| Summary: | 碩士 === 元智大學 === 電機工程學系 === 106 === ABSTRACT
Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals.
The duty-cycle MAC protocol like S-MAC has been proposed to meet the demanding energy requirements of wireless sensor networks. S-MAC lets nodes periodically sleep to reduce energy consumption. Moreover, R-MAC is another duty-cycle MAC that can save energy like S-MAC, but it improves the throughput of S-MAC by using a setup control frame that can travel across multiple hops and schedule the upcoming data packet delivery along the route. Whereas the common shortcoming of R-MAC and S-MAC is that they use the IEEE 802.11 distributed coordination function in their control slot, which achieves only limited performance because of the considerable idle time and the high rate of transmission collisions caused by the back off procedure at high loads.
Therefore, in this paper, we propose a distributed dynamic reservation MAC scheme, which aims at ensuring low control overheads and collision-free data transmission to maximize system performance without sacrificing energy efficiency. Our scheme provides the reservation phase, which lets the node reserves at his scheduled time if he has data to send, and further provides inform phase to let everyone know their priority order in order to achieve collision-free data transmission and better spatial reuse. The simulation results demonstrate that the proposed MAC scheme achieves better system performance than R-MAC under a wide range of traffic loads and also achieves significant improvement in end-to-end delivery latency over R-MAC.
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