Improved Ad Hoc Networks Based On The Csma / Ca Mac Protocol Design

An Ad Hoc network is a wireless multi-hop network with self-configuration and self-adaptation, which consists of a cluster of mobile stations without a fixed network infrastructure. Because of its characteristics of flexibility in networking, capability of forwarding packets over multi-hop and completely distributed operations, Ad Hoc net- work is hardly restricted by environments, and its robustness is also very strong. As a result, Ad Hoc network is especially fit for applications such as tactical communication for military, search and rescue mission, disaster recovery, etc.Since the wireless medium is a broadcast medium shared by all stations, a medium access control (MAC) protocol is needed to define rules that allow stations to access the medium in collision-less, efficient and fair manner. Therefore, MAC protocol is a key issue that determines the performance of network.First, we make classification, evaluation and summary of MAC protocols for Ad Hoc network, including contention-based MAC protocols, schedule-based MAC proto- cols and QoS MAC protocols. Second, under the single channel contention-based medium access control mode, aiming at solving the hidden terminal, exposed terminal problems and QoS problems respectively, we propose two MAC protocols: CSMA/CA improved mechanism based on fragmentation and EDCF-RD protocol. The former adopts fragmentation technology to provide more opportunities for parallel transmission. Therefore, it can alleviate hidden terminal and exposed terminal problems and increase the spatial reuse ratio of radio channel, so as to improve network performance. The later extends one time RTS/CTS handshake to three times, adopts receiver-driven method, allows stations of high priority applications to snatch channel resources from stations of low priority applications, in order to guarantee the QoS requirements for high priority applications.In this paper, Chapter 1 briefly introduces the characteristics of Ad Hoc network and its MAC protocols. Chapter 2 makes particular introduction and analysis of various MAC protocols for Ad Hoc network. Chapter 3 focuses on CSMA/CA improved mechanism based on fragmentation. Chapter 4 introduces the EDCF-RD protocol. Chapter 5 discusses the method of building a simulation model. Chapter 6 analyses the performance of the two MAC protocols. Finally, Chapter 7 summarizes the work and proposes the improvements.