An Improved MAC Protocol for Wireless Sensor Networks in Medical Application
Wei Zhao, Shi Gang · Applied Mechanics and Materials · 2012
Wireless Sensor Networks (WSNs) provide a valuable capability to autonomously monitor remote activities. Their limited resources challenge WSN medium access control (MAC) layer designers to adequately support network services while conserving limited battery power. 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. This paper proposes M-MAC, a medium access control protocol designed for medical wireless sensor networks. M-MAC’s centre management function offers significant energy savings by wiping off contention and keeping nodes sleeping all the time except awaking to send its Data package. All Slave Node(SN) need only communicate with a specific Master Node(MN) in a group and due to close range, routing is unnecessary. The MN acts as scheduler and when receives a Data package from a SN, it will indicate the SN how long it should be asleep and what it should do after awaking. Period is introduced as the time windows and it is divided into Frame Time. Every MN occupies a unique Frame Time and this is decided by its MAC address. Then the Frame Time separates into smaller Slot Time and it is the atomic time span for SN exchanging data with MN. Practice has proved that the M-MAC protocol is effective in our medical application and it can extend the lifetime of SN greatly