應急行動通訊系統設計


Design of Contingency Cellular Network


黃智賢

當大型災害來臨,通訊系統對救災效益具有不可或缺的重要性。然而, 一般公眾通訊系統,如行動通訊網路等,常因各種不同因素導致系統癱瘓。 在災變初期,外援常因交通運輸問題無法即時進駐災區,而需仰賴數以萬計甚至 數十萬的災區在地志工投入救災工作。而現存多個緊急通訊系統的佈建, 需仰賴良好的交通運輸,不幸的是,部分道路和橋樑常因大型災害而斷裂或變型, 導致災區對外交通運輸中斷,無法快速的將緊急通訊系統的網路元件, 運送至災區佈建。再者,因造價之故,系統容量僅能提供小部分專業救災團隊使用, 而無法提供給數量龐大的救災志工使用。

我們提出應急行動通訊系統 (Contingency Cellular Network, CCN) 以提供災區救災工作的緊急通訊。 我們在歷年的災害中發現行動通信系統斷訊時大部分基地台的結構是完整的, 但因失去與核心網路連線能力或電力供應,而無法提供服務,成為孤立基地台。 應急行動通訊網路(CCN)利用這些孤立基地台搭配無線通訊與衛星通訊技術 建置一多重跳接無線網路,以恢復孤立基地台與核心網路連線能力; 並配備發電機,提供電力,使孤立基地台可提供有限的服務。 救災志工和災民無需使用特殊手持設備或額外的訓練,只需使用原有的手機, 即可使用CCN的應急通訊服務。CCN可於第一時間, 提供大批救災志工和災民通訊服務,以提高救災效益,因而拯救更多寶貴的生命。

本論文主要聚焦在應急行動通訊系統設計所衍生出的相關議題,如 應急網路需求分析、 系統架構設計、網路拓樸規劃、網路頻寬規劃、佈署行程規劃等議題。 本論文針對網路拓樸規劃、網路頻寬規劃、佈署行程規劃問題以數學模式進行塑模, 並證明這些問題為NP-Hard問題。因網路拓樸規劃、網路頻寬規劃、佈署行程規劃需緊急完成, 我們也提出啟發式演算法快速解決這些規劃問題。實驗結果顯示, 這些啟發式演算法均具良好的效能。

關鍵字 — 災難管理、緊急通訊、行動通訊、 Ad Hoc網路、網路拓樸、佈署行程、頻寬管理

Communication system is crucial to the efficiency of disaster response operation in the large-scale disaster. However, communication systems, such as cellular networks, usually crashed due to various causes making coordination among disorganized disaster responders extremely difficult. Unfortunately, rapid deployment of many existing emergency communication systems relies on a good transportation system, which is usually not available in a catastrophic natural disaster. We proposed a Contingency Cellular Network (CCN) for emergency communication by connecting disconnected base stations together with wireless links to construct a wireless multi-hop cellular network. CCN can support existing mobile phone users with reduced capability. Such a system can support a large number of disaster responders in the early hours of a catastrophic natural disaster, thus save many lives. Our research addresses the design issues of the network topology of CCN, such as network topology planning, bandwidth management, deployment scheduling and etc., and we take the degree of emergency and population of each stricken area as the priority measure as well as the available resources as the constraint to determine the network topology. Mathematical models of these design issues are proposed and proved as NP-Hard problems. Since the network topology, bandwidth management, deployment scheduling are needed in urgent, we propose heuristic algorithms to solve these problems quickly. Finally, we evaluated the proposed algorithms by simulation. A significant improvement in resiliency is reached. Keywords — Disaster Management, Emergency Communication, Mobile Communication, Ad Hoc Network, Deployment Scheduling