# Modelling of Wireless channel

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#### er.rakeshjain

##### Newbie level 4
modelling a wireless channel

Dear all,
I have simulated WiMAX Transmitter and receiver in Matlab. Now I want to introduce channel effect between tx and Rx. Pls guide me to model the channel in MATLAB.

#### Joatt

##### Junior Member level 1
There are two effects that you should consider in your channel: noise and passband limitation (banwidth).

If you are working on Simulink, you can add a "White Gaussian Noise" generator to your circuit, and a bandpass filter for passband limitation (The passing bandwith of the filter is the working frequency rane of your antenna).

However, if you are using Matlab codes only, you can generate a random noise by a code similar to:
Code:
noise=0.7*randn(size(t));

and then add it to your transmitted signal. Then, apply the following filter on your transmitted signal:
Code:
nsignal = signal + noise; % transmitted signal after adding the noise
flo = 2e9;
fup = 3e9; % assuming here that freq. range of the antenna is 2~3 GHz
fc = (flo + fup)/2;
fs = 4.5e9; % stopband frequency
Wp = [flo fup]/(fs/2); % normalized passband interval
Ws = [(fc/2) (fc+(fc/2))]/(fs/2); % normalized stopband interval
Rp = 3; % 3-dB attenuation at passband
Rs = 30; % 30-dB attenuation at stopband
[n,Wn] = buttord(Wp,Ws,Rp,Rs); % Butterworth filter
[b,a] = butter(n,Wn);
channelsignal = filter(b, a, nsignal); % The resulting signal

Regards

#### er.rakeshjain

##### Newbie level 4
Thanks for your reply. I will try it.

#### laxmi

##### Newbie level 1
dear all
i am doing thesis in k- best algorithm for mimo detection. for this i want matlab simulation environment, where transmit signals, which channel, what noise etc.

#### er.rakeshjain

##### Newbie level 4
How can I add Fading effect and Delay Spread in Channel using Matlab.
How will I estimate channel at the receiver using pilots. I used pilots in my transmitted signal but at the receiver side simply extracting them. How pilots will be used to estimate channel and apply correction to the signal.

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