Hi lc,
Please see my response to your posted questions below.
Question: I am confused that why the output signal of the object have the same length with the input signal?
The output signal of the comm.RicianChannel object having the same length as the input signal is a deliberate design choice to ensure that fading effects are accurately applied while preserving the structure and timing of the transmitted data in OFDM simulation which helps maintain consistency and reliability in communication systems when modeling fading channels.
Question: I mean that if we have a fading channel response, the conv result will make the signal longer(for delay reason), is that right?
Yes, utilizing the comm.RicianChannel object for a fading channel in your OFDM simulation project can lead to signal elongation due to convolution results. So, by acknowledging this effect and implementing appropriate mitigation strategies, you can effectively address the challenges posed by fading channels and optimize the performance of your simulation.