Energy Consumption Analysis of ZigBee-Based Energy Harvesting Wireless Sensor Networks Jiaying Song and Yen Kheng Tan Energy Research Institute Nanyang Technological University, Singapore 637553 {jysong, tanyk}@ntu.edu.sg Abstract —Energy consumption is one of the most important practical properties for deploying an energy harvesting wireless sensor network. This paper presents the energy consumption analysis of ZigBee-based energy harvesting wireless sensor networks to understand the energy requirements to the energy harvesting technologies from a practical aspect. Three kinds of energy consumption are analyzed to investigate the main factors influencing the design of energy harvesting technology: the energy consumption of end devices and of routers in power up mode, the energy consumption of data transmission with/without application acknowledgement requirements, and the energy consumption of routers supporting different node density. Based on the measurements, the key metrics influencing the lifetime of wireless sensor networks are summarized and an energy consumption model is proposed to evaluate the lifetime of a sensor node. Moreover, the potential energy-saving solutions are discussed for ZigBee-based energy harvesting wireless sensor networks. Keywords-wireless sensor networks; ZigBee; energy consumption measurement; energy harvesting I. I NTRODUCTION ZigBee is a network and application layer specification for low-power radio devices based on IEEE 802.15.4 standards. It has been widely used in the deployment of wireless sensor networks. Due to the mesh networking, ZigBee can provide high reliability and extensive range for wireless sensor networks. Therefore, it gains much attention both in commercial and academic area. Energy harvesting technologies are expected to provide stable energy for wireless sensor networks. An energy harvester converts various types of environmental energy into electricity and stores the energy to be applied to a sensor node. However, since the energy-producing rate at the harvester is limited, the energy consumption analysis plays an important role to the capacity design of energy harvesting technologies [1]. In addition, energy consumption is also the most critical metric influencing the lifetime of wireless sensor networks [2]. The theoretical energy or power consumption models are useful to simulate the performance of wireless sensor networks while having little contribution to real application [3]-[5]. Recently, several energy consumption measurements have proposed. In [6], the total en ergy consumption of a senso r node is measured by the CC1000 integrated radio circuit. In [7], J. Alonso et al have investigated the main parameters including duty cycles, data processing and wireless data transmission power and data sensing power using ZigBee EM2420 RF module. In [8], the energy consumption of sensor nodes in transmission and receiving mode is experimented via CC2420. Unfortunately, there are still other parameters need to be considered. 1) Energy consumption in power up mode. When the sensor nodes or routers power up, they needs high energy in a short period. That is critical for designing the energy havesting part for the wireless sensor network. 2) Energy con sumption of reporting data with application acknowledgement requirements. In some critical monitoring applications, the sensor nodes need to make sure the coordinator or the access point receives the packets correctly. Other than the media access control (MAC) layer acknowledgement that can only indicate the receive status of the raw MAC packet, ZigBee specifies the application layer acknowledgement to help a sensor node know whether the packets it sent was received by the coordinator without any error. But the sensor node needs to set its status idle and to wait for dozens of or hundreds of milliseconds before requesting application acknowledgement. The waiting process consumes much energy and shorts the whole network lifetime. 3) Energy consumption of routers. A ZigBee-based wireless sensor network consists of a coordinator served as the gateway or the sink node, several routers and lots of end devices (i.e. sensor nodes). The connectivity of the network is maintained by the multi-hop communications among the routers and each sensor node is connected to a router via one- hop transmission, which means if a router runs out of power, many sensors may be unable to report data to the coordinator. As a consequence, like the energy consumption of sensor nodes, the routers’ energy consumption also determines the lifetime of the network. In this paper, we measure the energy consumption in ZigBee-based energy harvesting wireless sensor networks. The energy consumptions in power up mode, of reporting data with and without application acknowledgement, and of routers are experimented. Especially, the influence of node density on routers’ energy consumption is experimented. Furthermore, 978-1-4673-2054-2/12/$31.00 ©2012 IEEE 468
