ITR: Collaborative Research: Optimization and Integrated Control of Low Power Wireless Multimedia Networks

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Recent years have seen an explosive growth in the number of multimedia devices and communication tech-nologies. While these multimedia technologies still depend on wireline links, the future of multimedia com-munication is in wireless. Mobile multimedia networks will provide seamless communication between roam-ing users. Applications such as video conferencing or internet access will become available from any where in the world. Widely varying classes of network traffic (traffic heterogeneity) that change over time will be generated by multimedia applications. The network itself will consist of both wireline and wireless links (network heterogeneity). We are already beginning to feel this change.A major constraint in multimedia wireless technology is the limited power budget. Mobile devices such as laptops and personal digital assistants have limited battery life. The re-chargeable battery technology has resulted only in a small increase in battery efficiency. So, it is important to optimize network protocols for minimum power to ensure the continued growth of wireless based multimedia communication. Many attempts have been made towards this goal at individual layers of the network protocol stack. Most of these efforts have concentrated only at the physical and link layers. In this proposal, we deal with the wireless network protocol stack as a whole and provide a unified framework to optimize both computation and transmission power at various layers of the protocol stack. A power manager serves as the central core of our framework. Thedifferent layers of the protocol stack communicate with each other through the power manager that makes adaptive policy decisions based on the network, traffic, and power limitations. This is a uniqueness of the proposal. In the conventional model, the network layers have minimal or no communication at all leading to poor performance compared to the proposed framework. The proposed methods strive to optimize the quality of service (QoS) with minimum power consumption at the mobile wireless nodes. Towards achieving our objectives we consider the following research issues :Adaptive source coding and modulation strategies at the physical layer that minimize power for a desired reliability. The adaptation is done based on channel state estimates produced by the link layer.New error-resilient coding methods that do not have the drawbacks of the conventional forward error correcting codes. Little overhead, graceful degradation, and simple encoding and decoding that reduce the power requirements for computations are the main strengths of the coder. The coders are especially well-suited for state-of-the-art compression standards like JPEG, MPEG, and H.263. Radically different on-line channel state estimators are also proposed.Power-aware transport control protocols that distinguish between various channel and battery state.Application layer adaptation mechanisms to conserve power. The mechanisms use techniques from networking and signal processing areas to improve the performance.Adaptive power manager (integrated controller) policies that control the entire wireless network from a global point of view. Reliability, bandwidth, robustness and power considerations are taken into account for policy decisions.A simulation framework to experiment with different hardware configurations and network topologies and constraints. The developed framework will be help to validate and update our theories. This tool that will be made available through the web will be invaluable for other researchers in designing future energy-efficient wireless multimedia systems.