Redesign of Probability Distribution to Select Contention Slot in MAC protocol for Real-Time Wireless Sensor Network
Ho Jang, Ho-Youl Jung, Ki-Dong Lee · ICEIC : International Conference on Electronics, Informations and Communications · 2008
Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad-hoc method of deployment. Several research papers have been focused on overcoming these deficiencies through faster media accessing, more energy efficient routing, localization algorithms and system design. But, traditional carrier sense multiple access with collision avoidance (CSMA/CA) protocols like IEEE 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size. Our research attempts to provide a method of improvement MAC performance in these issues. We present effective method of accessing to medium in real-time wireless sensor networks. Proposed MAC protocol is a randomized CSMA protocol, but unlike previous legacy protocols, does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, it carefully decides a fixed-size contention window, non-uniform probability distribution of transmitting in each slot within the contention window. We show that it can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely used simulator ns-2. We finally show that proposed MAC scheme comes close to meeting bounds on the best latency achievable by a decentralized CSMAbased MAC protocol for real-time wireless sensor networks which is sensitive to latency.