Radio Frequency/free Space Optical Research Articles

Hybrid Radio and Optical Communications for Energy-efficient Wireless Sensor Networks

A wireless sensor network (WSN) consists of a large number of networked sensor nodes deployed to sense and report a particular phenomenon to a base station. One of the main design considerations for WSNs is the energy consumption of the individual sensor nodes. Currently, most WSNs are radio frequency (RF) based, and communications account for a significant portion of the energy expended. The hybrid radio frequency/free space optical (RF/FSO) WSN is proposed to lower energy consumption. The RF and FSO link models used for the RF/FSO WSN are first discussed. Next, the energy expended by the sensor nodes for sensing, data processing and communications is modeled. These models are used to simulate the lifetime of the WSN. To investigate the energy efficiency of the RF/FSO WSN, an RF-only WSN is used for comparison. Simulations show that the average energy consumed by the nodes in the RF/FSO network is significantly lower than that of the RF-only network, thus increasing the lifetime of traditional RF-based WSNs.

Radio Frequency/Free Space Optical and Radio Frequency-only Wireless Sensor Networks: A Comparative Study of Performance

Wireless sensor networks (WSNs) consist of networked sensor nodes, deployed to sense a phenomenon and report it to a base station. Sensor nodes are small and usually equipped with small batteries with limited capacity, and therefore, one of the most important design considerations for WSNs is power consumption. WSNs expend energy for communications, data processing and sensing; for commonly used RF communications this task accounts for the largest portion of power expended. Hybrid radio frequency/free space optical (RF/FSO) communications has been proposed to reduce power consumption by the sensor node, and in this paper, the performance of the RF/FSO WSN is compared against an RF-only WSN in terms of network lifetime and coverage. Results show that for the wide range of scenarios considered, the RF/FSO WSN lasts at least twice as long as its RF-only counterpart, despite providing the same level of network coverage. This paper also investigates network parameter selection for optimum RF/FSO network coverage.