Introduction

Wireless cellular networks have to be designed and deployed with unavoidable constraints on the limited radio resources such as bandwidth and transmit power. With the boom in the number of new users and the introduction of new wireless cellular services that require a large bandwidth or data rate, the demand for these resources, however, is rising exponentially. Finding a solution to meet this increasing demand with the available resources is a challenging research problem. The primary objective of such research is to find solutions that can improve the capacity and utilization of the radio resources that are available to the service providers. Based on the concept of relay channels, cooperative communication has been found to greatly enhance the performance of a resource-constrained wireless network. It can achieve benefits similar to those of the multipleinput multiple-output (MIMO) system without the need for multiple antennas at each node. By allowing users to cooperate and relay each other's messages to the destination, cooperative communication also improves the transmission quality. Because of the limited power and bandwidth resources of the cellular networks and the multipath fading nature of the wireless channels, the idea of cooperation is particularly attractive for wireless cellular networks.

Proposed cooperative schemes or strategies, such as decode-and-forward (DF), amplify-and-forward (AF), and coded cooperation, usually involve two steps of operation.