Research And Implementation Of MAC Protocol In Wireless Access Networks

Because of its flexibility and capability to supply network service "Anywhere, Anytime", Wireless access network (WAN) has an irreplaceable position in the compass of network accessing. The procedure of standardization of those WAN technologies is accelerated by the increasing demands of subscribers and the development of technology. At the same time, the standardization procedure in WPAN/WLAN/WMAN/WRAN by IEEE 802 committee is also accelerating the development of the product and market. Because wireless medium access control (MAC) protocol is the kernel technology of WAN, researching wireless MAC plays an important role in developing new WAN systems that are more efficient in resource usage, more reliable in performance and provides better quality of service (QoS).In this thesis, we first introduced some WAN system, and analyzed the important factors that have significant influence in designing WAN MAC protocol. And then we chose IEEE 802.11 protocol and IEEE 802.16 protocol, as representatives, to compare the distributed asynchronous accessing control with the concentrated synchronous accessing control in the aspects of frame formats, network accessing and QoS.In order to check the performance of MAC protocols in practical environments, we build a wireless accessing test platform. The platform has a piece of FPGA and an ARM processor in which we implement the MAC protocol. The physical layer in use is CC2500 radio frequency chip now, and also we set aside some ports for substitutions.In the last part of this paper, we explain in detail the way we implement an distributed MAC protocol in the platform based on IEEE 802.11 DCF. In the implemented protocol, new frame formats and the protocol processing module partition are designed. We describe the processing flow of every module in Specification and Description Language (SDL), and the meaning of every step in the processing flow, the interactive service primitives and respond of physical instrument are explained in detail for every processing flow. In the end, the inter-frame space (IFS) and Back-off slot are analyzed and measured because of their important influence to the performance of MAC protocol.