Research On Medium Access Control And Radio Resource Management In Wireless Ad Hoc Networks

Wireless Ad Hoc network does not depend on any fixed support infrastructure and has the advantages of deployability, flexibility, robustness, etc. The requirements on information share and data exchange among wireless smart devices and consumer electronics promote greatly the research on wireless Ad Hoc networks. This thesis focuses on the wireless medium access control (MAC) and the radio resource management schemes in the WLAN- and WPAN-based Ad Hoc networks.As a distributed contention protocol, IEEE 802.11 MAC DCF (Distributed Coordination Function) is adopted mostly in wireless Ad Hoc network test-beds and simulations. To deal with the local congestion problem and decrease the end-to-end delay in packet transferring, the FPF scheme and MFCBI scheme are proposed. The former is based on adaptive backoff contention window and the latter replaces the four-way handshaking process with a three-way one by utilizing the broadcast characteristic of radio propagation. Simulation results show that the proposed schemes can effectively improve the network performance, mitigate the local congestion to a great extent, improve the network throughput and reduce the average end-to-end delay.Secondly, the medium access control scheme is studied in WPAN Ad Hoc networks. To deal with the insufficiency in scalability for wireless Ad Hoc networks with locally centralized control, a communication scheme among multiple piconets, i.e. USF-DSTD scheme, is proposed. This scheme is based on the IEEE 802.15.3 high-rate WPAN MAC protocol. The analysis and the simulations show that, by choosing appropriate parameters, the USF-DSTD scheme can provide QoS guarantee for real-time services, such as voice, video and audio. This work forms the basis of QoS support and efficient radio resource management in WPAN Ad Hoc networks.Thirdly, the call admission control issue for multiple adaptive services is addressed. According to the characteristic of adaptive services, three functions, i.e. bandwidth satisfaction function, revenue rate function and bandwidth reallocation cost function, are proposed first. Based on the three functions, a reservation-based and revenue test with optimal bandwidth reallocation (Rev-RT-OBA) CAC scheme is proposed which is simple and efficient. Both the analysis and the simulation results show that, under almost the same bandwidth utilization ratio, the Rev-RT-OBA CAC scheme solves the unfairness problem in admitting multiple classes of services with different bandwidth requirements. At the same time, the required admission priority level can be guaranteed for various classes of services. Afterwards, the SMDP-based optimal call admission control problem is further studied. The SMDP-OBA CAC scheme is proposed and compared with the Rev-RT-OBA CAC scheme. The results show that, with an appropriate tradeoff in call blocking probability between traffic classes, the performances measured by the expected revenue rate and the expected bandwidth utilization rate are greatly improved. At the same time, the minimum QoS (orbandwidth) requirement of every call can be guaranteed.Finally, it computes the capacity region for the WPAN Ad Hoc networks. The system model is proposed and the capacity region is defined firstly. Then the computing approach for the capacity region is formulated. The impacts of transmission power, discrete power control, discrete transmission rate and multihop routing on the capacity region are studied. These provide important theoretical guidelines for the design of cross-piconet communication, routing protocol and power control algorithm in wireless piconet-based Ad Hoc networks.