| In a wireless network that employs cooperative communication, through cooperation among the spatially dispersed single-antenna terminals, some significant benefits of multiple-antenna systems can be achieved, such as diversity gain. Based on a large body of research work, it has been demonstrated that exploiting cooperative diversity can offer significant potential advantages in terms of transmission range, capacity, and quality. However, for most of the existing works on cooperative communication, the focus is on optimizing quality of service (QoS) by exploiting central control and/or full availability of channel state information (CSI) at the transmitter(s). In this way, the required overhead, which might be significant, is usually ignored this is an important reason for the considerable gap between theory and practice. Little attention, however, has been paid to designing efficient decentralized cooperative strategies that can achieve a good tradeoff between QoS and overhead in realistic scenarios. In this work, we concentrate on decentralized cooperation with an emphasis on systems that work well with minimal amounts of network control, limited availability of CSI at the transmitter(s), and acceptable processing complexity. In particular, with a focus on decentralized distributed space-time block coding (Dis-STBC) techniques and mean-CSI-based Best-Select cooperation in selective decode-and-forward relaying networks, the research is carried out for single- and multiple-source scenarios, two-stage and multihop networks, as well as energy-constrained networks. Moreover, for all the decentralized cooperative strategies proposed in this work, practical implementation issues are also considered.First, decentralized Dis-STBC techniques are investigated. We analyze the diversity benefit and evaluate the outage performance for several decentralized Dis-STBC schemes including pre-assign, m-group, and continuous randomized schemes. Then, focusing on discrete randomized Dis-STBC, a closed-form outage expression is derived and some rules for optimizing this scheme are provided. Based on assuming the candidate relays know only the local mean CSI, a power-efficient relay-selection strategy is also designed for either two-stage or multihop cooperative networks using decentralized Dis-STBC. Later, two ad-hoc, yet efficient, power allocation strategies are proposed for decentralized Dis-STBC system where knowledge about the CSI is not available at the transmitter(s). Further, when there are multiple sources which have a common destination, we present a practical strategy to apply decentralized Dis-STBC to this scenario.We also study mean-CSI-based Best-Select cooperation. For a multihop network where mean-CSI-based Best-Select cooperation is employed at each relaying hop, a hop-by-hop routing strategy is designed to optimize the end-to-end out-age performance. Then, when there are multiple source-destination pairs and the mean-CSI-based Best-Select strategy is used to perform relay selection, a cooperative network coding scheme is proposed to achieve full-rate re-transmission for each single source-destination pair. We also consider lifetime maximization for an energy-constrained network using mean-CSI-based Best-Select cooperation. |
