No abstract

Wireless Sensor Networks (WSNs) are receiving an ever increasing attention because they are one of the most important technologies enabling the Internet of Things vision. Since nodes of these networks are battery-powered, energy efficiency represents one of the main design objectives. This goal can be primarily achieved through an optimization of the communication phase, which is the most power consuming operation for a WSN node. However, the limited computational and storage resources of physical devices make the design of complex communication protocols particularly hard, suggesting, on the contrary, to integrate more simple communication protocols with hardware solutions aimed at energy saving. In this work, a new MAC protocol, compatible with the IEEE 802.15.4 standard, and a reconfigurable beam-steering antenna are presented and validated. They significantly reduce the nodes’ power consumption by exploiting scheduling techniques and directional communications. Specifically, both during transmission and receiving phases, the node activates exclusively the antenna sector needed to communicate with the intended neighbour. The designed antenna and the proposed protocol have been thoroughly evaluated by means of simulations and test-beds, which have highlighted their good performance. In particular, the MAC protocol has been implemented on the Contiki Operating System and it was compared with the IEEE 802.15.4 standard solution.

Abstract-Directional and switched-beam antennas in wireless sensor networks are becoming increasingly appealing due to the possibility to reduce transmission power and consequently extend sensor node lifetime. In this work, a reconfigurable beam-steering antenna is proposed for Wireless Sensor Network applications in the ISM band (f = 2.4-2.4835 GHz). The proposed radiating structure consists of a vertical half-wavelength dipole antenna and eight microstrip antennas composed of a rectangular two-element patch antenna array. These microstrip antennas have a directional radiation pattern in the azimuth plane with a HPBW of nearly 60 degrees. A control circuit consisting of a transmission line, RF-switches and a 4 : 16 multiplexer has been designed in order to dynamically switch among nine radiation patterns, eight directional and one omnidirectional. Simulations and experimental results, referred to a low-cost realization on a FR4 substrate with a thickness of 1.6 mm, demonstrate appreciable performance.