TDMA based IEEE 802.15.4 for simple/secured low latency deterministic networked control systems

In this paper, we propose a time division multiple access (TDMA) based protocol that works on slightly modified IEEE 802.15.4 network in star topology for secured and unsecured low latency deterministic networks (LLDN) for industrial control systems. This protocol ensures total superframe time as low as ten milliseconds as compared to minimum possible superframe time of 15.36 milliseconds. In these networks, Each end device transmits its data frame in their allotted timeslot. The timeslot and inter timeslot spacing is optimized for channel bandwidth utilization and reliable data frame exchange. While this TDMA based protocol eliminates the risk of frame collisions to great extent, MAC sub-layer tweaking improves the non-determinism of the network and increases its bandwidth efficiency. We also investigate the security impact on the performance of LLDN. A mathematical model is developed that takes empirical values as input and predicts the worst case arrival times of network devices at coordinator. Experiments were conducted to evaluate the suggested protocol and mathematical model.