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I'm working on a successive interference cancellation (SIC) project for an OFDM system.

I used pilots and least square channel estimation to estimate the channel frequency response (CFR.) It works just fine for recovering the QPSK data in the interference.

What I really want is to get the channel impulse response (CIR) of the interference channel so I can reconstruct the interference signal fully and then use it for SIC, so I took IFFT of the CFR in the hope that I will get CIR by doing so. That doesn't work at all.

I'm really new to this area, can anybody comment on if this is the right approach to estimate the CIR for a SIC application? If not, how should I approach this kind of problem?

Here's some information about the OFDM system:

  1. The channel has 5 taps.
  2. There are 240 subcarriers for the OFDM, and the IFFT length is 256.
  3. A cyclic prefix length of 18 is is used.

edit*

The channel estimation I used can recover the QPSK ok but I found that the estimated channel is quite different from the true one, especially the phase profile. Maybe I didn't do the channel estimation correctly?

From left to right: CFR, estimated CFR, recovered QPSK. This is the performance without noise.

From left to right: CFR, estimated CFR, recovered QPSK. This is the performance without noise

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Han Miao
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  • How do you determine "it doesn't work at all"? Because, if your CFR is good enough to recover the QPSK signal, then, well, it's a good estimate of the DFT of the CIR, by how I would define "good estimate". – Marcus Müller Mar 13 '22 at 12:06
  • Hi Marcus. Many thanks for the reply! I just edited the post! – Han Miao Mar 14 '22 at 17:21
  • thanks! How do you *measure* the difference between the estimated channel and the "true one"? Because to me these channels are almost identical – from the point of view of a system like yours. – Marcus Müller Mar 14 '22 at 17:23

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