In recent years, there has been an upsurge of interest in relay-based wireless networks in both industry and academia. With the introduction of relay node, which can forward packet for some other nodes which require relaying assistance, the network performance can be dramatically improved: the coverage of an infrastructure network is extended; spatial diversity is exploited and system capacity is increased; meanwhile, the transmission reliability is enhanced. In relay wireless networks, in order to fully exploit the benefit of relay transmissions, MAC and network layer schemes need to be redesigned. In this thesis, we will focus on the study of relay selection problem in MAC layer and optimal routing decision problem in network layer. Several relay and routing selection schemes are prop...[ Read more ]

In recent years, there has been an upsurge of interest in relay-based wireless networks in both industry and academia. With the introduction of relay node, which can forward packet for some other nodes which require relaying assistance, the network performance can be dramatically improved: the coverage of an infrastructure network is extended; spatial diversity is exploited and system capacity is increased; meanwhile, the transmission reliability is enhanced. In relay wireless networks, in order to fully exploit the benefit of relay transmissions, MAC and network layer schemes need to be redesigned. In this thesis, we will focus on the study of relay selection problem in MAC layer and optimal routing decision problem in network layer. Several relay and routing selection schemes are proposed for different wireless applications when concept of relaying is applied. In relay selection part, a cooperative MAC protocol is designed to dynamically select relay nodes according to real-time channel condition and contention relationship for broadcast traffics in vehicular networks; in respect to the cognitive radio networks, a relay-based cognitive radio architecture is proposed to balance the spectrum availability and traffic demand for secondary users, an experimental testbed is constructed to verify its effectiveness; we also propose an incentive relay set selection scheme to motivate secondary users to act as cooperative relays to forward packets for primary users. In routing selection part, a cooperative routing scheme which considers contention relationship among links is proposed in multi-source multi-destination multi-hop wireless networks; a cooperative network coding-aware routing scheme is given to enable relaying to further enhance the benefit of network coding in wireless networks. Finally, a software-defined radio-based cooperative communication testbed is built to evaluate the performance of various cooperative transmission schemes. The above studies demonstrate that with appropriate relay and routing schemes, relaying benefit and cooperative diversity is fully exploited and network performance is remarkably enhanced in relay-based wireless networks.