Relay Selection And Cooperative Routing Algorithms Based On Energy-constrained Wireless Networks

Cooperative communication, as a newly-developed technology in recent years,by making use of the potential resource of the broadcast of wireless channel,realizes distributed transmitting and information processing by the cooperating ofnodes in the network. Cooperative communication can improve communicationcapacity, rate and performance. It also has a great advantage in prolonging networklifetime, improving network throughput and extending transmission coverage. Animportant issue in the process of cooperative communication is that how to choosean appropriate relay node to participate in cooperative transmission with multiplerelay nodes in the network. In addition, combining cooperative communication androuting selection to play the advantage of cooperative communication in thenetwork layer also receives widespread attention.This thesis first proposes an energy-efficient BRBT relay selection algorithm.In most previous articles, the relay doesn’t have the buffering capacity. Thisalgorithm exceeds this limit and enables the relay with buffer, so can make therelays for receiving and transmitting to be different. By taking into accountinstantaneous channel state information, remaining energy and the queuing states,we select the best relay for data receiving and the best relay for data transmittingrespectively through different weighting functions. Furthermore, the powerallocation between the source node and the relay node is considered to reduce thepacket loss rate caused by the difference of channel rate between source node torelay node and relay node to destination. Simulation results show that thisalgorithm prolongs the network lifetime efficiently and improves networkthroughput significantly as the number of relays increases and reduces the packetloss rate after considering the power allocation.For jointly combining advantages of cooperative communication at thephysical layer and distributed routing schemes at the network layer, furthermorethis thesis proposes a maximizing lifetime location-based routing algorithm(MLLBCR). In this algorithm, the outage probabilities of direct link andcooperative link were first analyzed, and then the optimal power allocationmechanism is analyzed for these two kinds of link, given the outage probability ofthe link constrained at a certain target level. Subsequently, link costs including the transmitting energy and the circuit processing energy are constructed. At last, wechoose the candidate relays by area forwarding mechanism and give the MLLBCRalgorithm implementation steps. Simulation results prove the algorithm’s efficiencyin reducing the transmission power and prolonging the network lifetime.