SMAC-Based WSN Protocol-Current State of the Art, Challenges, and Future Directions

Table 10

Enhanced protocols/algorithms for fixed contention window/poor backoff algorithm.

Reference	Problem	Proposed solution/Purpose	Description	Limitations
[202]	Fixed contention window	An improved SMAC protocol is proposed.	Enhanced SMAC algorithm that adjusts the contention window according to the traffic load in coal mine WSN.	# Localization of mobile sensor nodes in the coal mine tunnels.
[200]	Poor backoff algorithm	Back-off depends on queue and retry (BDQR)	BDQR improve on the original backoff algorithm of SMAC by introducing a failure counter (Fcounter), q variable, and a disjunctive window threshold (CWm).	# The experimental results that reduced channel collision and improved node communication fairness were not clearly explained.
[64]	Fixed contention window/backoff algorithm	R-MAC in MAC layer	Combines adaptive contention window and forecasting data flow based on SMAC’s nodes length of the queue.	# The algorithm for the protocol design is not given.
				# Unequal performance metrics for both star and mesh topological scenarios.
[201]	Fixed contention window	ACW-MAC protocol	Adjusts the SMAC contention window using self-adaptive and neighbour competition of the channel in conjunction with the MIMLD algorithm.	# Priority of packet transmission and topological changes.
[68]	Poor backoff algorithm	Adaptive back-off and duty cycle for SMAC (ABDC-SMAC)	The flow factor measures network traffic and dynamically changes the duty cycle for improved energy consumption and transmission delay.	The duty cycle is not varied.