無線網路中的行動管理與服務品質改進

QoS Improvement and Mobility Management in Wireless Networks

林文彥(Wen-Yen Lin)

指導教授 ： 吳中實

國立中央大學/資訊電機學院/電機工程學系/博士(2007年)

摘要

隨著無線通信的進步和網路多媒體服務的廣大需求，行動通信的發展，可說是日新月異，而下一世代的無線通訊更是百家爭鳴。就目前的發展，並沒有任何單一存取技術，能夠贏得壓倒性的勝利。是以，混合型態的異質網路，採用共存方式呈現的局面將無法避免。現今的接取技術,如IEEE 802.11，GSM，GPRS，WCDMA/UMTS，IEEE802.16等規格各有所長，應用範圍與傳輸速度也有所不同。在資源分配、行動管理、服務品質需求上更是大相逕庭，如何整合眾多技術規格，便是未來最重要的課題，其中ALL-IP的網路架構，更是未來發展的重點與整合成功與否的關鍵 ，因此如何整合這些異質網路的資源，跨越行動服務藩籬即是本論文主要的研究目標。
本文分四大部份來探討異質無線網路中的行動管理與效能改進。首先討論All-IP環境下異質網路行動管理的效能改善，尤其針對蜂巢式行動網路中，藉由交換訊息的抑制，來降低封包阻隔率與遺失率。接著，我們把重點擺在802.11e無線網路的服務品質改進，雖然IEEE 802.11已是目前最廣泛的無線區域網路的標準，然而對於服務品質的控管卻是近幾年才被提出來討論。所以我們特別調整IEEE 802.11e EDCF的規格，滿足不同使用者對QoS的要求。再者，我們提出動態允入控制調整方法，來確保無線網路的公平原則。模擬結果顯示，我們的方法，不會因為只強調即時訊務的重要性，而完全犧牲了低優先權的資料。最後，我們將採用Mobile IPv6的移動管理技術及階層式架構，運用行動偵測允入控制的方法，降低系統換手的失敗率。

關鍵字

允入控制 ； Mobile IPv6 ； 無線網路 ； 服務品質保證 ； 行動管理

並列摘要

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.

並列關鍵字

Mobility Management ； QoS ； CAC ； Mobile IPv6 ； Wireless Network

參考文獻

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