Hi, I am working on equalization schemes without using Viterbi type of algorithms. Assume that complexity is not an issue. I am trying to detect the received samples using ML equation. Mathematically , if a1, a2, a3 .. aN are the input symbols, say h1, h2, h3 are the channel tap gains. Then the received signal is represented in vector fom as R= A*h+n, where R is the received vector of N samples, n is the AWGN vector, and A is the data matrix such that A*h implements the convolution operation between the data vector and the channel. Accoring to the ML criteria, I am checking the norm square of ( R-A*H), and assigning the ML data bit whch has the minimum norm. My problem starts when I am using a channel code with this scheme, as my channel code needs soft info, I m findding the LLR at the equalizer o/p which has minimum norm but with the oppoisite sign to the ML data bit found above. To my surprise, every time I am finding a code word same as ML except a chnage in the bit position for which I am deciding the LLR. I am unable to find the bug, is it happens like that ? I feel this thing will happen only when the chanel is a AWGN only. Any idea, where I am doing wrong? Thanks in advance, -SaiRamesh.

# ML equalizer

Started by ●November 6, 2006