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Coded Protocols for Implementing Cooperative Diversity June 30 2004 Matthew Valenti Assistant Professor West Virginia University Morgantown WV 26506 6109 mvalenti wvu edu Problem Statement Consider the following ad hoc network Source Destination Relays Questions How can the message be efficiently routed to the destination What is the tradeoff between latency and energy efficiency How to implement error control routing and access control Hybrid ARQ Both FEC and ARQ are permitted Joint cross layer solution is emphasized 6 30 2004 Coded Protocols for Cooperative Diversity 2 31 1 Conventional Approach Multihop Multihop picks from among several possible routes Source Destination Relays Drawbacks Routing tables need to be created and maintained Not robust to changes in topology interference or channel Routing ultimately relies on cascade of point point links Spatial MIMO diversity not exploited Wireless is broadcast oriented not link oriented The network could instead be interpreted as a large array 6 30 2004 3 31 Coded Protocols for Cooperative Diversity Conventional Antenna Arrays With a conventional array elements are closely spaced 2 and connected through high bandwidth cabling Microdiversity Receiver Transmitter 6 30 2004 Coded Protocols for Cooperative Diversity 4 31 2 Distributed Antenna Array With a distributed array the antennas are widely separated e g different base stations and connected through a moderate bandwidth backbone Macrodiversity Receiver 2 Transmitter Backbone Network Receiver 1 6 30 2004 Coded Protocols for Cooperative Diversity 5 31 Virtual Antenna Array With a virtual array the antenna elements are widely spaced attached to different receivers but are not connected by a backbone Virtual connection achieved by MAC layer design Decentralized macrodiversity Related to the relay channel and cooperative diversity Receiver 2 Transmitter Virtual Connection Receiver 1 6 30 2004 Coded Protocols for Cooperative Diversity 6 31 3 Related Work Several options



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