Research On MAC Protocol And Routing Algorithms In Wireless Self-organizing Networks

Wireless self-organizing network, which consist of a group of mobile nodes equipped with transceivers, is a dynamic reconstructable multi-hop network without the support of fixed infrastructures and has some characteristics such as distributed, self-organizing, self-configuring, self-managing, and so on. Wireless self-organizing network can afford a communication platform if the existing networking infrastructure can't be used. It expands the using of mobile communication networks and can be used widely in tactical communication, emergency search-and-rescue operations, meetings or conventions. Wireless self-organizing network is an important component of the next generation network (NGN). The dissertation mainly does research on the following content: the MAC protocol of wireless self-organizing network that can switch the work manner adaptively, the improvement of back-off algorithm of MAC protocol, the path stability based on-demand single-path routing, the lifetime and flow dispatch based multipath routing, and the geographic location information based routing.Based on the time duration of single successful packet transmission, the time duration of single failing packet transmission and the current collision probability of channel, the formulas of the optimal RTS threshold are given out, which aim to minimize the time overhead of packet transmission. The optimal RTS threshold is calculated by estimate the current collision probability P_c of channel. An adaptive RTS threshold adjustment algorithm is presented based on the calculating method of the optimal RTS threshold. Simulations validated the correctness of the adaptive RTS threshold adjustment algorithm. From the aspects of the time overhead of MAC frames and the transmission efficiency of 802.11 DCF, the performance of adaptive RTS threshold adjustment algorithm is better than that of the RTS access mode and the basic access mode, and it adapts to saturation state and non-saturation state. So the adaptive RTS threshold adjustment algorithm presented can effectively optimize the performance of IEEE 802.11 DCF.A DCF algorithm based on dynamic threshold, named DDCF (Dynamic threshold based DCF), has been presented. The theoretic basis of algorithm was given out and the theoretic model was established. The algorithm was simulated and the performance of DDCF, DCF, BDCF, and GDCF are compared. By theoretic analysis and simulations, it shows that because DDCF make the static value of contention window of nodes near the ideal value, so it promoted the overall system performance. DDCF can be realized base on DCF by suitable selected threshold serial G(i) without big modification. Compared with GDCF, DCF has the adaptive adjust ability according to the number of contention nodes.An on-demand routing protocol, named THP-AORP (Time-t Path Holding Probability Based Ad-hoc On-demand Routing Protocol), based on the analysis of the time-t holding probability of single link (P_m,n(d(m,n),t)), has been presented based on the time-t holding probability of a whole path (Ψ_S,D(t)). New protocol chooses the path that has the maximal time-t holding probability (Ψ_S,D(t)) as the best routing. Simulations show that, compared with AODV and DSR, new protocol saved the overhead of protocol, and reduced the end-to-end delay of packet.A multipath routing algorithm, named LFD-MR (Lifetime and Flow Dispatch based Multipath Routing), is presented. Compared with traditional MSR, being used long lifetime path and congested degree based multipath flow dispatch method, LFD-MR can decrease the average end-to-end delay of packet, promote the network throughput, increase the successful packet rate, and decrease the routing overhead.A novel location management scheme named SM-DHLM (Sub-zone Moving Distributed Hierarchical Location Management Scheme) has been proposed, Through distributed hierarchy and sub-zone moving, SM-DHLM decreases the probability of the nodes crossing the boundary of sub-zones, limits the location update messages into smaller sub-zones, decreases the overhead of location management, promotes the scalability of networks. Compared with the fixed Hierarchical Location Management Scheme, SM-DHLM has similar query success rate, has similar successful packet rate, has lower protocol overhead, and has lower average end-to-end delay.Finally, chapter 7 summarizes the dissertation, reviews the above research work and presents the future research directions.