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| Title: | A study of high performance medium access control protocols for IEEE 802.15.4 Zigbee wireless personal area networks |
| Other Titles: | IEEE 802.15.4 Zigbee個人無線網路上高效能媒介存取控制層之研究 |
| Authors: | 施雲嚴;Shih, Yun-yen |
| Contributors: | 淡江大學電機工程學系博士班
許獻聰;Sheu, Shiann-tsong |
| Keywords: | 連鎖碰撞;隱藏節點;感測網路;無線個人區域網路;collision chain;hidden node;Sensor Network;wireless personal area network (WPAN) |
| Date: | 2009 |
| Issue Date: | 2010-01-11 07:11:52 (UTC+8) |
| Abstract: | 新興的無線個人網路 (wireless personal area network, WPAN) 傳輸技術IEEE 802.15.4因其特性符合短距離、低傳輸速率以及低功率消耗的感測網路之需求，因此成為無線感測網路 (wireless sensor network, WSN) 的主要建構方案之ㄧ。標準的IEEE 802.15.4傳送機制係採用盲目型隨機倒退 (random back-off) 競爭機制以減少電源消耗，然而這項設計並無法滿足在隱藏節點 (hidden-node) 環境中傳輸效能上的需求。尤其是此環境所伴隨而來的隱藏節點碰撞鏈 (hidden-node collision chain) 的情況將導致無法預測的網路效能耗損。遵照此倒退競爭機制，網路裝置之間激烈的競爭過程同樣地會使裝置無法在非隱藏節點環境之中獲得理想的傳輸效能。再者，在集中式管理拓撲(star topology) 下，任兩裝置之間的訊框 (frame) 傳輸皆須藉由協調者 (coordinator) 代為傳遞而加倍消耗網路資源；而在分散式管理拓撲(peer-to-peer topology) 下，任兩訊號範圍內的裝置雖然可以點對點直接傳送訊框，但接收端因為無法預測傳送端何時會提出傳送請求，而得花費許多電力與許久時間在等待傳送端提出請求。上述這些問題都將使得每一筆成功傳送的訊框遭受延遲以及消耗可觀的電力。因此本論文提出一系列新穎的策略以改善上述問題，其中包括：分群 (grouping) 策略、載波多重存取暨碰撞凍結協定 (carrier sense multiple access with collision freeze, CSMA/CF)、晝夜存取 (day and night access, DNA) 機制、以及輪聽策略 (rotational listening strategy, RLS)。分群策略係以犧牲少許網路存取時間而營造一個非隱藏節點的環境並提供顯著的傳輸效能。載波多重存取暨碰撞凍結協定則藉由動態分配專屬的傳輸時間給遭遇隱藏節點碰撞(hidden-node collision) 的裝置以達到減緩隱藏節點環境影響的功效。晝夜存取機制是一種可以改善無線個人網路中裝置間資料交換效能的方案。最後提出的輪聽策略係採用分時多重存取 (time division multiple access, TDMA) 機制與競爭機制兩者混合的概念以避免非隱藏節點環境下碰撞的發生而提供絕佳的傳輸效能。由效能分析與評估後的結果來看，本文所提出的方法策略將可明顯地改善效能、節省電力消耗、縮短存取時間花費並且提升傳輸的成功率。
The emerging IEEE 802.15.4 wireless personal area network (WPAN) is one of solutions for deploying wireless sensor networks (WSNs), wherein applications are restricted by low data rate, short transmission distance and low power consumption. The frame transmission mechanism of the IEEE 802.15.4 standard, which adopts the blind random back-off mechanism, was designed to minimize power consumption. However, it cannot provide satisfactory performance in a realistic hidden-node environment, as it may incur a hidden-node collision chain situation and unexpectedly limit the overall network capacity. Devices with the blind back-off mechanism also cannot obtain ideal transmission performance in a violent contention environment regardless of hidden-node situation. Moreover, transmissions among devices in the same WPAN cost double resources because the WPAN coordinator relays data in the star topology; or receiver would consume much power to wait sender to send a transmission request for the following data transmissions in the peer-to-peer topology. For each successful data transmission, any inefficient transmission mechanism will incur prolonged access delay and consume too much power. As a solution, we propose a series of novel strategies in this dissertation. Strategies include the grouping strategy, the carrier sense multiple access with collision freeze (CSMA/CF) protocol, the day and night access (DNA) scheme and the rotational listening strategy (RLS). The grouping strategy is designed to provide a non-hidden-node environment for devices to obtain notable transmission performance. The CSMA/CF protocol is proposed to alleviate influence of hidden-node situation by dynamically allotting a dedicated time slot for each node suffering from hidden-node collision. The DNA scheme is a novel solution to improve the efficiency of data exchange within a WPAN where data streams may be transmitted from source device to destination device directly or forwarded by the coordinator depending on the hidden-node relationship between sender and receiver. The RLS utilizes both time division multiple access (TDMA) scheme and contention scheme to avoid collisions in a non-hidden-node environment and provide high transmission performance. As confirmed by the results of analyses and performance evaluations, these proposed strategies can achieve significant performance improvement in terms of energy conservation, access delay reduction, and transmission reliability. |
| Appears in Collections: | [電機工程學系暨研究所] 學位論文
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