Cooperative transmission among ordinary users in wireless communication networks

The objective of this paper is to determine the conditions under which two ordinary users in a communication network having information bound for the same receiver can benefit by relaying portions of each others data. Each user is allocated the same bandwidth, and the objective of each user is to maximize information transfer per joule. The users are free to either use their entire allocated bandwidth to transfer their own messages or to allocate portions of their bandwidth to cooperatively transfer messages with another user. In the non-cooperative mode, the users maximize return by adjusting power whereas in the cooperative mode, the users vary both their transmission powers and the proportion of hared bandwidth to achieve maximal utility. Solution techniques are developed for the case of cooperating users in symmetric user-position and channel condition setups. Within this setup, there are two options, one where each user gets the same return (symmetric), and one in which the two users may achieve different returns (asymmetric). We find that gains are possible with both options and that the asymmetric option yields larger returns but requires scheduling in order to achieve equal throughput.