Implementation Schemes And Performance Optimization Of Mobile IPv6 Techniques Applied In Wireless Local Area Networks

With the wide application of IEEE 802.11 based Wireless Local Area Network(WLAN),mobile devices equipped with Wi-Fi interface have become increasingly popular.Wi-Fi interface is used in mobile phones,laptops and other daily devices.Moreover,some kinds of sensor nodes in the Internet of Things(Io T)take advantage of Wi-Fi as well.Therefore,an important research topic in mobility management is how to maintain the network connection for the Wi-Fi interface enabled mobile devices in movement.The IEEE 802.11 based WLAN only supports link-layer but not network-layer mobility management.As a result,the network connection may be interrupted when a mobile node(MN)moves into a new subnet.This shortcoming of the IEEE 802.11 standard can be remedied by the Proxy Mobile IPv6(PMIPv6)protocol,a widely-used network based mobility protocol,which has many advantages including the MN being not involved in exchanging mobility related signaling.In this dissertation,we study the mobility management issues in different scenarios of WLAN and the implementation of PMIPv6 protocol in infrastructure WLAN,aiming at reducing handoff delay and packet loss ratio and optimizing routing.The main work and innovation are as follows:Firstly,the scheme to implement PMIPv6 in IEEE 802.11 infrastructure WLAN is proposed.The existing work,which implements PMIPv6 in WLAN,only focus on the structure in which a MAG manages only one AP.Therefore,the scheme that uses Extended Service Set(ESS)–based architecture is proposed to implement the PMIPv6 protocol for IEEE 802.11 infrastructure WLANs.The key signaling messages,together with their time sequences for the mobility management,are designed.To analyse the performance of the proposed ESS-based scheme,we use a square and a regular hexagon to stand for a basic service set(BSS)separately,based on which the probability of the MN crossing an ESS boundary is derived.Furthermore,the handoff delay in the proposed scheme is derived so that the performance of the proposed scheme is analyzed.Numerical analysis indicates that the proposed scheme considerably outperforms the existing one in terms of handoff delay when the delay between Mobile Access Gateway(MAG)and Local Mobility Anchor(LMA)is relatively large.Secondly,the scheme to reduce handoff delay and packet loss ratio in the Wireless LAN Controller(WLC)based WLAN is proposed.With the increase of the scale of WLAN,WLC is recommended to manage the APs in large scale WLAN.In the WLC based WLAN,the mobility signaling will be transferred from AP to WLC,and only when the WLC finishes processing the message can the signalling take effect,which increases the handoff delay greatly.To resolve this issue,the MAG chain is used in this dissertation to reduce packet delay in the WLC based WLAN.A general expression of the probability of MN's crossing the coverage of a MAG is derived,which is used to analyze both the MN's dwell time in a MAG and the duration of a session.Additionally,both handoff delay and packet delivery delay in the proposed scheme are derived,based on which the Optimization Problem is formulated to minimize delay.By solving the OP,the optimal MAG chain length is found.Numerical analysis indicates the proposed scheme outperforms the existing one in terms of delay when the delay between LMA and WLC is relatively large.In addition,the proposed scheme can reduce packet loss due to delay limitation.Lastly,we study the scheme to apply distributed mobility anchoring to the WLC based WLAN and use two-level pointers to further reduce handoff delay and optimize routing.The distributed mobility management(DMM)allows an MN to choose the nearest access router as its anchor when a new session arrives.Therefore,DMM can acquire lower handoff delay and near-optimal routing so that it can be applied in the WLC based WLAN.However,the anchor is chosen at the beginning of a session and keeps unchanged during the MN's movement,which may bring in the problem of large handoff delay and sub-optimal routing problem in the case when the MN triggers many handoffs in a given session.To resolve this problem,the scheme that applies two-level pointers,called the low-level pointer and the high-level pointer,is proposed.The low-level pointer is similar to the MAG chain and used to reduce handoff delay,and the high-level pointer optimizes routing path by updating the MN's location to the LMA or correspondent node(CN).Therefore,the anchor in a session can be dynamically changed.Furthermore,the handoff delay in the proposed scheme and the existing schemes are derived.Numerical analysis and simulation results show that the propose scheme can reduce handoff delay of DMM.The schemes introduced in this dissertation are applicable to various WLAN scenarios and help in developping the mobility management protocols for other wireless networks.