Key Technologies In The Physical Layer And MAC Layer Applied On WLAN-Over-Fiber System

With the full coverage of today's WiFi hot spots and 3G mobile networks showering the city buildings, the two wireless technologies complement each other and promote the upgrade of the entire wireless services.However, along with the development of broadband access services,such as video on demand, interactive media, video surveillance, High Definition Television (HDTV),etc, bandwidth is still the bottleneck of the development of wireless communication technologies.At the same time, fiber has gradually penetrated from the core network to the user's access network. Passive optical network (PON) technology instead of copper-based wireline access technology has become the representative technology of the broadband optical access networks.The combination of flexible wireless and broadband wireline communication technologies will provide users with ubiquitous broadband access, as the future of communication's development. In this paper, the physical and MAC layers'technologies of WLAN over fiber system based on ROF integration technology have been studied. The main work of this paper is as follows:A WLAN over fiber system carrying multiple indoor broadband wireless access services (including 2G,3G and WiFi) is designed and simulated. The system performance and simulation results are analyzed, including the source signal modulation format, optical signal modulation and the fiber link dispersion nonlinear analysis, laser and detector performance analysis. In the end, the combination of DFB laser and MZM modulator is selected as the optimal solution to the single-sideband modulation or carrier-suppressed modulation modes,which can overcome dispersion and crosstalk effect over long distance.The introduction of WLAN over fiber system not only expands the system coverage, increases the number of mobile access users, but also increases the system load and end to end transmission delay. OPNET simulation platform is used for the MAC layer simulation, and the throughput, packet loss rate and delay parameters under DCF, RTS/CTS and PCF protocols are compared. Considering the convergence of WLAN over fiber system and PON access network, PCF protocol is proved to be the most suitable transmission mechanism in the MAC layer.