ZigBee網路之主幹感知的網路形成機制

Abstract

本論文針對無線感測網路（Wireless Sensor Network）提出一套可以舒緩熱點問題（Hot-spot Problem）以至於延長網路生命週期的繞送機制。 無線感測網路常用於偵測周圍環境，將相關資訊傳回給基地台（Base Station），方便管理者根據資料進行判斷與反應；無線感測網路由許多具有電量限制的感測節點所組成。感測節點會消耗許多的電力在傳送資料上。然而無線感測網路會有熱點問題存在，亦即距離基地台較近的節點會有較重的資料轉送負載，所以這些節點會先耗盡電能而損耗。然而在感測網路的實際部署環境中，某些感測節點可持續接電或較容易更換電池，我們將這些感測節點統稱為具電節點（Power-node）。本論文即是以具電節點為主幹，提出一套的主幹感知的網路形成機制（Backbone-Aware Network Formation; BANF）來舒緩熱點問題造成的影響。 我們透過具電節點建立起主幹網路（Backbone Networks），透過主幹網路將資料負載分散至多個具電節點。BANF具有兩個特色：ぇ 建立以具電節點為樹根（Root）的子樹；え 提出了當具電節點突然損壞的主幹網路臨時修復機制。經由在NS2網路模擬平台的實驗，本研究所提出的主幹感知網路形成機制相對於ZigBee無線感測網路，依據不同的網路拓樸可以延長193%至310%的節點平均運作時間。

In this thesis, we propose a routing mechanism that can mitigate the hot-spot problem of wireless sensor networks (WSNs) so as to extend the network lifetime. A WSN consists of a coordinator and many sensor nodes that periodically collect and report to the coordinator the sensed information. With such periodical transmission, a sensor node may exhaust its energy sometime if it has limited energy resources. Moreover, the energy consumption may further be aggravated by the hot-spot problem that commonly exists in most WSNs; that is, sensor nodes closer to the coordinator tend to relay more traffic, and will exhaust their power sooner than others. However, in most deployments of sensor networks, there exist some nodes, henceforth referred to as power-nodes, with fixed power supplies or easy to replace if malfunction. In this thesis, we propose a Backbone-Aware Network Formation (BANF) scheme to mitigate the influence of hot-spot problem. We use power-nodes to construct the backbone of a network and route information toward a backbone power-node first, or the coordinator if it is closer than other power-nodes. The power-nodes then route the traffic toward the coordinator through other power-nodes in the backbone. Therefore, BANF can distribute traffic loads to more spots (nodes near backbone power-nodes) and alleviate the hot-spot problem of WSNs. BANF has two features: (1) power-node based subtrees and routing, and (2) fault tolerance mechanism for power-node failures. Results from NS2 simulations show that BANF can prolong network lifetime about 193~310%, compared with ZigBee under various network topologies.