以額度為基礎之動態選網系統資源配置

Abstract

在人口密度高且基地台站址不易尋找情形，同一電信業者通常會將不同技術所屬網路之基地台共站方式建構，而且以各種技術同時提供服務。針對同一家電信業者之多個無線技術，在多網共構基地台之涵蓋範圍內的用戶有多種網路可供選擇。目前商業化之多模網卡，往往是由網卡連線程式來決定要使用哪個網路，通常網卡連線程式會優先選擇實體層速率最快的網路，然而這種方式並沒有考慮到整體網路的真實使用情況以及使用效率，會使服務品質降低，且無法讓資源獲得有效的分配。 因此我們提出一種選網演算法，額度控管兼平衡網路使用率演算法(Quota-based utilization balance algorithm，QUBA)，採取HSPA+、HSDPA、UMTS三網共構的網路。其設計的精神如下，用戶端一開始的選網動作，全部統一交由網路管理系統端來處理，並搭配經由設計之演算法做為分配網路的決策，系統端可以根據目前系統的狀況計算出實際每人可分配到的頻寬。對於用戶來說，能選擇到當時實際可分得頻寬最高的網路；對於業者來說，也能有效管理網路以及掌握各個網路利用率之動向，避免發生HSPA+網路滿載，而HSDPA網路卻閒置的情形發生，並使兩個系統的頻譜利用率達到一定的平衡效果。模擬結果顯示能達到三大目標並優於其它現存演算法。(一)提升整體用戶之滿意度(Total Utility)，站在業者的立場，照顧到了整體的用戶對於網路連線品質及速率的需求，站在使用者的立場，使用者能被系統安排進入當時實際可分得最大頻寬的網路，而非只看實體層傳輸速率。(二)減少新進使用者被系統拒絕連網的機率(Blocking Probability)。(三)讓前兩個網路的利用率(Utilization)達到一定效果的平衡，避免最高速網路壅塞，而次高速網路卻閒置的情形發生，提升利用率。

Due to the fact that it is difficult to deploy base stations (BSs) in a region with high population density, an operator usually co-locates various networks in a BS and serves users’ demands simultaneously with those networks. Existing 3.5G data cards usually select networks with the highest physical data rate as their priority choices such that the radio resources may not be efficiently and equally utilized in a multiple network environment, even when the network with the highest rate is already congested. In this thesis, we therefore propose a dynamic network selection algorithm via a quota-based admission control design for accommodating access requests in a multi-network (HSPA+, HSDPA and UMTS) co-location environment, which is common for today’s 3G operators. In most commercial networks, the accesses of individual users are often charged at a flat rate. In such a charging scheme, a few extremely heavy users may degrade the performance and the fairness of the whole network. As a result, we propose an algorithm called Quota-based Utilization Balance Algorithm (QUBA), designed to settle such a problem and also maximize the overall utility of all users. The design philosophy of QUBA is to let the system utilization in the 2 fastest networks, HSPA+ and HSDPA, be statistically balanced and sufficiently utilized. Performance metrics in terms of the overall system utility (i.e., the satisfaction index), the blocking probability, and the system utilization are investigated. From simulation results, it is shown that the QUBA algorithm has significant