Study On Design Of Cooperative Diversity Protocols

It is well accepted that spatial, or multiple-antenna, diversity is an efficient technique to combat the negative effects of channel fading in wireless networks. However, the use of antenna arrays is not practical for deployment in some practical scenarios due to size and power limitations. Cooperative diversity is a novel transmission paradigm which has been recently introduced to overcome these limitations by pooling together the resources of neighboring nodes. This technique exploits the broadcast nature of wireless transmission and creates a virtual (distributed) antenna array through cooperating nodes to realize spatial diversity advantages.The major efforts of this dissertation are focused on design of cooperative diversity protocols. Specifically, three kinds of cooperation protocols are outlined, including basic cooperation strategies, space-time-coded cooperation protocols and coded cooperation. Basic cooperation strategies refer to fixed relaying schemes such as amplify-and-forward and decode-and-forward, selection relaying schemes that adapt based upon channel measurements between the cooperating terminals, and incremental relaying schemes that adapt based upon limited feedback from the destination terminal. In space-time-coded cooperation protocols, the space-time coding idea is extended to cooperative diversity. In this case, if the information of one source is located through more nodes, these nodes can utilize a space-time code to cooperatively transmit to the destination. Coded cooperation is a mechanism where cooperation is combined with channel coding. The basic idea is that each user, instead of repeating the received bits (either via amplification or decoding), tries to transmit incremental redundancy for its partner. Besides providing an overview of present cooperation protocols, this dissertation also develops several improved cooperation strategies. Compared with existing protocols, improved ones enjoy better performance in terms of spectral efficiency or transmission reliability, respectively. Throughout the thesis, information-theoretic outage probability is employed to characterize performance of various protocols.