Flexible online multi-objective optimization framework for ISA100.11a standard in beacon-enabled CSMA/CA mode

Maintaining high quality of service (QoS) for sensor nodes is important in industrial wireless sensor networks (IWSNs). Wide range of factors severely affects QoS; The PDR is assumed to be our measure for QoS. A user defined grouping scheme for ISA100.11a (UDG-ISA100.11a) is developed assuming that nodes are grouped with an assigned level of QoS. The user is granted high flexibility to achieve a required QoS level with desired number of nodes. The objective function is formulated to maintain a high number of node and the least difference from the desired weighting ratio in the groups. In this article, nodes are predominantly grouped based on their QoS requirements and then optimized in online mode using a constrained genetic based multi-objective approach. The proposed framework is termed as a flexible online multi-objective optimization (FOMOF) to maintain a minimum desired QoS of the pre-determined groups with maximum number of nodes. Furthermore, the packet delivery ratio (PDR) obtained from the FOMOF was higher than the one obtained by ISA100.11a standard. Accordingly, the grouping strategy enhanced the number of nodes by 12.5% with End-to-End delay reduction of 16.36% for 27 nodes. The results revealed that a good tracking to the desired level of QoS with less average E2E Delay and a maximum number of nodes has been achieved. Another result has shown that the highest number of total nodes in the network enhanced the delay of packet delivery. It is established that all QoS relevant number of nodes in the system can be arranged to attain the desired QoS. 78