I am simulating an OFDM system and want to employ concatenated codes with different modulation schemes. I have a few queries about it. 1. RS code works on frame-by-frame basis like for a shortened code RS(32,24) on byte boundary. In this case, I need a minimum of 24*8 uncoded data bits. If i work on this boundary, the resulting symbols dont map completely to the OFDM symbol. How can i make it satisfy both the requirements i.e. RS frame boundary as well as no. of OFDM data carriers. (It maps directly for some modulation schemes and not the all) 2. Whenever I simulate the system using Matlab rayleighchan command, either i get .5 ber or 0. I want to evaluate the performance of the concatenated codes but cannot see it working. 3. What is the design criteria for interleaver depth design for concatenated codes. All i know is the criteria for individual RS or CC codes but not for the concatenated ones. My guess in this case is since data is convolutinoaly coded after RS encoder, the interleaver should be designed w.r.t. the traceback length of the viterbi decoder. Best Regards, Ubaid
Question regarding Concatenated Codes on OFDM
Started by ●June 30, 2008