extension of the coverage region of multiple access channels by using a relay

From practical and theoretical viewpoints, performance analysis of communication systems by using information-theoretic results is important. in this paper, based on our previous work on multiple access channel (mac) and multiple access relay channel (marc), we analyze the impact of a relay on the fundamental wireless communications concept, i.e., coverage region of marc, as a basic model for uplink communications between a base station and users with the help of a relay. this analysis includes the coverage region for the mac as a special case. considering rate regions for the gaussian marc and fading gaussian marc, it is proved that in a fixed transmission rate, the relay extends coverage region of the marc. numerical illustrations confirm our theoretical results.