應急蜂巢式行動通訊網路的頻寬分配


Bandwidth Allocation For Contingency Cellular Network


吳雲鼎

大型天然災害會癱瘓通訊系統,嚴重影響到救災效率,本論文旨在快速進行可用連外頻寬分配,供應急通訊系統使用。無線通訊技術的成熟,為使用者帶來極大的便利性,但當發生大規模的地震或強烈颱風等重大天然災害時,通訊系統卻常常因架構等因素,隨著電力與交通系統的損毀而癱瘓。由歷年大型災變中多數災區內之行動通訊系統全面中斷即可印證行動通訊系統其實是極為脆弱,而有效運作的通訊系統卻是災情傳遞、資源調度以及互助協調是否順利的關鍵因素。

本篇論文所探討的應急通訊系統是利用倖存的連通基地台和斷訊卻沒有損毀的基地台,以無線電連接起來建構一個臨時性的通訊系統,稱為應急蜂巢式行動通訊網路(Contingency Cellular Network,CCN)。由於CCN的連外頻寬有限,大量話務將造成通訊系統壅塞,影響重要訊息傳遞,且災區各個地方受災情況不盡相同,使得 CCN 的頻寬資源需視各地災情緊急程度與需求進行規劃配置,以充分發揮頻寬效益傳遞重要資訊。本論文主要在探討如何在CCN網路拓樸已決定的情況下進行頻寬分配,以達到最大的救災效益。因此我們提出一適合 CCN 樹狀結構的頻寬分配優化模型,以追求救災效益的最大化,這個模型可供使用者(救災指揮單位)系統化的解決 CCN 頻寬分配問題。

本論文所提出的頻寬分配模型包含 CCN 樹狀拓樸、基地台數目、可用之連外頻寬資源限制、各基地台Backhaul頻寬限制、基本頻寬需求限制、差異化之通訊品質通道和效益遞減函數。我們證明此模型是NP-Hard問題,並提出一個考慮各基地台的災情緊急程度以及通訊品質需求差異而進行快速頻寬分配的演算法,此演算法透過計算頻寬分配總救災效益決定優劣。經實驗,可快速得出接近最佳解的頻寬分配結果。?

When stricken by a large-scale disaster, the efficiency of disaster response operation is very critical to life saving. We propose to build a contingency cellular network to support emergency communication in large scale natural disasters by connecting disconnected base stations. This thesis addresses the bandwidth allocation problem. The advance of mobile communication technologies has brought great convenience to users. Cellular phone becomes the first communication tool most people would use in emergency. However, cellular networks were usually crashed in earthquake, typhoons or other natural disasters due to power outage or backhaul breakage. Unfortunately, the efficiency of communication system is a critical factor to the success of disaster response operation such as resource allocation as well as coordination of rescue and relief operations. We designed a contingency cellular network (CCN) by connecting physically intact but service-disrupted base stations together with wireless links. As the bandwidth resource in CCN is limited, a smart bandwidth allocation to facilitate prioritized bandwidth sharing will maximize the contribution of CCN to the disaster response operation. We model the CCN Bandwidth Allocation Problem into a Nested 0-1 Knapsack Problem aiming to maximize disaster operation efficiency. The problem is proven to be NP Hard. We also design an efficient heuristic algorithm to solve the problem when it is needed in urgent.