WiMAX與LTE間異質無線網路共構研究與效能提升

Abstract

本論文主要討論在LTE( Long Term Evolution)與WiMAX之間異質網路的共構問題，在未來4G系統營運的時候必然會遇到使用者同時擁有不同系統的帳戶，而異質網路系統間互相漫遊(Roaming)將可以解決使用者在使用上的不方便，最主要的目標就是能夠讓使用者察覺不到系統的切換。首先將會探討整個跨系統間換手(Inter-RAT handover)的流程，之中包含著實體層，MAC層以及IP層，並使用PMIPv6來整合兩異質系統間多重IP問題。探討整個流程之後，發現到之中存在著許多的效能瓶頸將會提升跨系統換手的延遲時間，所以我們提出了一個增進效能的網路架構，在兩系統的中間建立一台快取伺服器，此伺服器在我們假定的功能之下，希望可以達到預先連接並把所需要的對應參數存入快取伺服器，當執行跨系統換手時即可馬上讀取此參數節省延遲時間。 本論文之研究為： 一， 在不改動WiMAX標準規範的前提之下，建立LTE與WiMAX共構以及Inter-RAT handover 之機制。 二， 由於跨系統之換手牽涉到實體層往上到IP層，於是提出數學計算與Queueing Network結合之分析方法。 三， 加入快取伺服器以期縮短換手時間並提升成功率。

This thesis is about heterogeneous wireless network integration, we consider LTE(Long Term Evolution) with WiMAX ‘s case. When next generation technique is start to use, user may have different account in different wireless network system in the future. It’s convenient for user that each heterogeneous system can roaming to another. And the main objective is user will not notice that they are roaming to another system. First we will discuss the whole procedure about inter-RAT (Radio Access Technique) which across physical layer, MAC layer and IP layer. And we will use Proxy MIPv6 to solve multi-IP problem in heterogeneous network. After discuss the procedure, we will find that there exist some bottleneck which will cause unnecessary delay. Based on the analysis result, we bring out a new element to improve the performance about inter-RAT handover. We add a cache server between LTE and WiMAX. We expect to decrease inter-RAT handover delay by user “pre-connect”. Pre-connect will store the information we need into cache server.

Our main contributions are as follow: 1. We build up a Inter-RAT handover procedure in LTE integrate WiMAX scenario without changing WiMAX ’s standard. 2. Inter-RAT handover procedure across three different layer from physical to IP. So we analysis this procedure in meth way and queueing network model. 3. Decrease inter-RAT handover delay time by adding a cache server.