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In a cyber physical system like vehicles number of signals to be communicated in a network system has an increasing trend. More and more mechanical and hydraulic parts are replaced by electronic control units and infotainment and multimedia applications has increased in vehicles. Safety critical hard real time messages and aperiodic messages communicated between electronic control units have been increased in recent times. Flexray is a high bandwidth protocol consisting of static segment for supporting hard real time messages and a dynamic segment for transmitting soft and non real time messages. In this paper, a method to obtain the stability region for the random arrival of messages in each electronic control units which is scheduled in the dynamic segment of Flexray protocol is presented. Number of mini slots available in the dynamic segment of Flexray restricts the arrival rate of tasks to the micro controllers or the number of micro controllers connected to the Flexray bus. Stability region of mathematical model of the system is compared with the Flexray protocol simulation results. [ABSTRACT FROM PUBLISHER]

In a real time system, processor time is sometimes wasted on jobs that have no chance of being completed before their respective deadlines. Such wastage may be avoided by routinely discarding such jobs at the epoch of their getting the server. However, this modification, which is referred to in this paper as the Early job Discarding Technique (EDT), makes the scheduling policy dependent on service time. As a result, the optimality of the Earliest Deadline First (EDF) scheduling policy becomes inapplicable. We show in this paper that the said modification preserves the superiority of the EDF over the First Come First Serve (FCFS) scheduling policy in terms of loss ratio. Results of Monte Carlo simulations indicate that the gap between the loss ratios of the two scheduling policies under EDT widens with higher arrival rate. [ABSTRACT FROM AUTHOR]

In this paper, we prove that the loss ratio of a G/G/1/G system with deadline till the end of service, operating under the EDF scheduling policy with preemption, can only be reduced by using an Exact Admission Controller. On the other hand, for a G/M/1/G system, this reduction is less than that arising from a simple modification of the EDF scheduling policy, where a job about to get the server is automatically discarded if it is found at that time that it cannot meet the deadline. Results of Monte Carlo simulations suggest that this modification produces substantial reduction of the loss ratio when the arrival rate is high, but the Exact Admission Controller is able to achieve comparable reduction of the loss ratio in this situation only if the mean relative deadline is large. [ABSTRACT FROM AUTHOR]