A MAC protocol for real-time sensing applications using asymmetric transceivers

We consider a class of single hop wireless sensor networks in which the sensor nodes collect data periodically and transmit it to a sink. To reduce the complexity, cost and energy consumption of the nodes we propose the use of an asymmetric transceiver model in which the sensor nodes can transmit to the sink using standard physical layer modulation schemes that support relatively high data rates but can receive from the sink using basic modulation schemes that can only support very low data rates. The use of the transceiver module in each sensor node is thus limited to receiving simple feedback in the form of a few bytes of ACK from the sink node. In this paper we propose and study a new MAC protocol that enables effective communication between the sensor nodes and sink in such a network. We develop an analytical model to evaluate the performance of the MAC protocol and verify these results through extensive simulations. We also present results from the implementation of the protocol on a test bed consisting of XSM motes and evaluate its performance in a real world scenario.