A Fast Handover Algorithm Of IEEE 802.11 Network Based On Pre-association On ESS

In recent years, large-scale WLANs based on IEEE 802.11 have been widely used. End-users may need to handover between different BSS frequently within large-scale, AC–thin–AP-combined networks. Services, such as Vo IP, video surveillance, remote cooperation, and remote control, have a relatively high requirement on the delay of network handover which can't be reached by current 802.11 standards. So decreasing the delay of handover is of great significance on the developing of various new services.To solve this problem, we propose a fast handover algorithm based on pre-association to the whole ESS(PAE). When an STA initially associates to a network, it is able to get the information of all APs in the ESS from its current associated AP for pre-association to all other APs in the network. Pre-association is achieved by current AP's collaboration relay, i.e., the current AP intercepts all management frames sent by the STA and sends these frames to the destination AP via a wired connection. A destination AP will insert these management frames to MAC layer on itself and send the response frame in the same way back to the STA with the help of the current AP. Thereby we achieve the communication between STAs and their destination APs without considering the real span distance limit. After pre-association, STA and destination APs cache their derived temporary key, and the destination APs will approve fast-handover according to the status of the cached temporary key when any handover happens. Through a re-association request, STAs can complete the handover process and encrypt the subsequent data transmission with the cached temporary key directly.We designed the above fast handover algorithm after the analysis of 802.11 network security protocols and standard handover processes. We proved the effectiveness of the algorithm by the achievement of implementation on Linux wireless routers. In the process of the implementation, we study the framework and workflow of Linux-based open source WLAN network card driver(ath9k) and the open source implementation of IEEE 802.11i(hostapd/wpa_supplicant). We designed all the models of the PAE algorithm in the router with some Linux programming techniques and open source network utilities.The results show that PAE algorithm reduces the delay of authentication and key derivation to practically 0, which effectively reducing the currently existing handover delay, and meanwhile it maintains the security provided by 802.11 i standard. This algorithm is significantly helpful to high delay sensitive WLAN applications such as rail train/traffic control.