| Summary: | 博士 === 國立中央大學 === 電機工程研究所 === 96 === The next generation of mobile communication will contain multiple wireless access technologies such as IEEE 802.11, IEEE 802.16 and WCDMA which form a heterogeneous access network seamlessly. How to integrate those different technologies is a great challenge. Because of each network access technology provides different levels of coverage and quality of service (QoS) as well as cost to end user, thus resource allocation, mobility management and QoS requirement are important issues in each system. As a result, every access technology provides some mechanisms and protocols to deal with those issues. However, these mechanisms and protocol used in different access system are different, so it is hard to provide seamlessly handover in inter connected system.
Although there are many different issues in Beyond Third Generation (B3G) network, thanks to the All-IP network architecture proposed to implement B3G network and which can help us to integrate these heterogeneous wireless network using the same language, therefore, we propose several schemes to improve the network performance and ability of mobility management within heterogeneous network.
This thesis presents four major contributions. First, we propose two mobility management schemes in two-tier cellular networks and compare the system performance. In addition, an overflow threshold is assumed in the mobility management scheme to avoid too many overflows occurred to reduce the blocking and dropping probabilities. Then, we propose a modified EDCF scheme, M-EDCF, to improve the Quality of Service (QoS) in the IEEE 802.11e wireless network which provides relative priorities by adjusting the size of the Contention Window (CW) of each traffic class. We also propose several schemes that regulate backoff contention window adaptively to achieve more fairness between ACs. Finally, we extend HMIPv6 Binding Update message to support Call Admission Control (CAC) schemes. These CAC schemes can reduce the probability of the handoff dropping and cell overload, and limit the new call blocking probability.
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