Htlp me matlab code for performace of multihop with fixed relay

David83 said:

What is the relaying mode of the relays?

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David83 said:

Do you know how to do simulation for two hops?

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David83 said:

Outage is defined as following: the instantaneous SNR drops below a certain threshold. So, you need two things: the instantaneous SNR and the threshold. The threshold is predetermined, say 0 dB. Now you need to find the instantaneous SNR, which in your case will be the equivalent SNR of all hops. I do not remember it, but in the literature you can find the formula of the equivalent SNR of a multihop relaying system in terms of the SNR of individual hops. So, now all you need to do is to generate the individual hops' SNRs. For example, in case of Rayleigh fading, the instantaneous per hop SNR is exponentially distributed. So, generate L (number of hops) exponential random variables, and substitute them in the equivalent SNR. Then compare the equivalent SNR with the threshold. Repeat this process for a number of iterations to get smooth curve. For example for the case of two hops I would write the following code

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David83 said:

Outage is defined as following: the instantaneous SNR drops below a certain threshold. So, you need two things: the instantaneous SNR and the threshold. The threshold is predetermined, say 0 dB. Now you need to find the instantaneous SNR, which in your case will be the equivalent SNR of all hops. I do not remember it, but in the literature you can find the formula of the equivalent SNR of a multihop relaying system in terms of the SNR of individual hops. So, now all you need to do is to generate the individual hops' SNRs. For example, in case of Rayleigh fading, the instantaneous per hop SNR is exponentially distributed. So, generate L (number of hops) exponential random variables, and substitute them in the equivalent SNR. Then compare the equivalent SNR with the threshold. Repeat this process for a number of iterations to get smooth curve. For example for the case of two hops I would write the following code

Code:

clear all;
clc;

SNRdB=0:20;
SNR=10.^(SNRdB./10);

N=10;%Number of outages to find at each SNR point
ythdB=0;% Threshold in dB
yth=10.^(ythdB./10);

Out1=zeros(length(SNR),1);
Count1=zeros(length(SNR),1);

Out2=zeros(length(SNR),1);
Count2=zeros(length(SNR),1);

for ii=1:length(SNR)
    while Out1(ii)<=N || Out2(ii)<=N
        Count1(ii)=Count1(ii)+1;
        Count2(ii)=Count2(ii)+1;
        
        y1=exprnd(SNR(ii),1,1);%SNR of the first hop
        y2=exprnd(SNR(ii),1,1);%SNR of the second hop
        y0=exprnd(SNR(ii),1,1);%SNR of the direct link

        yeq1=y0+(y1*y2/(y1+y2+1));%Equivalent SNR in the presence of direct link with MRC at D
        yeq2=(y1*y2/(y1+y2+1));% Equivalent SNR in the absence of direct link

        if yeq1<=yth
            Out1(ii)=Out1(ii)+1;
        end
        if yeq2<=yth
            Out2(ii)=Out2(ii)+1;
        end
    end
end
semilogy(SNRdB,Out1./Count1,SNRdB,Out2./Count2)
axis([0 20 10^-5 1])
legend('With Direct Link','Without Direct Link')

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David83 said:

Usually, if you you have multiple relays in series, it is called multihop. If you have relays in parallel it is called multi-branch dual hop system. Just to set the terminology.

Do you know the math behind the curves? What kind of receiver was used? MRC or selection combining (SC)? If you know the mathematical equations, having the example I provided, it is easy to do.

I prefer to write down your own code, and discuss it, instead of asking me to "help you", expecting me to give you the code ready.

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David83 said:

You have the equivalent SNR as in (1). You just have the summation that is different than the one relay case. All you have to do is to generate different independent equivalent SNR per relay as in the code I gave you, and sum them up with the SNR of the direct link to get the overall equivalent SNR. It is straightforward.

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robintane said:

Yes, I know
I can simulate BER for 1 hop, two hops, ...
But I don't know how to simulate Outage Probability for 1 hop , 2 hops .... Can you help me this problem
Can you talk with me via gmail chat : nguyenkimhieuha

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