適用於IEEE 802.15.4協定下高可靠度媒介存取控制層設計

Abstract

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.