MMSE based Equalization in OFDM systems

[danM]

Hi,

What is the performance difference of MMSE equalizer and ZF equalizer in a
OFDM system. I have simulation 3 tap Rayleigh channel for QPSK ODFM system
and found out that both the equalizers give the same performance.

But in Single carrier Frequency Domain Equalization, MMSE performs
significantly better than ZF.

I modeled the equalizers for OFDM as follows.
e.g. Sub carrier = i

Y = H . X + V (in frequency domain)

H is the flat fading channel for the ith sub carrier, X is the transmitted
symbol and V is the noise sample. N0 is the noise variance.

When I equalize this signal in frequency domain,

My ZF equalizer: Q = 1/H
MMSE equalizer: Q = H*/ (H.H* + N0)

The output results are attached in the PNG file. For OFDM, both ZF and MMSE equalizers are overlapped.

Can anyone please advice me in this regard.

Thanks in advance.