Energy efficient and QoS aware medium access control for wireless sensor networks

Enabling quality of service (QoS) applications over battery-constrained wireless sensor networks (WSNs) poses significant challenges, because of the special characteristics of such networks. Developing real-time applications for WSNs necessitates the development of new communication protocols capable of achieving application-specific QoS and at the same time save energy. In this paper, we continue our previous work on developing and improving our EQ-MAC protocol, which is designed specifically for WSNs to reduce energy consumption and provides QoS guarantees through the use of the service differentiation concept. The proposed protocol consists of two subprotocols: Classifier MAC (C-MAC) and Channel Access MAC (CA-MAC). C-MAC is responsible of classifying gathered data at sensor nodes based on its importance. The CA-MAC is an energy conserving medium access mechanism which uses a hybrid scheduling technique. CA-MAC saves energy by differentiating between control and data messages. Data messages are assigned scheduled slots with no contention (here we have to emphasize that slots are assigned only to those nodes that have data to send, this allows an efficient energy use of the Time Division Multiple Access (TDMA) slots), whereas short periodic control messages are assigned random access slots. To study the performance of the EQ-MAC protocol, we have conducted several simulation experiments on Network Simulator (NS-2) to evaluate and compare the performance of our protocol against S-MAC and Q-MAC protocols. Simulation results demonstrate that EQ-MAC outperforms the other two protocols and achieves a significant improvement in terms of the energy expenditure and delivery ratio. Under prioritized traffic, EQ-MAC is comparable to Q-MAC in average latency, while achieving less energy consumption. Copyright (C) 2010 John Wiley & Sons, Ltd.