9:30, SPEC-L2.1
BLUETOOTH - AD-HOC NETWORKING IN AN UNCOORDINATED ENVIRONMENT
J. HAARTSEN
Recently, a new universal radio interface called Bluetooth TM was developed enabling electronic devices to connect and communicate via short-range radio links. The technology allows the design of low-power, small-sized, and low-cost radios that can be embedded in a wide range of future products. The Bluetooth system operates in the unlicensed Industrial-Scientific-Medical (ISM) band at 2.4 GHz which is globally available. Bluetooth radios use frequency hopping to spread their signals and to provide resistance against interference from other Bluetooth hoppers and other radio transmitters in the band. This paper addresses the challenges to provide ad-hoc network functions in the Bluetooth system. Both the needs for frequency hopping and the lack of a central controller in ad-hoc radio networks have placed special requirements on the design of the air interface. The paper further describes the co-existence of and bridging between independently hopping piconets, the concept of scatternets, and discusses hop synchronization in general.

9:50, SPEC-L2.2
INSTRUMENTING THE WORLD WITH WIRELESS SENSOR NETWORKS
D. ESTRIN, L. GIROD, G. POTTIE, M. SRIVASTAVA
Pervasive micro-sensing and actuation may revolutionize the way in which we understand and manage complex physical systems:from airplane wings to complex ecosystems. The capabilities for detailed physical monitoring and manipulation offer enormous opportunities for almost every scientific discipline, and it will alter the feasible granularity of engineering. We identify opportunities and challenges for distributed signal processing in networks of these sensing elements and investigate some of the architectural challenges posed by systems that are massively distributed, physically-coupled, wirelessly networked, and energy limited.

10:10, SPEC-L2.3
LOCATIONING IN DISTRIBUTED AD-HOC WIRELESS SENSOR NETWORKS
C. SAVARESE, J. RABAEY, J. BEUTEL
Evolving networks of ad-hoc, wireless sensing nodes rely heavily on the ability to establish position information. The algorithms presented herein rely on range measurements between pairs of nodes and the a prioricoordinates of sparsely located anchor nodes. Clusters of nodes surrounding anchor nodes cooperatively establish confident position estimates through assumptions, checks, and iterative refinements. Once established, these positions are propagated to more distant nodes, allowing the entire network to create an accurate map of itself. Major obstacles include overcoming inaccuracies in range measurements as great as ±50%, as well as the development of initial guesses for node locations in clusters with few or no anchor nodes. Solutions to these problems are presented and discussed, using position error as the primary metric. Algorithms are compared according to position error, scalability, and communication and computational requirements. Early simulations yield average position errors of 5% in the presence of both range and initial position inaccuracies.

10:30, SPEC-L2.4
ENERGY EFFICIENT PROTOCOLS FOR LOW DUTY CYCLE WIRELESS MICROSENSOR NETWORKS
S. CHO, A. CHANDRAKASAN
Emerging distributed wireless microsensor networks will enable the reliable and fault tolerant monitoring of the environment. Such microsensors are required to operate for years from a small energy source, while maintaining reliable communication link to the basestation. The design of energy-aware communication protocols can have a dramatic impact on the network lifetime for such applications. A detailed communication energy model, obtained from measurements, is introduced that incorporates the non-ideal behavior of the physical layer electronics. This includes the start-up energy cost of the RF tranceiver, which dominates energy dissipation for short packet sizes. Using this model, various communication layer protocols are explored for asymmetrical sensor networks such as machine monitoring. The paper also proposes the use of a variable bandwidth allocation scheme, that exploits spatial distribution of sensors.

10:50, SPEC-L2.5
DYNAMIC PHYSICAL LAYERS FOR WIRELESS NETWORKS USING SOFTWARE RADIO
V. BOSE, R. HU, R. MORRIS
The communication parameters in mobile ad-hoc net-works, such as the distance between nodes, channel characteristics, and user demands can vary quickly. Using traditional design techniques and creating a static physical layer designed to meet worst case conditions will result in poor performance and resource utilization under most operating conditions. Software radios, which implement their physical layer processing in software, provide a solution to this problem by enabling the physical layer to be modified to best meet the current conditions. This paper describes the initial work on a software radio-based ad-hoc network that allows the physical layer to be modified on a per packet basis.

11:10, SPEC-L2.6
SECURE SCALABLE VIDEO STREAMING FOR WIRELESS NETWORKS
S. WEE, J. APOSTOLOPOULOS
We present a wireless video streaming system that securely and efficiently streams video to heterogeneous clients over time-varying communication links. Clients may differ in their display, power, communication, and computational capabilities and wire-less channels may have time-varying bandwidths and quality levels that depend on channel usage and channel conditions. End-to-end system efficiency is achieved by placing transcoders at intermediate network nodes; these transcoders can easily adapt the video stream for particular client capabilities and network conditions. This system uses our proposed method of secure scalable streaming (SSS) to simultaneously achieve scalability, efficiency, and security. Specifically, an SSS coder encodes video into secure scalable packets by using jointly designed scalable video coding, packetization, and progressive encryption techniques. This allows downstream SSS transcoders to transcode the secure scalable packets by simply truncating or eliminating packets, and without decrypting the coded video. A key feature of SSS is that it enables low-complexity transcoding operations to be performed at inter-mediate network nodes without compromising the security of the end-to-end wireless streaming system.