Performance Analysis Of WLAN And Ad Hoc Network In The Interference Environment And Study Of Related Strategy

Modern communication requires high transmit rate, high mobility, wide converge and multiple services. The next generation mobile communication will integrate various types of wireless network technique such as WLAN, WPAN and MANET, and realize different traffic such as voice, multimedia and data on all-IP core network.WLAN and Ad hoc networks are widely applied in different fields,but the limited frequency bandwidth will induce the inter-system and intra-system interference , and reduce the performance of network. We analyze the performance of WLAN and Ad hoc network, and discuss the strategy of reducing interference.Firstly, we discuss interference mechanism of ISM frequency band, and analyze the performance of WLAN with interference from other equipments.We then simulate the BER(bit error rate) performance of WLAN by baseband model.We compare the different performance factor in interference environment by combining time-frequency collision analysis, and propose an adaptive packet adjustment scheme to improve the throughput performance of WLAN.Secondly, we study mechanisms to scale the capacity of hot-spots to a scenario with multiple WISPs(Wireless Internet Service Provider) and many wireless users. We first study the impact of separating each service provider at the physical layer using multiple overlapping channels as provided by the IEEE 802.11 standard. We model the effects of channel overlap for current systems and show that they have severe scaling limitations, study the impact of such factors as channel conditions, node density, channel allocation policies, and MAC protocol on throughput scaling and fairness.Base on the concept of Virtual Access Point, we propose a VAP structure with multiple (but limited) air interfaces shared by multi service provider.By using Multi-channel Opportunistic Auto Rate (M-OAR) protocol on VAP, it can increase throughput by exploiting temporal variations of multiple IEEE 802.11 channels to opportunistically select high quality channels.Finally, we analyze the interference performance in Ad hoc network and the feasibility of avoid interference by routing. A novel cross-layer routing technique was proposed for Ad Hoc networks with Multi-rate Mechanism based on analysis of network delay. Combining the SNR measure on physical layer with the delay estimate on MAC layer, we propose a routing metric, which allows us to select a route with...