Power Aware Scheduling for ADHOC Sensor Network Nodes

Abstract

Adhoc Sensor Networks are being considered for many novel applications. This thesis investigates into the power aware scheduling aspects of adhoc sensor networks with a real time test-bed environment. This will include the Periodic and Aperiodic Task Scheduling Issues, as well as power consumption by sensor nodes.

The architecture configured for the project work has been put forward with intricately defined requirements for each component. Texas Instruments’ low power microprocessor, MSP430 is used to implement Modified Maximum Urgency First (MMUF), priority based scheduling algorithm to schedule periodic and aperiodic tasks generated by the MicroC/OS-II operating system or interrupt received by the MSP430. Aperi-odic tasks always given higher priority compare to periodic tasks. The scheduler is configured to run on the MicroC/OS-II Real Time Operating System (RTOS). Out of the two Real Time Operating Systems for sensors (TinyOS and MicroC/OS-II), which were studied, MicroC/OS-II was selected for the project work, due to its ex-tensibility, robustness and priority scheduling. Out of the _ve scheduling algorithms (RM, EDF, MLF, MUF and MMUF), which were studied, MMUF was selected for the project work, because it doesn't allow critical task to miss deadline. As com-pared to conventional Real Time Operating Systems for sensors, which are generally not open systems, MicroC/OS-II can be used as an Operating System for sensors and can be extended to implement new scheduling algorithms, which can be integrated and tested in real time working environment.

Another aspect of the project work is user priority based scheduling of the tasks. This is because; the Adhoc Sensor Network based Applications must adhere to strin-gent real-time constraints and Power Aware requirements. Therefore, a user priority based, Modified Maximum Urgency First (MMUF) is developed to orchestrate and guarantee the timely interaction between such applications. In this context, a kernel level module is developed to switch the MSP430 into Low Power Mode (LPM) to reduce the power consumption by the sensors, when no user task is active.