Affiliation:
1. Arab Open University, Lebanon
Abstract
Wireless sensor networks consisting of several sensors deployed in a given area, under an internet of things (IoT) paradigm, are considered. Sensor nodes may or may not be close enough to communicate with each other in order to perform collaborative transmissions. A communication protocol based on random access and orthogonal frequency division multiple access (OFDMA) is proposed in order to allow the sensors to operate autonomously by transmitting their measured data to a central processing system, where it is processed and analyzed. Whenever it has data to transmit, each sensor independently accesses a time-frequency slot in a probabilistic manner to avoid collisions. A controlling entity, e.g., a central base station (BS) covering a certain sensor deployment area receives the sensor transmissions and provides synchronization information by periodically transmitting a pilot signal over the available OFDMA subcarriers. Sensors use this signal for channel quality estimation. Results show that this approach performs well in terms of transmission data rates and collision probability.