Issues on convergecast scheduling in Industrial Wireless Sensor Networks

Industrial Wireless Sensor Networks (IWSNs) consist of a central manager, gateways and field devices with sensing, signal processing and wireless communication capabilities. Convergecast is a many-to-one industrial communication paradigm which is used for process measurement and control applications. Convergecast scheduling in IWSNs is to determine the smallest length conflict-free assignment of timeslots during which the packets generated at each node reach the central manager. The transmissions are scheduled based not only on the network topology, but also on the interference graph due to the broadcast nature of wireless transmissions. In this article we present issues on convergecast scheduling. We first outline the design models for convergecast scheduling followed by a comprehensive study of scheduling algorithms. Overall, the convergecast scheduling algorithms are classified based on the network management method into two categories: centralized and distributed scheduling. Furthermore, these scheduling algorithms are classified into raw-data convergecast and aggregated convergecast. Finally these scheduling algorithms are also classified into collision-free scheduling and spatial-reuse scheduling.