Coded cooperation: Partner choice and rate adaptation

Cooperative communication enables multiple nodes in a wireless network work together to form a virtual antenna array. The destination receives multiple versions of the same message from the source and one or more relays, and combines these to create diversity.; In this dissertation, we first consider a coded cooperative system under quasi-static Rayleigh fading and investigate the partner choice problem. We find conditions on the inter-user and user-to-destination channel qualities for cooperation to be beneficial. Using frame error rate as a metric, we define the user cooperation gain (G) for evaluating the relative performance improvement of cooperative over direct transmission when a particular channel code is used. We introduce the cooperation decision parameter (CDP) which is a function of user-to-destination average received signal to noise ratios and demonstrate that whether cooperation is useful or not (G > 1 or G < 1) depends only on the CDP, not the inter-user link quality. We propose to use an analytical formulation of the CDP to investigate user cooperation gain and provide insights on how a user can choose among possible partners to maximize cooperation gain. All of our theoretical results are verified through numerical examples. Our results enable online cooperative partner assignments without the need of large look-up tables or extensive simulations.; Next we propose adaptive modulation and coding for a cooperative relaying system with the goal of maximizing the data throughput. We derive the throughput expressions of stationary and dynamic coded cooperation. We find, through a realistic simulation scenario for IEEE 802.11 WLAN, that rate adaptive cooperation provides much higher throughput than multihop and direct transmission; however unlike direct transmission and multihop, a system wide optimization is necessary to maximize the throughput in coded cooperation. Finally, we briefly describe how MAC algorithms exploiting physical layer cooperation and rate adaptation can boost the throughput over legacy 802.11g system.