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Lamac: Load Adaptive Ieee 802.15.4 Medium Access Control
Imad H. Elhajj and Wissam Mansour

Medium Access Layer in IEEE 802.15.4 Low Rate Wireless Personal Area Network (LR-WPAN) standard has been an active research area in the past few years. This work aims at enhancing IEEE 802.15.4 network performance through an adaptive algorithm that enables nodes that are allocated transmit GTS (Guaranteed Time Slot) slots within the CFP (Contention Free Period) to redirect CAP (Contention Access Period) traffic to the GTS period in case it is underutilized. The following properties are satisfied by the proposed Load Adaptive IEEE 802.15.4 Medium Access Control (LAMAC): (1) does not increase GTS traffic dropped packets nor delays them significantly, (2) does not affect nodes with only CAP traffic and no GTS allocated, (3) does not increase the delay nor affects nodes pending to be allocated a GTS, (4) does not require changes to the protocol nor affects compliance. To assess the performance of the algorithm, the modified model is simulated over a star topology with several combinations of traffic scenarios. The results obtained revealed the efficiency of the algorithm precisely in low GTS and high CAP traffic scenario where approximately the increase in network throughput is 70% and the decrease in delay is 50%. The results validate the theoretical expressions derived to describe the GTS and CAP traffic required and available bandwidths.

Keywords: Medium access control; IEEE 802.15.4; adaptive; sensor networks; modeling.

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