I don't have a lot of background on wireless communication but as far as I understand, applying IFFT on Channel Frequency Response (CFR) would transform the data into time domain Channel Impulse Response (CIR), in which it shows the delay spread of the different multiple paths.
The CSI measuring tool I'm using measures 30 subcarriers resulting in 30 complex number CFRs per a single CSI trace. So when I apply 30-point IFFT on the CFR, the output is a CIR with 30 time-domain values.
My question is,
- What is the time unit of the converted CIR?
- How much seconds are they (the 30 impulse responses) apart?
- Also, are the impulses like the echoes of the transmitted signal?
- The number of multi-path is not determined. So I assume that an impulse response does not represent a single path, since the number of impulse response is fixed to 30. Then how should I understand the CIR value with respect to the multi-paths?