數位歐式無線電話頻道分配方法與通話交遞準據之研究

Abstract

在第二代的行動通訊系統中,數位歐式無線電話系統已廣泛的被歐洲所接受。 此系統使用動態頻道分配及手機控制的交遞技術。在歐洲通訊標準組織所規範的歐式數位無線電話系統中, 並未明確的將頻道分配及交遞的功能加以標準化。系統製造商及作業 者可以自行訂定這些功能的運作細目。 在這篇論文中,我們探討在歐式無線電話標準中有關頻道分配及交遞之參數, 並研究一些頻道分配方法及交遞準據的性能。 在頻道分配技術的研究方面,我們尋求能獲得高的訊擾比及低的服務品級的方法, 其中服務品級是以電話阻絕機率及通話中斷機率來量度。我們所考慮的頻道分配 和交遞技術演算法基本上是依藉著訊擾比, 在交遞方面亦考慮對於其他基 地台的訊號強度是否大於目前基地台訊號強度一個預定的標準值以上,以作交遞與否 的決定。不同的演 算法中存在若干相異之處,例如不同的頻道順序排列和交遞延遲時間長度等等。 在整個的研究方面,我們以服務品級和交遞數目來作為其 性能的量度,也就是當手機執行一個初始或是交遞電話時。 服務品級數目越大,系統的效果就越差。 交遞數目越大,則系統的負載就更重。模擬結果顯示:我們在這篇論文所提出的方法比 根據數位歐式電話規格訂出的參考方法效果好一點。

Among the second-generation indoor wireless communication systems, the DECT has received wide acceptance in Europe. DECT employs dynamic channel allocation and mobile-controlled handover. In the ETSI DECT Recommendations, the channel allocation and handover procedures are not standardized, thus the system manufactures and operators have considerable freedom in specifying the details of these functions. In this thesis, we examine the parameters defined in the DECT documents that are related to channel allocation and handover, and we study the performance of some channel allocation method and handover criteria in the DECT framework. In our study of the channel allocation algorithms, we gear at finding techniques that yield high CIR and low GOS measured in terms of call blocking and call dropping probabilities. The considered channel allocation and handover algorithms are all based on measurement of the CIR if the signal strengths to different base statios, deciding on handover if the CIR is lower than a predefined threshold or the signal strength to another base station is stronger than a predefined threshold than current base station. The details differ for different algorithms, for example, the difference of channel order and the length of the handover delay time. The performance measure in our study is the GOS values and the handover numbers when a portable initiates an initial or a handover call. The larger the GOS value, the poor the system performance. And the larger the handovr numbers, the heavier the system loading. Simulations results show that the methods in this thesis perform a litte better than the method according to DECT specification.