Cooperative Communications with Network Coding for Wireless Uplink Channels

Future wireless systems are characterized by large user capacity, high speed, high reliability. Yet, inherent fading and interference of wireless communications render these design objectives challenging. As an efficient and inexpensive method to combat wireless fading, cooperative communications ([1], [2]) has recently attracted lots of research efforts and practical implementations. The principle of cooperative communications is illustrated in Figure 1. In wireless uplinks, two or more users sending messages to a common base station (BS) form partners to help each other on information transmission. When user 1 communicates to the BS, the relay (partner user 2) also receives the messages for the broadcasting property of the wireless medium. Therefore, the information messages from user 1 are transmitted to the BS through two fading paths: one direct path and one indirect path through relay (user 2). The potential gain provided by the relay includes coverage, cooperative diversity, and increased spectral efficiency [1], [2]. Compared to the traditional MIMO, cooperative communications are not subject to the limitations of antenna size, cost, hardware etc.