In recent integrated MAC/routing solutions for wireless sensor networks (WSNs), hop-count is exploited to build a coarse-grained logical coordinates to help forward packets towards the direction of sink. This method can retain the merits of geographic routing at the absence of exact location knowledge. However, these solutions may present low energy-efficiency and unacceptable delays in real networks since they seldom consider the impacts of low duty-cycling and link unreliability on routing. Furthermore, geographic advancement of forwarding in hop-count based coordinates is very unreliable and even towards the reverse direction. In this work, average power cost to the sink of each node is considered together with hop-count to build a fine-grained logical coordinates, which can help forward packets towards the direction of sink more accurately. Then we propose an energy-efficient integrated MAC/routing (EEMR) protocol for event-driven and time-critical applications based on new logical coordinates. The optimal relay is elected in each hop dynamically, where the objective is to optimize forwarding energy-efficiency on the premise that end-to-end delay is restricted under the predefined upper bound. Analysis and extensive simulations are given to demonstrate the superiority of EEMR by comparing its performance against existing solutions.
['Xinguo Wang', 'Xinming Zhang', 'Qian Zhang', 'Guoliang Chen']
An Energy-Efficient Integrated MAC and Routing Protocol for Wireless Sensor Networks