We present the design of a multicore version of FreeRTOS, a popular open source real-time operating system for embedded applications. We generalize the scheduling policy of FreeRTOS to schedule the n highest-priority longest-waiting tasks, for an n-core processsor. We use a locking mechanism that provides maximum decoupling between tasks, while ensuring mutually exclusive access to kernel data-structures. We provide an implementation of the portable part of FreeRTOS (written in C) and provide the device specific implementation of the locking mechanism for Intel and ARM Cortex multicore processors. We model the locking mechanism and the locking protocol used by the API's in the Spin model-checking tool and verify that the design is free from dataraces and deadlocks. Finally, we extend the existing FreeRTOS Windows simulator to simulate our multicore version of FreeRTOS, and evaluate its performance on some demo applications.

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Communication establishment is crucial for rescue operations in disaster affected areas. A standard tool for communication is the use of cell phones. However, they can be useless in situations where the cellular network’s base stations are damaged in a disaster. A contemporary approach to re-establishing a communication network is by hosting base stations in drones. However, low battery life and difficulty in calculating the number of drones needed in different terrains are limitations of the above approach. This paper introduces a novel terrain-aware algorithm that calculates the minimum number of drones needed to cover an area with no voids in the network coverage. Our method ensures that the drones are deployed at optimal heights to maximize the average leftover energy in the network. We apply the algorithm for an actual location in Pettimudi, India and find the optimal number and positions of the drones to cover the area effectively without voids. In addition, we provide a simulation of the the communication establishment using above drones, and our experiments yield an average network efficiency of 98%, showing the effectiveness of our method.

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