Long battery life and high performance multimedia decoding are competing design goals for portable appliances. For a target level of QoS, the achievable battery life can be increased by dynamically adjusting the supply voltage throughout execution. In this paper, an efficient offline scheduling algorithm is proposed for preprocessing stored MPEG audio and video streams. It computes the order and voltage settings at which the appliance's CPU decodes the frames, reducing energy consumption without violating timing or buffering constraints. Our experimental results elucidate the trade-off between QoS and energy consumption. They demonstrate that the scheduler reduces CPU energy consumption by 19%, without any sacrifice of quality, and by nearly 50%, with only slightly reduced quality. The results also evaluate how the QoS/energy trade-off is affected by buffering and processor speed.

In today's multicomputers, software overhead dominates the message-passing latency cost. We designed two multicomputer network interfaces that signif~cantiy reduce this overhead. Both support vMual-memory-mapped communication, allowing user processes to communicate without expensive buffer management and without making system calls across the protection boundary separating user processes from the operating system kerneL Here we compare the two interfaces and discuss the performance trade-offs between them.

Abstract. RFID reader networks often have to operate in frequency and time constrained regimes. One approach to the allocation of frequency and time to various readers in such regimes is to perturb the network slightly so as to ease the constraints. We investigate how to perform these perturbations in a manner that is profitable from time and frequency allocation point of view.

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