Effects of relay and side information at one encoder on the coverage regions in Gaussian multiple-access channel

The two-user multiple-access relay channel (MARC) is investigated in the presence of side information (SI) available only at the informed transmitter in the present article. First, for the discrete alphabet and memoryless MARC with common and private messages, partial decode and forward strategy at the relay and fixed locations of the nodes, a general achievable rate region is obtained. The SI effect is seen and can be analyzed. Second, we extend the discrete result to a practical communications model: Gaussian multiple-access relay channel (GMARC), showing previous works as its special cases. Third, the effect of (perfect and nonperfect) SI on the maximum coverage region of GMARC for a fixed rate of the transmitters and a fixed distance between relay and destination is analyzed. It is shown that the SI increases the coverage region of encoders, and consequently, it can improve communication energy efficiency. Finally, mathematical findings are validated numerically by using Matlab.