無線區域迴路之設計與效能

Abstract

無線區域迴路經由無線界面提供雙向通訊服務給靜止或接近靜止的用戶。與有線區域迴路相比較，無線區域迴路具有容易安裝鋪設與資源集結等優點。資源分配是無線區域迴路設計與效能的重要課題。根據各基地台的無線電訊號涵蓋(也就是細胞)，本論文研究三大類無線區域迴路的細胞架構：1.基本型、2.覆蓋型、3.重疊型。在基本型無線區域迴路，細胞彼此不相互覆蓋或重疊。在覆蓋型無線區域迴路，巨細胞可以完全覆蓋多個微細胞。在重疊型無線區域迴路，細胞與其他細胞可以部份重疊。我們提出數學分析模型來探討這些架構的系統效能。所有的數學分析模型皆經由電腦模擬實驗來驗證。基於這些數學分析，我們證明得到重要結果：無線區域迴路之通話阻塞或通話遺失，和通話時間長度的分布無關，只和通話時間長度的平均有關。此外，我們針對覆蓋型與重疊型無線區域迴路，個別提出新的通道分配法則來降低通話阻塞與交遞次數。並且，我們也列舉一些無線區域迴路通道分配的設計準則來避免資源瓶頸。

Wireless local loop (WLL) provides two-way communication services to stationary or near-stationary subscribers via air interface. Compared with the wireline local loop, WLL offers advantages such as ease of installation and deployment, and concentration of resources. Resource allocation is an important issue for WLL design and performance. According to radio coverage of base stations (i.e.,cell), this dissertation studies three types of WLL cell structures: a basic WLL, the WLL with cell overlay, and the WLL with cell overlap. In the basic WLL, there are non-overlay and non-overlap cells. In the WLL with cell overlay, a macrocell overlays with several microcells. In the WLL with cell overlap, cells are partially overlapping with each other. Analytic models are proposed to investigate their system performance. All of these models are validated against simulation experiments. Based on these models, we prove that call blocking/loss of these WLL networks is not affected by the call holding time distributions, but is only dependent on the mean call holding times. Furthermore, new channel allocation schemes are proposed to reduce call loss and handoff for the WLL with cell overlay and the WLL with cell overlap, respectively. Moreover, we illustrate some design guidelines for WLL resource allocation to avoid bottleneck resource.