The challenges involved in the design of efficient communication systems for the wireless medium can be attributed to the fact that the wireless medium possesses certain unique characteristics, the most important ones being the broadcast nature of the wireless medium, the susceptibility to interference effects, and the effects of path loss and fading on wireless link quality. Cooperation between different transceivers can potentially aid further development of next-generation wireless communication systems that demand high data rates and an excellent quality of service (QoS). This is possible by exploiting the broadcast nature of the wireless medium, and the diversity advantages that a multi-user system offers.

We first consider a general single-source-single-destination wireless relay network and propose an information flow-optimized cooperative transmission design that achieves the optimal diversity-multiplexing tradeoff. Next, we apply game-theoretic techniques to the problems of resource allocation and characterization of cooperative behavior in a two-user fading multiple-access channel (MAC), with uncertainty about the channel state information at the transmitters (CSIT).

In the third part of the dissertation, a more active form the above cooperative behavior is studied via a two-user fading cooperative multiple-access channel (CMAC), where each user, along with transmitting its own information to the destination, helps the other by forwarding the latter's information. We propose efficient cooperative transmission strategies based on a flow-theoretic approach, and evaluate their performances using numerical simulations.

Finally, we consider communication through a two-user interference channel with unidirectional cooperation (ICUC), wherein one source uses its knowledge of the message of the other to reduce the interference to its own transmission, and simultaneously, help the other user-pair via cooperative relaying. We consider a very realistic scenario in which the cooperating source is subjected to a causality constraint. We derive a new achievable rate region for the discrete memoryless version of this form of ICUC, and demonstrate the contributions of the various coding strategies involved via numerical simulations for Gaussian channels. We also study the same channel with the cooperating source being subject to the half-duplex constraint as well. A discrete memoryless channel model incorporating the half-duplex constraint is presented, and a new achievable rate region, that enlarges the largest known rate region for the Gaussian version of this channel, is derived for this channel. The achievable rate region for the proposed coding scheme, specialized for Gaussian channels, is numerically evaluated and the strict inclusion of the previously known largest rate region is demonstrated.