT;
FER(idx)=SER(idx)*K;

%increment idx
idx=idx + 1;

str_bar=[num2str(wb) '% Completed'];
waitbar(wb/100,h,str_bar);
wb=wb+9.09;

end% end of FOR loop for SNR
close(h);

Best Regard
Shakeel
 

mimomod

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In communication, usually data is transmitted in blocks (frames). One block of data consists of many symbols determined by the standard. But for simulation purpose, you just need to assign any reasonable number of symbols for one block, e.g. 100 until 500 symbols per block.

In the simulation frame length = packet size.

For simulation you usually must generate many frames. Take for example 1000 frames.

best
 

vkekk

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Re: space time block code of book mohinder expalanation requ

Dear Mimomod

1. Suppose , In vBlast the length of the data is 9000 means what it represent i.e whether symbols or block length..

2. what are the differences between receiver , equalizers , detector and decoder in the communication system.

3. What is Maximum likelihood receiver and how it differs from rake receiver?


Please help me to get these information...
 

mimomod

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1. I guess it refers to the number of symbols. Note that for simulation purpose, it is common to consider only number of symbols. But if you want to be more realistic as defined by a standard, then you divide symbols into blocks.

2. Receiver consists of several sub-systems, including equalizer, detector, decoder. Equalizer is a subsystem responsible to inverse the channel effect. Detector is a subsystem responsible to convert received symbols into information data (message signal). Decoder is a subsystem to reverse the effect of encoder at transmitter, e.g. channel decoder to inverse channel encoder, etc.

3. ML receiver is an optimum receiver based on maximum likelihood criterion. Rake receiver is one of suboptimum receiver used mainly in CDMA with the basic idea is to get multiple copies of transmitted signal to imporove the reception quality. It is too long to explain in detail. Please refer to textbooks like Digital Communication by Proakis.
 

vkekk

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Re: space time block code of book mohinder expalanation requ

kkkk...
 

vkekk

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Re: space time block code of book mohinder expalanation requ

Please help me , I need to give presentation...... urgent
 

mimomod

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Sorry vkekk,

I am not able to check it. Indeed I know something about MIMO, but my knowledge will not be enough to give assesment for your project. Is it better if you discuss it with your supervisor?

best
 

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