EFFICIENT BROADCASTING METHOD OF SCHEDULE TABLE FOR A CENTRALIZED SCHEDULING ALGORITHM IN IEEE802.15.4E TSCH

Abstract

Communication over wireless medium has an important place in the considerably evolving world of technology. In almost every field of life, wireless technologies have a significant ground which rises a variety of interesting applications such as in the industrial area. That because the wireless network offer benefits such as weight reduction, freedom from wires, flexibility and ease in maintaining the system. Those benefits can be seen in real world like environmental monitoring, smart home and many others. It exists different type of wireless technology used in the Internet of Things. Apart the Bluetooth, WI-FI and GSM, the IEEE 802.15.4e Time Slotted Channel Hopping (TSCH) as MAC protocol, is an important standard in the actual scalable Internet of Things (IoT) to habilitate deterministic low-power mesh networking. Wireless Sensor Network (WSN) are indispensable and once deployed in industrial applications, they require deterministic and tight latencies in scheduling. Scheduling in TSCH can be centralized or distributed. In Centralized scheduling, the central entity or coordinator, computes and assigns the communications resources like timeslot and channel to all nodes based on a certain scheme or algorithm. At the end, that schedule table needs to be known by each node in the network. Our work describes an efficient method to broadcast a schedule table in TSCH centralized scheduling in a global environment where IPv6 devices meet the Wireless Sensor Network through the 6LBR implemented in Raspberry Pi which works also as a scheduling server. We chose to make a schedule table by implementing a centralized link scheduling for IEEE 802.15.4e TSCH based industrial Low Power Wireless Networks, known as Path Conflict free Least Laxity First (PC-LLF) algorithm [10] in Contiki OS, a real time operating system for wireless sensor. We ensure that all data transmissions are done exactly as assigned in schedules by implementing a method to broadcast the schedule table information packets to all transmissions generator (nodes) with the aim to reduce packets collision and loss. We compared the number of packets messages needed to deliver to all nodes the schedule table information when using our method and when using other method such as CoAP and OCARI broadcasting method which is a custom-made method. The implementation takes in consideration the use of RPL protocol for network topology construction. The used hardware devices are Texas instruments CC 2650 Launchpad.