Abstract
Cooperative communication for wireless networks has gained much attention because the spatial diversity can be achieved by nodes collaboration. However, to take full benefits of cooperative communications in practical networks, higher layer protocols, especially the medium access control (MAC) and network (NWK) layers should be designed carefully. A framework of cross-layer design for cooperative wireless networks, named CoopGeo, has been proposed in the literature. It is mainly composed of the forwarder and relay selections; the former is a joint MAC-NWK layer design and the latter is a joint MAC-PHY layer design. Nevertheless, to avoid the hidden node problem during the relay selection process, the choice of the relaying area in CoopGeo is based on the Reuleaux triangle graph, naturally leading to a loss of potential relays that are within the source’s transmission range. In this thesis, following the framework of CoopGeo, we propose a new MAC-PHY cross-layer design for relay selection, where the relaying area is modeled as an ellipse graph through a QoS-guaranteed coverage analysis. Specifically, every relay within the ellipse-shaped relaying area can provide a better cooperative link than the direct transmission. The use of the new relaying area, yet, leads to a hidden node problem and hence an increase of the collision probability during the relay selection contention process. We also propose a handshaking mechanism to solve this problem. Simulation results show that, in comparison with CoopGeo, the proposed relay selection scheme significantly improves the symbol error rate (SER) performance over fading channels. Moreover, our scheme also provides better performance in terms of the transmission error probability that is defined to assess the joint error behavior due to collision and channel fading.