Energy-Conscious Co-scheduling of Tasks and Packets in Wireless Real-Time Environments

Exclusive access to the wireless medium, e.g., as provided by bandwidth-reservation mechanisms, limits contention and therefore is capable of providing effective real-time support to periodic communications. Furthermore, to preserve energy, wireless cards can be powered down between periodic accesses without loss of data. However, packet schedulers must be aware of the limited communication opportunities to ensure that packets are transmitted before their deadlines, CPU schedulers must execute jobs such that the packets generated by these jobs are available for transmission in time, and DVS algorithms must choose processor speeds such that job execution and therefore packet generation are not unduly delayed. This paper proposes a co-scheduling approach to integrate CPU, network, and energy management for wireless real-time systems that rely on bandwidth reservations. Both simulation and experimentation indicate significant improvements in meeting packet deadlines (up to 40%) with only small increases in overall energy consumption (less than 10%) compared to the state of the art.