A real-time MAC protocol for wireless: Virtual TDMA for Sensor (VTS)

Wireless Sensor Network(WSN)are designed for data gathering and processing, with particular requirements and constraints: low hardware complexity, low energy consumption,special trafic pattern suport, scalabity, and in some case, real time operation. In this paper we present the Virtual TDMA foe Sensor (VTS) MAC protocol,which intends to support the previous features, focusing particularly on real-time operation. VTS adaptively creates a TDMA arrangement with a number timeslots equal to the actual number of nodes in range. Thus, VTS archives and optimal throughput performance compared to TDMA protocols with fixed size of frame. The TDMA frame is set up and maintained by a distributed procedure, which allows sensor to asynchronously join and leave the frame. A mayor advantage of VTS is that it guarantees a bounded latency, which allows soft real-time applications. An expression for the upper latency bound is also provided in this paper.VTS performance is evaluated by simulation. Results show less power consumption than other proposals in the field. We also introduce a novel multi-hop operation by cordinated sleep/awake cycles among clusters