Advanced GTS Scheduling in IEEE 802.15.4 Networks for Industrial Application

Beacon-enabled IEEE 802.15.4 standard has been widely applied for industrial applications because it can provide contention-free access by using guaranteed time slots (GTSs) in contention-free period (CFP) of a super frame. In IEEE 802.15.4 networks, sensors can also request GTSs for purpose of reliable communication. In existing GTS scheduling studies, however, a sensor wishing to use GTSs has to send a GTS request to a network coordinator. The sending of the GTS request by using carrier sense multiple access with collision avoidance (CSMA/CA) algorithm in fact creates more traffic in the networks. This results in more collisions and packets blocking probability. In addition, if the transmission of GTS request is failed, bandwidth utilization can be low because all GTSs are not allocated. This paper therefore proposes an advanced GTS scheduling (AGS) algorithm, applied in homogeneous networks, to solve those problems. The proposed algorithm eliminates the sending GTS request and allocates GTSs to sensors based on their time order of discovery and the observation of actual allocated GTS usage. Simulation results show that AGS algorithm improves the performance of IEEE 802.15.4 networks in term of bandwidth utilization, packet blocking probability and number of collision per transmission request. In some scenarios, packet blocking probability is reduced about 30 %.