DSLR: A Distributed Schedule Length Reduction Algorithm for WSNs

Wireless sensor networks (WSNs) benefit from theMAC protocols that reduce power consumption by avoiding frame collisions. Time Division Multiple Access (TDMA) method provides collision free channel access by employing a pre-defined schedule so that the nodes can transmit at their allotted time slots. Most of the existing distributed TDMA-scheduling techniques for WSNs either try to improve the channel utilization by generating compact schedule which usually takes longer time, or generate schedule quickly, that may not be very efficient in terms of the schedule length. In this paper, we present a new approach to TDMA-scheduling for WSNs, that bridges the gap between these two extreme types of TDMA-scheduling techniques, by providing the flexibility to trade-off the schedule length with the time required to generate the schedule, as per the requirements of the underlying applications and channel conditions. The idea into generate a TDMA-schedule quickly using any of the existing algorithms, and then progressively reduce the TDMA-schedule length. In this context, we provide a distributed schedule length reduction (DSLR) algorithm which can be terminated after the execution of arbitrary number of iterations, and still bereft with a valid schedule. Additionally, unlike other TDMA-scheduling algorithms which use contention-based channel access, the DSLR algorithm uses TDMA-based channel access to perform the schedule reduction. The algorithm has been simulated using the Castalia simulator to compare its performance with those of others in terms of generated schedule length and the time required to generate the TDMA-schedule. Simulation results confirm the effectiveness of the approach, and show that the proposed algorithm generates a compact schedule in much less time in comparison to existing approaches.