Study On Media Access Control And Authentication Protocols In IEEE 802.11 Wireless Networks

In recent years,with the tremedous development in wireless communication technology, the IEEE 802.11 wireless network has been widely applied. At the same time,the performance and the security of wireless network is becoming the focus. Medium Access Control (MAC) scheme is the key factor of the wireless network efficiency, and access authentication protocols are the basis of the wireless network security. So it is significant to study the medium access control and the authentication protocol in the IEEE 802.11 wireless network. The main results are as following:1. A performance analysis model based on packet arrival rate is proposed for IEEE 802.11 DCF in infrastructure-based WLAN. A three dimensional discrete time Markov chain is used to model the node, and normalized throughout, packet delay and packet losing ratio are obtained. The Model not only takes into account the factors of number of terminals, traffic loads, the binary exponential back-off mechanism, but analyzes the impact of the finite queue system at the MAC layer.To maximize the non-saturation throughput, the optimum formula of minimum contention window and packet length under finite load were derived. Simulation results show that the proposed model can predict validly the performance of the DCF under various packet arrival rates and optimal methods can enhance system performance.2. According to the requirements of real-time multimedia services in Wireless LANs, a fast secure handoff scheme based on mobility prediction is proposed. By using the stations'mobility patterns and handoff location, a station is only scanned with unicast channels selected by neighbor graphs, which reduces the scanning delay. Furthermore, Pairwise transient key is computed in advance and message integrity code is piggybacked in probing massages, which satisfies desirable security attributes and reduces the re-authentication delay. Simulation results show that the proposed method reduces the handoff delays obviously.3. WLAN mesh is a new networking technology, but the handoff of mesh points (MPs) can not be supported by the current standard of WLAN mesh. So a complete secuirity solution of WLAN mesh is proposed, which consists of a three-party(Mesh Point, Mesh Key Distributor and Authentication Server) authentication protocol for the access of a MP to the wireless network and an authentication protocol for the fast handoff of a MP. The four-way hand handshake is not required in the new protocols. Finally, we show that the new protocol is provably secure under DDH assumption and has a much better performance than the current solution.4. Security of 3G-WLAN interworking networks is a focus problem. Since several shortcomings on the efficiency of reauthentication in EAP-AKA protocol of 3GPP, such as, the Re-direction attack for personating WLAN AN and the transmission delay in roaming and refreshing session key processes, Localized Fast Signature Authentication Protocol (LFSA) is a more efficient protocol for security access in 3G-WLAN interworking network by adopting WLAN AN's ID verification, fast signature, off-line accounting and localized authentication mechanisms. LFSA improve the efficiency of reauthentication for 3G mobile users roaming and handover in WLAN networks and provides better services.