A New LDPC Coded Scheme for Two-User Gaussian Multiple Access Channels

We propose a new low-density parity-check coded scheme for two-user Gaussian multiple access channels (GMACs) with equal rate and equal average power constraints. In the proposed scheme, we divide a code word into two parts with equal length and transmit them by using BPSK signals with two power levels. Two users use the two power levels alternatively to avoid ambiguity problem in two-user GMACs. We optimize the ratio between the two power levels to minimize the required average signal-to-noise ratio for a given rate. We also design a joint decoding algorithm for our proposed scheme. Numerical results show that the proposed scheme has a better bit error rate performance, compared with the existing schemes.