How can I use a Rician simulation on Passband?

Hi,

I am developing a Rician simulation for an OTFS modem and implementing it on a signal that has been modulated to passband. I am using the 'comm.RicianChannel' function for this purpose.

However, I encountered an issue: the output of this function is complex, as if it were in baseband, while I need the output to be in passband and real-valued.

I attempted to create an analytic signal and then use only the real part after applying the channel, but I am uncertain if this approach is correct.

Could you please advise on how to adjust the function or filter to work with passband signals and obtain a real-valued output? Any suggestions or guidance would be greatly appreciated.

Thank you.

Code example of the Rician channel:

%% Configure a Rician channel object
ricChan = comm.RicianChannel( ...
    'SampleRate',fs, ...
    'PathDelays',delayVector, ...
    'AveragePathGains',gainVector, ...
    'KFactor',KFactor, ...
    'DirectPathDopplerShift',specDopplerShift, ...
    'MaximumDopplerShift',maxDopplerShift, ...
    'RandomStream','mt19937ar with seed', ...
    'Seed',randi([1 1000],1) , ...
    'PathGainsOutputPort',true);

%% Apply Rician channel object on the modulated data
for k = 1:numberOfReceivers
    temp=[zeros(round(DelayTime(k) * fs),1); sigIn ; zeros(round(max(DelayTime * fs)) - round(DelayTime(k) * fs),1)];
    noise = Pn * randn(1, size(sigIn, 2));
    sigOut(:,k)=ricChan(temp);
    sigOut(:,k)=sigOut(:,k)+noise;    
end

Answer 1

[Pratyush]

Hi Yedidia,

To adapt a simulation for a passband and real-valued output when using MATLAB's "comm.RicianChannel", which inherently outputs complex baseband signals, follow these steps:

• Ensure your input ("sigIn") is in baseband.
• Apply the channel effects using "comm.RicianChannel" to the baseband signal.
• After channel application, modulate the signal back to passband frequency ("fc") using a carrier wave. This step converts the signal from baseband to passband.
• Use the real part of the modulated signal as your final, real-valued passband output.

The process involves applying the channel effects at baseband and then shifting the signal to passband, ensuring the output matches the physical representation of passband signals.

[Yedidia Ovadia]

Thanks for the answer Pratyush!