GPRS/UMTS 行動通訊系統之不等機率隨機移動模型之研究

A Non-uniform Distribution Random Walk Model for GPRS/UMTS Mobile Communication System

施正遠(Cheng-Yuan Shih)

指導教授 ： 李建誠

元智大學/工程學院/通訊工程學系/碩士(2005年)

摘要

GPRS/UMTS網路是目前行動通訊系統中，發展最完整的其中一種，它利用資料庫記錄來追蹤使用者的位置，以隨時傳遞必要的資訊到正確的位置；因此，行動裝置 (Mobile Station, MS)必須在經過一段移動後，向系統執行位置更新程序，並更新系統資料庫內MS的紀錄。不斷地更新資料庫系統是非常耗費成本的，在通訊網路的行動管理中，通常會將數個細胞集合成一個叢集，透過減少位置更新的次數來降低網路運作成本。但當MS被以細胞叢集為單位追蹤時，由於系統不知道MS位在叢集內的哪一個Cell；因此，在有資料必須傳遞給MS時，系統必須針對所叢集內的所有細胞發出呼叫，這樣卻又造成呼叫成本的提高。

在近期一些減少GPRS/UMTS網路成本的研究中，採用了等機率隨機移動模型作為移動機率估算，但實際上，MS移動應該具有方向性；因此，我們設計一個能夠找出馬可夫程序內狀態改變路徑的方法，我們稱作馬可夫查表式路徑搜尋法 (Markov Look up Table for Path Searching, MLTPS)。我們可以透過MCTSP的結果，計算精確機率，以及進行MS可能路徑的猜測，達到減少呼叫成本的浪費。

關鍵字

馬可夫查表式路徑搜尋法

並列摘要

GPRS/UMTS is one of the well-developed mobile communication networks. It delivers information to the correct location by using the record in database used for location tracking. Therefore, mobile station (MS) must perform a location update procedure after moving across a threshold. The location update procedure is used to update the MS location record in system database. However, the cost of location update is expensive. In cellular network mobility management, cell cluster is used to reduce the operation cost by lowering the times of location update. However, in the cell cluster mechanism, because the system does not know which cell the MS is located on, it has to broadcast the paging signal to all cells which located on the cell cluster when a paging signal is sent to MS. As a result of broadcast, the paging cost is increased.

In the past researches about reduction of the operation cost in GPRS/UMTS networks, they almost based on uniform distribution random walk model. Actually, the MS movement should have direction. For this reason, we propose a method for Markov process path searching, called Markov Look up Table for Path Searching (MLTPS). MLTPS can be used to compute accurate probability by non-uniform distribution for random walk model, and to predict the probable path for MS to reduce the paging cost.

並列關鍵字

MLTPS

參考文獻

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