Energy-efficient adaptive GTS allocation algorithm for IEEE 802.15.4 MAC protocol

The standard IEEE 802.15.4 fails to perform optimally for railway monitoring applications due to the deficiency of guaranteed time slots (GTSs). In the present work, an adaptive GTS allocation algorithm (AGAA) is proposed which efficiently deals with a deficiency of GTSs and slot underutilization problem. The proposed AGAA algorithm saves unutilized bandwidth of GTS and the saved bandwidth is utilized by the needy nodes in contention access period (CAP) and contention-free period (CFP). An independent superframe order (SO_CFP) is introduced for adaptive adjustment of slot size in the CFP. The proposed AGAA protocol also deals with the problem of GTS request-failure due to congestion during CAP. A separate contention period is used for GTS request in AGAA protocol. The comparison has been done between the proposed AGAA protocol and the standard IEEE 802.15.4 medium access control (MAC) protocol. Throughput and energy consumption are analyzed and results show that the slot optimization using SO_CFP saves a fair amount of bandwidth which improves the throughput of the network ≈ 22%. Moreover, the separate contention period for the GTS request frame reduces the idle state energy consumption of those devices which generate time-constraint data frames. The proposed AGAA protocol consumes ≈ 18% less energy than the standard IEEE 802.15.4 MAC protocol. The analysis of results also reveals an important fact that the algorithm saves more energy for homogeneous traffic in comparison to heterogeneous traffic which can further be improved in future works.