Realistic Evaluation of Cooperative Relaying Networks Using Decentralized Distributed Space-Time Block Coding

Information theoretic studies have shown the significant performance improvements of cooperative communications. However, these studies ignore both the overheads incurred in real implementations of the cooperative techniques at the physical layer and their interactions with higher layer protocols in a networking context. In this paper, we study the performance of realistic networking scenarios facilitated by cooperation by taking overheads incurred at the physical, MAC, and network layers into account. In particular, (1) we modify the physical layer model of the QualNet network simulator to incorporate decentralized distributed space-time block coding into all SINR calculations and to combine signals transmitted concurrently from multiple relays, (2) we implement a path-centric MAC protocol to both reserve a multihop path between source and destination nodes and coordination relay nodes, and (3) we modify the DSR protocol to support path reservation at the network layer. Preliminary simulation results demonstrate that significant performance improvement can be achieved by employing cooperation. We also demonstrate the overheads which challenge their effectiveness in real networks.