Reducing Handoff Delay in WLAN Using Selective Proactive Context Caching

Lee, Jen Funn (2008) Reducing Handoff Delay in WLAN Using Selective Proactive Context Caching. Masters thesis, University of Malaya.

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Continuous connectivity is one of the important requirements of Institute of Electrical and Electronics Engineers (IEEE) 802.11 Wireless Local Area Networks (WLAN) which allow user mobility while utilizing the network. However, handoff from the originally associated base station to another base station in the WLAN networks is an issue that affects the performance of delay sensitive multimedia applications such as voice and video. Handoffs can be divided into layer two and layer three handoffs. Layer two handoff is defined as a station movement from one base station to another base station within the same network whereas layer three handoff involves transition among different networks. Handoff at layer 2 consists of three phases including scanning, authentication and reassociation. In order to establish and keep service state information, a context transfer protocol is used to transfer service state associated with the station during handoff and this increases the overall handoff latency. As a security measurement during context transfer, base stations exchange messages to establish a secure channel between APs for transmitting associating STA context information. In order to reduce the overall handoff delay especially when context transfer protocol is applied, an approach called Selective Proactive Context Caching (SPCC) technique is proposed to proactively propagate the security context of the mobile client to a selected set of neighboring base stations before reassociation occurs. Selected neighboring base stations exchange link quality information of mobile clients through the Local Area Network (LAN) and this information is stored into cache memory. Based on the link quality information, the originally associated AP selects a set of neighbor APs and forwards the security context of the mobile station through the LAN. The SPCC technique was tested using the OMNeT++ network simulator. The simulation results show an improvement of 62.5% in reducing handoff delay due to reassociation. The reassociation delay was II reduced from 32ms for the conventional 802.11 handoff mechanism to 12ms when SPCC mechanism was applied. Finally, this approach required minor changes to the 802.11 standards.

Item Type: Thesis (Masters)
Subjects: Z Bibliography. Library Science. Information Resources > Z665 Library Science. Information Science
Date Deposited: 15 Jul 2013 07:17
Last Modified: 15 Jul 2013 07:17

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