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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 low latency deterministic networked control systems. Each end device in network transmits its data frame after certain time delay in response to periodic request from network coordinator. This time delay 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 modifications reduces the non-determinism of the network and increases its bandwidth efficiency. Experiments were conducted to evaluate the suggested protocol. Based upon these experiments results, the proposed protocol is a feasible solution for control systems with real time constraints.

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.