I am curious about the relationship between the number of transmitted pilot symbols in ISAC and the amplitude of the received signal.

I am currently running the example 'Integrated Sensing and Communication II: Communication-Centric Approach Using MIMO-OFDM'. In subframe B, I’m experimenting with increasing the spacing between pilot symbols to reduce the number of transmitted pilot symbols. However, I’ve noticed that the amplitude of the received signal gradually decreases. Could you explain why this is happening? Although the code performs interpolation between subcarriers, I’m curious why the reduction in the number of pilot symbols leads to a decrease in the amplitude of the received signal. The bit error rate also increases — can you explain why that happens?

Answer 1

[Akash Gopisetty]

When you increase the spacing between pilot symbols in OFDM, the receiver has fewer reference points to estimate the channel response. Although interpolation is used, if the channel varies between pilots, the estimation becomes less accurate. This can lead to underestimating the channel’s effect, which reduces the amplitude of the equalized received signal and increases the bit error rate.

Essentially, sparser pilots make channel estimation less reliable, especially in frequency-selective channels, which would explain both the amplitude drop and higher BER you observed.

[JG]

Thanks for your help.