Protocol for improved energy efficiency in wireless sensor networks to support mobile robots

In this paper we propose a low cost and computationally inexpensive adaptive transmission power control algorithm for wireless sensors to communicate with the base station or hub. This power control algorithm can be used in scenarios where the transmitting station is not static and the distance between the transmitter and the receiving station changes with time. In addition to that there can be unwanted obstructions in between the transmitter and the receiver. Since the primary reason for drop in received signal strength is distance, it is important to select a set of power levels that will deliver the packets within a threshold error rate while saving energy. This adaptive algorithm does not use received signal strength indicator (RSSI) based beacon or probe packet for channel estimation nor listens for any busy channel before actual packet transmission. The hardware used for evaluating the protocol parameters is nRF24L01+ transceiver module from Nordic Semiconductor Inc. This chip is extremely cheap and the application of the adaptive power control protocol can reduce the overall deployment cost of sensor network. This algorithm is designed to meet the challenge of responding to an unknown and variable radio channel in an energy-efficient manner. The adaptive protocol uses past transmission experience or memory to decide the power level at which the new packet transmission will start. This lightweight protocol can be applied in mobile robots that collect data in real time from sensors and transmit to the base station.