Çok-sekmeli telsiz ağlar için bir analitik IEEE 802.11 DCF modeli ve modelin ulaştırılan iş ile enerji analizine uygulanması

In this thesis, we present an analytical model for the IEEE 802.11 DCF in multi-hop networks that considers hidden terminals and works for a large range of traffic loads. A goodput model which considers rate reduction due to collisions, retransmissions and hidden terminals, and an energy model, which considers energy consumption due to collisions, retransmissions, exponential backoff and freezing mechanisms, and overhearing of nodes, are proposed and used to analyze the goodput and energy performance of various routing strategies in IEEE 802.11 DCF based wireless multi-hop networks. Moreover, an adaptive routing algorithm which determines the optimal routing strategy adaptively according to the network and traffic conditions is suggested.Viewed from goodput aspect the results are as follows: Under light traffic, arrival rate of packets is dominant, making any routing strategy equivalently optimal. Under moderate traffic, concurrent transmissions dominate and multi-hop transmissions become more advantageous. At heavy traffic, multi-hopping becomes unstable due to increased packet collisions and excessive traffic congestion, and direct transmission increases goodput. From a throughput aspect, it is shown that throughput is topology dependent rather than traffic load dependent, and multi-hopping is optimal for large networks whereas direct transmissions may increase the throughput for small networks.Viewed from energy aspect similar results are obtained: Under light traffic, energy spent during idle mode dominates in the energy model, making any routing strategy nearly optimal. Under moderate traffic, energy spent during idle and receive modes dominates and multi-hop transmissions become more advantageous as the optimal hop number varies with processing power consumed at relay nodes. At the very heavy traffic conditions, multi-hopping becomes unstable due to increased collisions and direct transmission becomes more energy-efficient.The choice of hop-count in routing strategy is observed to affect energy-efficiency and goodput more for large and homogeneous networks where it is possible to use shorter hops each covering similar distances. The results indicate that a cross-layered routing approach, which takes energy expenditure due to MAC contentions into account and dynamically changes therouting strategy according to the network traffic load, can increase goodput by at least %18 and save energy by at least 21% in a realistic wireless network where the network traffic load changes in time. The goodput gain increases up to 222% and energy saving up to 68% for denser networks where multi-hopping with much shorter hops becomes possible.