I am traying to simulate a frequency selective fading channel in Matlab and I have faced with some issue/questions during the implementation.
It is a DSSS (BPSK) modulation and the code is organized in packets (5000 packets) of 2550 symbols.
The channel that i want to simulate has the next parameters:
SamplingRate=50e-9; t_coh=30e-6; maxDopplerShift = 1/(t_coh); AvGain=[-3 0 -15 -7 -10 -15 -50]; PathDelay=[0 50 100 150 200 250 300]*1e-9;
My first approach was using the rayleighchan function.
chan=rayleighchan(SamplingRate,maxDopplerShift,PathDelay,AvGain);
I use filter(h,1,tx_modulated) in a for loop for each packet. Also, I reset the channel after every loop.
chan.reset; %For use different Rayleigh channel in each packet Paths = chan.PathGains;
Why reset? Because i assume that if i want to get the bit error rate simulating and "infinite" time, the channel time variance doesn't matter. I mean if i have a simulation of time varying channel during "infinite" time is the same as having the same channel resetting randomly.
My second approach is using Rayleigh channel object
chan = comm.RayleighChannel(...);
In this simulation, when I pass the data in the channel the taps gains changed so i assume that its like applying a time variant simulation. I see that the the impulse response taps and the frecuncy response changes slowly during all simulation. So, in my understanding depending on the initial channel configuration the BER can be worse or better that the first approach. I mean, the frequency response can be worse or better than the mean of the first approach. I assume that if i did and "infinite" simulation the result will be the same.
I don't know if my assumptions are correct, hope someone could help me.
Thanks,
Dear Mikel,
The results will be the same when the impulse response of the channel has the same dependence on the time. So, what is required is to display the impulse response of the channel with time.
The channel which has more rapid changes will have more bit error rate.
You can the simulation under the two cases and compare the time dependence of the channel impulse response and the bit error rate.
Best wishes
Dear Mikel,
The results will be the same when the impulse response of the channel has the same dependence on the time. So, what is required is to display the impulse response of the channel with time.
The channel which has more rapid changes will have more bit error rate.
You can the simulation under the two cases and compare the time dependence of the channel impulse response and the bit error rate.
Best wishes
Thanks for your answer Abdelhalim abdelnaby Zekry!!
So in short; saying "The BER of underspread (static) channel simulation, will be the same as same changing (no static) channel over and "infinite" amount of time" is a correct statement?
Hi Mikel,
You may also follow a Matlab example related to your query, such as https://www.mathworks.com/matlabcentral/answers/502145-time-variant-frecuency-selective-fading and answers on the right hand side of Matlab file.
Another study related to your problem is in RG : Article Equalization of linearly frequency-selective fading channels
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