Abstract:

A study on approach multiple access channel capacity by means of power allocation and low density parity check (LDPC) codes optimization is presented. The power allocation scheme is designed based on the maximization of mutual information and then the power profile is obtained. The probability density function of message on factor graph is obtained by Gaussian approximation. The optimized LDPC code degree profiles are obtained by using the power profile. Iterative detection and decoding algorithm is also applied to combat multiple access interference. Simulation showes that the bit error probability performance can be improved by 16dB at 10-5 with the proposed method compared with that of only optimization of LDPC code.

Key words: multiple access channel, low density parity check codes, Gaussian approximation, interleaver division multiple access, power allocation, code optimization