International audienceIndiscriminated packet discards strongly degrade the quality perceived by end users of MPEG video transmissions. This paper investigates different Quality of Service (QoS) schemes and the tradeoffs of jointly adopting such schemes to improve the delivery quality of an MPEG stream. From an analytical model, we evaluate the impact of frame losses on the quality of MPEG streams and on the waste of network resources. Our assessment considers issues such as the use of redundancy by applying a Forward Error Correction (FEC) scheme to tolerate losses, the changing of the compression factor in MPEG encoding, the unequal protection of MPEG frames in a Differentiated Services environment, and how to evaluate the impact of network losses onto application quality. Results provide predicted bounds on the quality to be expected by end users as well as guidelines on how to take the best advantage from the joint adoption of the investigated QoS schemes

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Wireless Sensor Networks (WSNs) are distributed systems whose main goal is to collect and deliver data to applications. This paper proposes a reflective, service-oriented middleware for WSN. The middleware provides an abstraction layer between applications and the underlying network infrastructure and it also keeps the balance between application QoS requirements and the network lifetime. It monitors both network and application execution states, performing a network adaptation whenever it is needed. Simulation results show that the network residual energy can be increased in more than 100% when adopting an adaptation strategy, while the application QoS requirement is respected.

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