Acoustical Ranging Techniques in Embedded Wireless Sensor Networked Devices

Location sensing provides endless opportunities for a wide range of applications in GPS-obstructed environments; where, typically, there is a need for higher degree of accuracy. In this article, we focus on robust range estimation, an important prerequisite for fine-grained localization. Motivated by the promise of acoustic in delivering high ranging accuracy, we present the design, implementation and evaluation of acoustic (both ultrasound and audible) ranging systems.We distill the limitations of acoustic ranging; and present efficient signal designs and detection algorithms to overcome the challenges of coverage, range, accuracy/resolution, tolerance to Doppler’s effect, and audible intensity. We evaluate our proposed techniques experimentally on TWEET, a low-power platform purpose-built for acoustic ranging applications. Our experiments demonstrate an operational range of 20 m (outdoor) and an average accuracy 2 cm in the ultrasound domain. Finally, we present the design of an audible-range acoustic tracking service that encompasses the benefits of a near-inaudible acoustic broadband chirp and approximately two times increase in Doppler tolerance to achieve better performance

Secret Key Generation Rate vs. Reconciliation Cost Using Wireless Channel Characteristics in Body Area Networks

Abstract—In this paper, we investigate the feasibility of real-time derivation of cryptographic keys in body area networks using unique characteristics of the underlying wireless channel. We perform experiments to confirm that motion does indeed provide significant highly correlated randomness on either end of the wireless link between basestation and mobile mote to enable real-time key generation. Furthermore, we demonstrate that channel characteristics for a dynamic body area network consist of two different components, a fast and a slow component, each of which make a qualitatively different contribution to key generation. These components can be isolated to address specific needs of the application scenario: the fast component can yield high entropy keys at a fast rate between basestation and mobile mote with some bit disagreement between the two devices; the slow component generates keys at a lower rate but with very high level of bit agreement. Our experimental results highlight this tradeoff, and our key generation protocol details the key extraction process. I

Some Three-Dimensional Graph Drawing Algorithms

In order to realise the potential benefits of three--dimensional (3D) display of relational information, there is a need for effective 3D human--computer interface designs. Algorithms for automatically creating 3D visual representations of relational information are a significant component of these interfaces. One productive strategy for developing such algorithms has been via the graph as an intermediate representation of the relational information: the information is first expressed as a graph and then a layout algorithm is used to create a visual representation of the graph. This thesis examines some technical issues which arise when several common layout algorithms, developed originally for 2D display of graphs, are extended specifically to 3D display. Typical computer graphics display systems can only provide a limited resolution and display area. This places a limit on the size of graph which can be displayed effectively. Simplification of the graph can permit the display of lar..

Packet pacing in short buffer optical packet switched networks

Abstract — In the absence of a cost-effective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. This paper investigates the resulting impact on end-to-end loss and throughput, and proposes that the optical edge switches “pace ” packets into the OPS core to improve performance without adversely affecting end-to-end delays. In this context, our contributions are three-fold. We first evaluate the impact of short buffers on the performance of real-time and TCP traffic. This helps us identify short-time-scale burstiness as the major contributor to performance degradation, so we propose that the optical edge switches pace the transmission of packets into the OPS core while respecting their delay-constraints. Our second contribution develops algorithms of poly-logarithmic complexity that can perform optimal real-time pacing of high data rate traffic. Lastly, we show via simulations of a realistic network carrying real-time traffic that pacing can significantly reduce losses at the expense of a bounded increase in end-to-end delay. The loss-delay trade-off mechanism provided by pacing can help achieve desired OPS network performance. I

Radio diversity for reliable communication in sensor networks

Radio connectivity in wireless sensor networks is highly intermittent due to unpredictable and time-varying noise and interference patterns in the environment. Because link qualities are not predictable prior to deployment, current deterministic solutions to unreliable links, such as increasing network density or transmission power, require overprovisioning of network resources and do not always improve reliability

Radio diversity for reliable communication in WSNs

Deployment of wireless sensors in real world environments is often a frustrating experience. The quality of radio links is highly coupled to unpredictable physical environments, leading to intermittent connectivity and frequent outages. Because link qualities are not predictable prior to deployment, current deterministic solutions to unreliable links, such as increasing network density or transmission power, do not adequately address this issue. We propose a new dual radio network architecture to improve communication reliability in wireless sensor networks. Specifically, we show that radio transceivers operating at dual widely spaced radio frequencies and through spatially separated antennas offer robust communication, high link diversity, and better interference mitigation. We show through experiments that radio diversity can significantly improve end-to-end delivery rates, network stability, and transmission costs at only a slight increase in energy cost over a single radio