SUMMARY

The challenge in the design of energy-efficient medium access protocols for Wireless Sensor Networks (WSNs) is to use the radio only in an “on demand” manner, as the radio transceiver is a major source of WSN energy consumption. Energy-efficient MAC protocols periodically switch the radio transceiver hardware between the costly operation modes receive and transmit, and an energy-saving sleep mode. Most existing power saving MAC approaches synchronize the nodes in the network to let the nodes synchronously wake up at designated instants to exchange pending messages. Synchronization however is expensive and uneasy to achieve. With low traffic, the overhead for maintaining synchronization and slot coordination across a large multi-hop WSN may exceed the energy spent for the actual data. Mechanisms renouncing on synchronization are likely to be more efficient in low-traffic scenarios. We investigate modifications and optimizations on recently proposed fully unsynchronized power saving MAC protocols for wireless sensor networks based on asynchronous wake-up patterns and intended for sensor networks with low traffic requirements.