Hybrid RF/optical wireless networks

One of the main design considerations for wireless sensor networks (WSNs) is the energy consumption of individual sensor nodes. Currently, most WSNs use radio frequency (RF) channels for communications, and this accounts for a significant portion of the energy expended. Free space optical (FSO) communications can be used where a line of sight exists between a sensor node and an optical 'base station', as we have demonstrated in work on communications with micro-machines. This requires very little energy use at the sensor node, but does require a line of sight between sensors and the base station. Using a combination of RF and FSO links allows communications using FSO where there is a line of sight, and RF where there is not. Analysis shows that this hybrid network can have significantly lower energy consumption, and hence longer lifetime than an RF only example.