應用於蜂巢系統整體服務之改良局部壓縮分散式動態頻道分配法則

Abstract

在這篇論文裡，我們所考慮無線通訊蜂巢系統下的一個重要問題是有哪些頻道分配法則(Channel Assignment Schemes)。且不同的頻道分配法則可以改善多少通話阻塞率(new call blocking rate)和交接強迫中斷率(handoff forced termination rate)是我們所要研究的。在未來將不只會有語音通話(voice calls)且數據通話(packet calls)的使用量將會日漸增加。所以需考慮的將會更複雜。我們專注在局部壓縮分散式動態頻道分配法則( Local Packing Distributed Dynamic Channel Assignment scheme )和防護頻道法則( Guard Channel scheme )。將這兩中法則結合，期望可以降低語音和數據交接強迫中斷率。從我們的模擬結果得知，數據通話雖然會重傳，但是其在交接時亦會產生阻塞，所以亦是可以提供對數據通話的交接保護，來降低數據交接強迫中斷率( packet handoff forced termination rate )，以達到可接受的阻塞率。

In this thesis, we consider a hierarchical cellular system (HCS) with two tiers where macrcells in the high tier provide broad radio coverage and microcells in the low tier support system capacity, and both jointly serve users of di?erent mobility. One important issue in the system is how best a channel assignment scheme can be designed to reduce the probability of new call blocking as well as hando? call forced termination. As expected, this issue becomes more complex when both voice calls and data-packet calls are considered. To stem on this issue, we focus on the Local Packing Distributed ynamic Channel Assignment (LP-DDCA) scheme and Guard Channel scheme, which are developed to smooth the hando calls. Speci?cally, we propose to combine the two schemes (with some modi?cations) to reduce the probability of hando? call forced termination for both voice and data-packet call services, subject to a tisfactory level of new call (including voice and packet-data calls) blocking rates. We conclude from our simulations that in order to have an acceptable hando? call forced termination rate, the packet-data calls, although they are often armed with re-transmission, also need to be protected for their hando?.