To conserve energy, periodic active/sleep dynamics is adopted in wireless sensor networks. At the same time, the QoS guarantees, such as packet delay, packet loss ratio and network throughput need to be satisfied. We develop a finite queuing model for sensor nodes and derive network performance for contention-based wireless sensor networks with synchronous wakeup patterns. Furthermore, the impact of active/sleep duty cycle, time scale and node buffer size on the tradeoff between energy efficiency and QoS guarantees is studied based on the model. Simulation results well match our analytical results and validate the accuracy of our model and approach.

In this letter, we propose a new energy efficient online routing algorithm for QoS-sensitive sensor networks. An important design principle underlying our algorithm is online decision making based on real time network estimation. This on-line approach gives adaptability and flexibility to solve a wide range of control tasks for efficient network performance. In addition, our distributed control paradigm is practical for real sensor network management. Simulation results indicate the superior performance of our algorithm between energy efficiency and QoS provisioning.

In this paper, we propose flow aggregation algorithms for multicast video transport. Because of heterogeneities of network/client environments and users' preference on the perceived video quality, various QoS requirements must be simultaneously guaranteed even for the single video source in the multicast connection. It is easy but ineffective to provide many video streams according to each user's request. Our flow aggregation algorithm arranges similar QoS requirements of clients into a single QoS requirement, by which the required number of video streams that the video server prepares can be decreased. Then the total amount of the required bandwidth can be reduced by sharing the same video stream among a number of clients. Our flow aggregation algorithm has two variants, which are suitable to sender-initiated and receiver-initiated multicast connections, respectively. Proposed algorithms are evaluated and compared through simulation. Then we show that the server-initiated flow aggregation (an ideal case in our approach) is most effective, but the receiver-initiated flow aggregation can also offer a reasonably effective mechanism.

In this paper an ATM call level model, where service classes with QoS guarantees (CBR/VBR) as well as elastic (best effort) services (ABR/UBR) coexist, is proposed and a number of simulations have been carried out on three different network topologies. Elastic traffic gives on the network level rise to new challenging problems since for a given elastic connection the bottleneck link determines the available bandwidth and thereby put constraints on bandwidth at other links. Thereby bandwidth allocation at call arrivals but also bandwidth reallocation at call departure becomes, together with routing, an important issue for investigation. Two series of simulations have been carried out where three different routing schemes have been evaluated together with two bandwidth allocation algorithms. The results indicate that the choice of routing algorithm is load dependent and in a large range the shortest path algorithm properly adopted to the mixed CBR/ABR environment performs very well.