行動通訊系統之適應型通道配置技術設計與效能分析

Design and Performance Analysis of The Adaptive Channel Assignment Algorithm in Mobile Cellular Systems

劉獻文(Hsien-Wen Liu)

指導教授 ： 涂世雄

中原大學/工學院/電機工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200061

摘要

論文摘要
在行動通訊中，由於每個細胞基地台所配置的通道數目有限，導致當基地台的所有通道數同一時間都被使用，如果有新的使用者要加入，則需要向鄰近的基地台借通道。在借通道的同時，行動交換中心（MSC）需要將與此通道相同頻率的通道鎖住，以避免共通道之間的干擾。因此如何減少共通道被鎖住的數目，並且對於基地台負載不平衡及ping-pong現象，都是通道演算法的重要課題。本論文將針對這些問題提出解決方法。

改良型通道配置演算法
在本論文中，我們將介紹基本的通道配置策略相關的觀念，同時簡述一些已經被提出借通道策略的優缺點。我們基於借通道的觀念提出了適應型通道配置演算法，來解決借通道所產生的問題。
在我們提出的通道配置技術包括以雙臨界值定義出基地台輕負載、重負載兩個臨界點，新的共通道閉鎖的演算法以及借通道判斷法則。第一項，可以使基地台彼此間的負載加速趨於平衡，又可以避免只定義一個臨界點所衍生的ping-pong現象，藉以減少MSC的資源浪費。第二項，由於鎖住共通道的數目可以被減少，因此可以提高整個系統的效能。第三項，藉由借通道判斷法則可以選擇與本身基地台最為合適之通道，再向此目標基地台借通道以提高通道使用效率。這個新的演算法具有的優點如下：
(1) 此新的技術在借通道時具有及時性。
(2) 因為借通道時，被借的基地台具有優先順序，從鎖住同通道數目少的基地台
開始借，因此提高系統效能。
(3) 可使基地台彼此間負載加速趨於平衡。
(4) 使用新的細胞輕、重負載定義可以避免ping-pong現象。
(5) 減少共通道的鎖住數目，可以提高通道使用率。

關鍵字

共通道閉鎖 ； 適應型通道配置 ； 通道配置 ； 基地台負載 ； 借通道

並列摘要

Abstract

In this thesis, we propose the adaptive channel assignment algorithm with a co-channel locking scheme, a channel borrowing selection criteria and use two thresholds to definition of availability of cells in the cellular mobile systems. The co-channel locking scheme and the channel borrowing selection criteria can improve the capacity of the cellular systems. On the other hand, the definition of availability of cells can avoid the ping-pong phenomenon and accelerate the balance of loads.
In a previous proposal approach, the number of co-channels of a lent cell to be locked is fix to three. However, by analyzing some kinds of compact patterns of cellular systems, it can be found that the number of co-channels of the lent cells to be locked can be reduced. Hence, by our research, we propose a co-channel locking scheme and a channel borrowing selection criteria in channel assignment to improve the capacity of the cellular systems.
Traditionally, several schemes use single threshold to define the availability of cells. In this case, if the call arrival rate is high, a cell with a coldness degree near to the value of the threshold may lapse into a ping-pong state being switched back and forth between cold and hot states, resulting in useless channel borrowing and lending. To overcome this problem, two thresholds for defining the availability of cells have been proposed. In this thesis, a new definition of availability of cells with two thresholds is presented not only absolutely to avoid the ping-pong phenomenon but also to accelerate the load balance. In our study, the single threshold scheme is suitable under low traffic load condition. However, the single threshold schemes perform less than our two thresholds scheme under moderated or heavy traffic load conditions. Finally, we believe the adaptive scheme can be increase mobile cellular system performance.

並列關鍵字

channel borrowing ； channel assignment ； co-channel locking ； adaptive channel assignment algorithm ； base station load

參考文獻

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