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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. We propose a new dual-radio network architecture to improve communication reliability in wireless sensor networks. Specifically, we show that radio transceivers operating at well-separated frequencies and spatially separated antennas offer robust communication, high link diversity, and better interference mitigation. We derive the optimal parameters for the dual-transceiver setup from frequency and space diversity in theory. We observe that frequency diversity holds the most benefits as long as the antennas are sufficiently separated to prevent coupling. Our experiments on an indoor/outdoor testbed confirm the theoretical predictions and show that radio diversity can significantly improve end-to-end delivery rates and network stability at only a small increase in energy cost over a single radio. Simulation experiments further validate the improvements in multiple topology configurations, but also reveal that the benefits of radio diversity are coupled to the number of available routing paths to the destination.

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., TNGNES

Body sensor networks are a key component in the emerging trend towards personalised healthcare monitoring and the mobile health paradigm. These networks consist of miniaturized devices, mounted on the human body that continuously monitor and communicate the subject's vital signs to a basestation device for real time viewing, sharing, and remote diagnosis by health professionals. Security is a stringent requirement as these devices communicate personal medical data, and mishandling can result in serious ethical implications and massive liabilities. Traditional security mechanisms, however, are not suited to the resource constraints of these small devices, or the fundamental limitations of their operating environment. Adapting and devising new solutions to satisfactorily encrypt and authenticate the communication of these devices is an open research area. In this thesis, we present three mechanisms to address specific and realistic security concerns of body sensor networks:First, we propose a secret-key generation mechanism that uses reciprocal and unique properties of the wireless channel between two communicating devices to generate secret-key bits to encrypt communications. Existing schemes of this type frequently yield mismatching key bits, thereby requiring reconciliation schemes with high implementation and energy costs. In our work, we identify and address the root cause of bit mismatch, and restrict bit generation to dynamic periods when bit agreement is high. As a result, we eliminate the need for reconciliation itself. Our mechanism is extremely lightweight and generates perfectly matching secret key bits at a rate suited to the typical needs of bodyworn devices.Second, we suggest an enhancement to secure broadcast communication for bodyworn devices. The literature proposes the use of time-varying secret keys to encrypt group communications. However, packet loss is very common for bodyworn devices, and key updates may not be received by all parties, renderin

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.