# Channel environment, impulse response question

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#### Thommer

##### Junior Member level 1
Hello!

I have implemented in matlab some classical channel equalization methods
(I used AWGN,BPSK). I have to make BER vs SNR simulations and should do this
in different channel environments (rural, hilly, urban..etc).
I'm looking for the corresponding impulse response values for them, but so far I
regards,
Thommer

#### Gandharva

##### Junior Member level 3
hi,
even if you find the impulse responses for such cases (which are readily available in the net) how will you simulate the channel?. for this you can use "Multipath rayleigh fading channel" or "rician fading channel" blocks readily available in Matlab.
The effect of Equalization on BER exists only when the channel is frequency selective, to make a channel frequency selective you must have multipath channel.

#### Thommer

##### Junior Member level 1
So this means, If I want to simulate the urban, rural..etc environment, instead of the AWGN model (with ISI as well (h)) I have to use those channel models you mentioned? I simply thought that I only change the impluse response values (to something that I'm looking for) and then I'll get the proper values for the different environments...
Thommer

#### Gandharva

##### Junior Member level 3
hi thommer,

if you use the "Multipath rayleigh fading channel" , the block itself gives you a means by which one can mention the delays and gains of each tap. so, this means you dont need to use the channel transfer function "h". In addition to this you can use the AWGN noise after this block.

I hope you get it.. happy learning..

#### Thommer

##### Junior Member level 1
Thanks for your answer, but I have the code now I only need the different impulse response values (I was told to solve the problem in this way)
regards,
Thommer

#### amihomo

##### Full Member level 5
hi, here is the impulse responses of BU and HT channels:

BU(t)= exp(-t) , 0<= t<2 (t in µS)
0.5exp(5-t) , 5<= t<10
0 ,otherwise

HT(t) = exp(-3.5t) , 0<= t<2 (t in µS)
0.1exp(5-t) , 15<= t<20
0 ,otherwise

bye

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