Hybrid Zigbee-rfid Networks with Highest Energy Efficiency

Zigbee is the standard of choice in wireless personal area networks with low power consumption, such as, for example, sensor and control wireless networks. Since nodes may be positioned in non-easily accessible places, a high energy efficiency is required in order to maximize the network lifetime and minimize the maintenance costs. A simple and straightforward solution to maximize the network lifetime consists in turning off all nodes which are not needed, e.g., when the node spatial density is higher than that required to satisfy the sensing requirements. We propose an innovative radio-switched Zigbee network, where remote sensor nodes are selectively turned off. More precisely, the radio control is based on the use of Radio Frequency IDentification (RFID) technology, leading to a hybrid Zigbee/RFID architecture. In other words, we consider two logically overlapped networks, RFID and Zigbee. The RFID network turns on/off the nodes of the Zigbee network through a power-off algorithm, referred to as deep sleep algorithm, designed to equalize the residual energy in each Zigbee node. In fact, the RFID controller (i.e., the reader) cyclically switches off the Zigbee nodes with low amounts of residual energy. By building upon the proposed RFID-controlled Zigbee networks, we focus on applications which require a minimum local spatial density of observations. This is of interest, for instance, in distributed monitoring applications, where one needs to monitor the largest possible area in a homogeneous way. In this case, we introduce a virtual spatial grid over the monitored region, and we apply the deep sleep algorithm cell by cell of the grid, requiring that at most one node per cell is active at a time. The proposed hybrid Zigbee/RFID networks are analyzed through Opnet-based simulations.