Design and Performance of Wireless Local Loop
|關鍵字:||阻塞率;通話遺失率;交遞;無線區域迴路;Blocking Probability;Call Loss Probability;Handoff;Wireless Local Loop|
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.