Distributed Closed-Loop Quasi-Orthogonal Space Time Block Coding with four relay Nodes: overcoming Imperfect Synchronization
DOI: 10.1109/WiMob.2009.61 Conference: 5th IEEE International Conference on Wireless and Mobile Computing, Networking and Communications, WiMob 2009, Marrakech, Morocco, 12-14 October 2009, Proceedings
In this paper, closed-loop quasi-orthogonal space time block coding(QO-STBC) is exploited within a four relay node transmission scheme to achieve full-rate and increase the available diversity gain provided by earlier two relay approaches. The problem of imperfect synchronization between relay nodes is overcome by applying a parallel interference cancellation (PIC) detection scheme at thedestination node. Bit error rate simulations confirm the advantages of the proposed methodology for a range of levels of imperfect synchronization and that only a small number of iterations is necessary within the PIC detection.
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ABSTRACT: In this paper, we select the best two relays from a set of available relays, each of which is equipped with two antennas, based on the instantaneous path gains. Closed-loop quasi orthogonal space time block coding is then applied over the selected two relays to maximize cooperative diversity. parallel interference cancellation detection is also applied at the destination node to mitigate the problem of imperfect synchronization between the relay nodes. End-to-end bit error rate simulations confirm that the selection scheme yields a significant improvement in performance over the conventional scheme without using relay selection. Furthermore, the bit error rate simulations confirm the advantages of the detection scheme for a range of levels of asynchronism, and that only a small number of iterations is required in the parallel interference cancellation technique.
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ABSTRACT: Deployment of Space-Time Block Code (STBC) over wireless relaying communication networks has been identified as one of the most promising techniques because of its potential to support high-performance and high data-rate for wireless communication technologies of the future. It is called Distributed-STBC (D-STBC) as it uses clients’ nodes as relaying nodes to form a virtual Multiple-Input Multiple-Output (MIMO) channel. However, this requires perfect synchronization among the relaying nodes. Unfortunately, as this is impossible to achieve in real world networks, the structure of the code matrix is compromised causing the channel to appear dispersive. This paper firstly derives a general model of D-STBC systems which will then be used to show the effects of imperfect synchronization on such schemes. Then, it highlights the majority of the schemes used to mitigate the performance degradation due to the asynchronism. In addition, it suggests some schemes that could be considered when conditions of imperfect synchronization exist.
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