適用於IEEE 802.15.4協定下高可靠度媒介存取控制層設計

Design of a High-Reliability Medium Access Control Layer for the IEEE 802.15.4 Protocol

李季陽(Chi-Yang Lee)

指導教授 ： 謝志誠

共同指導教授 ： 江昭皚(Joe-Air Jiang)

國立臺灣大學/生物資源暨農學院/生物產業機電工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.01729

摘要

無線感測器網路為近年逐漸被重視的技術，早期常用於生態監測或者環境量測等應用。這些應用普遍不重視資料的可靠度，也對資料封包的傳輸時間沒太大的要求。隨著科技的進步，無線感測器網路的應用逐漸拓展到軍事、醫療照護與工業自動化等領域。在這些應用中，資料的可靠度或封包的傳輸時間常常是有所要求的。
IEEE 802.15.4為常用於無線感測器網路的無線通訊協定之一，但基於早期設計的目的，IEEE 802.15.4協定著重於節能的議題，透過簡化機制與睡眠階段的設置來達到節能的功能。媒介存取控制層為介於實體層與網路層中，其主要功能為安排傳輸媒介的使用，使多個網路設備能在傳輸媒介中有效地進行傳輸。本研究基於IEEE 802.15.4無線通訊協定設計一個媒介存取控制層，在此媒介存取控制層中採用了IEEE 802.11無線通訊協定內所制定的RTS/CTS與重傳兩個機制。利用RTS/CTS機制來克服因為硬體無法有效偵測傳輸媒介所產生的封包碰撞。而重傳機制則能透過重複發送封包的形式來提高封包傳輸的成功率。
本研究實作平台為ADAM-2520Z系列無線感測器節點，使用CC2530無線通訊系統晶片。本研究利用幾項常用於無線感測器網路的評估指標，包括成功率、平均封包傳輸時間與吞吐量來評斷本研究所提出媒介存取控制層性能。透過這幾項指標可以看出本研究所提出的媒介存取控制層相較於IEEE 802.15.4的標準媒介存取控制層能提升1.6倍的資料傳輸成功率以及18.5%的吞吐量，並能減少94.8%的傳輸時間。說明了本研究所提出的媒介存取控制層可以為應用日趨多元的無線感測器網路提供一個高可靠度的傳輸方法。

關鍵字

無線感測器網路 ； 媒介存取控制層 ； 可靠度

並列摘要

Wireless Sensor Networks (WSNs) have become more and more popular these years. At first, the applications of WSNs are focused on ecological monitoring and environmental measurement. These applications do not pay attention to the reliability of monitoring data and transmission time generally. With the advancement of the technology, the applications of WSNs have extended to military surveillance, healthcare, and industrial automation these years. In these kinds of applications, data reliability or transmission time is usually requested.
IEEE 802.15.4 is one of the wireless communication protocols that are commonly used by WSNs. With the initial design, IEEE 802.15.4 focuses on the issue of the energy consumption. IEEE 802.15.4 achieves the goal of energy saving by using a simplified mechanism and the design of a sleeping mode. A Medium Access Control layer (MAC layer) is implemented between the physical layer and network layer. The main task of the MAC layer is to make arrangements for transmission media so that different network devices can operate efficiently via the media. In this paper, a MAC layer that combines an RTS/CTS mechanism is proposed, which uses an IEEE 802.11 wireless communication protocol and includes a retry mechanism. The RTS/CTS mechanism can overcome the defects of failing to accurately detect the media caused by the hardware error. The retry mechanism can increase the delivery ratio by repeating transmitting data packets.
In this paper, the proposed MAC layer is implemented on a wireless sensor node, ADAM-2520Z. The communication module on the ADAM-2520Z uses the CC2530 wireless communication chip. Moreover, some indictors are used to verify the proposed MAC layer. These indictors include the delivery ratio, average transmission time, and throughput. The results show that the proposed MAC layer can increase the delivery ratio by 1.6 times and the throughput by 18.5%, compared to the standard MAC layer defined in the IEEE 802.15.4 wireless communication protocol. In addition, the proposed MAC layer can reduce the transmission time by 94.8%. These findings indicate that the proposed MAC layer can serve as a highly reliable transmission method in multivariate WSN applications.

並列關鍵字

Wireless Sensor Networks (WSNs) ； Medium Access Control Layer (MAC Layer) ； Reliability.

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