B4G行動通訊系統中的自組織網路演算法

Abstract

隨著4G行動寬頻技術推波助瀾，電信營運商面對行動數據量爆發性成長，莫不設法增建基地台並透過競標取得更多無線頻譜資源，以綿密的無線訊號涵蓋範圍與數據承載量來滿足消費者殷切的需求。3GPP組織為了提昇消費者的體驗滿意度並協助電信營運商降低整體網路的營運成本、提昇其競爭力，提出了自組織網路(Self-Organizing Networks, SON)技術架構，擬針對自動化進行網路參數調控、網路維運最佳化、基地台中斷服務即時偵測與補償等應用情境，希望建立一套能快速回應、有效管理4G行動網路的管理技術。SON網管技術進一步可分為自我組態(Self-Configuration)、自我優化(Self-Optimization)與自我修復(Self-Healing)等三個範疇，其核心精神是應用4G行動網路自動化配置與調控之技術，來取代原本仰賴大量人工所需之網路佈建與維運成本，使電信營運商在有限的頻譜資源下優化網路傳輸效能，當行動網路發生服務中斷時也可立即偵測，快速啟動自動修復之機制，以提昇其營運之競爭力。然而，3GPP雖規範了SON之技術架構與主要功能，但針對達成各個SON功能之演算法設計與實作卻缺乏論述，故本篇論文聚焦提出自我優化與自我修復SON演算法之設計，並藉由系統化分析與模擬驗證，來與先前技術作客觀之評比。 我們使用不同參數進行實驗模擬，在不同的模擬環境中，相較於比較對象，所提出的蜂巢中斷補償(Cell Outage Compensation, COC) 與動態資源分配 (Dynamic Resource Allocation, DRA) 方法，可有效的提昇蜂巢中斷使用者(Cell Outage User )與一般使用者(Regular User)的平均訊號與干擾雜訊比(Signal to Interference and Noise Ratio, SINR)。另外，我們將可以成功與基站進行連線的SINR門檻值設為SINR ≥ -3 dB。從模擬結果中可看出所提COC+DRA方法，挽救回的Compensated User (SINR ≥ -3 dB )約為91%，功率調控蜂巢中斷補償( power-base cell outage compensation, P-Base COC) 方法約為81%，調校引導功率蜂巢中斷補償機制(adjusting pilot power based mechanism, APPBM)約為79%。COC+DRA方法能挽救的 Outage User的比例是三者中最高，且SINR是三者中表現最好的。而在Regular User 方面，SINR ≥ 5 dB的使用者，COC+DRA約為81%， P-Base COC約為77%，APPBM約為71%，由此可知COC+DRA除了能提高Compensation User的SINR，維持Compensation User SINR的同時，並無犧牲其他Regular User的傳輸品質，能有效提昇整體系統與使用者的傳輸容量與效能。

Responding to the trend of 4G mobile broadband technologies and the corresponding explosive growth of mobile data traffic, telecom operators have increased the number of base stations and obtained more radio spectra to meet consumer demands for wireless signal coverage and vast data carrying capacity. To assist telecom companies, the 3rd Generation Partnership Project (3GPP) has proposed self-organizing network (SON) architecture, which is aimed at effectively managing 4G services in real-world scenarios. The core of SON technology is to auto configure and regulate 4G services to avoid the considerable workforce and costs required for conventional network deployment and maintenance. Moreover, it enables telecom companies to optimize network transmission efficiency under limited spectra and immediately detects service interruptions and triggers recovery mechanisms. However, although the 3GPP defined the SON architecture and its main features, the design and implementation of the algorithm is lacking, and each SON feature is achieved separately. Consequently, this thesis is focused on the design of SON algorithms for self-optimization and self-healing. After objectively comparing present work and previous studies by systematic analysis, this study verifies its findings with simulations. The simulations shows the average SINR of compensated users and regular users using the proposed cell outage compensation (COC) and dynamic resource allocation (DRA) algorithm with various parameters and the reference algorithms. The proposed COC + DRA was used for cell outage compensation, the average SINR is obviously higher than P-Base COC and adjusting pilot power based mechanism (APPBM). In the simulation, the probability of restored connections (i.e., SINR ≥ -3 dB) for compensated users using COC+DRA (weight of regular user =1; weight of outage user = 2) was approximately 91%; the probability using P-base COC was approximately 81%; and the probability using APPBM was approximately 79%. Thus, COC+DRA had the highest probability among the three algorithms of restoring connections for outage users and the highest SINR. As shown in simulations, approximately 81% of regular users experienced SINR of above 5 dB using COC+DRA, whereas approximately 77% and 71 % of regular users experienced this SINR using the other two algorithms. The COC+DRA algorithm effectively improved the signal quality of compensated users to facilitate stable transmission and simultaneously maintained the fairness and transmission efficiency of other regular users.