Technology trends are extending the flexibility and convenience of today's sensor networks through the introduction of new capabilities such as multi-frequency radio transceivers, GPS, and innovative system management tools. This paper expands upon these motivations to present an integrated general-purpose MultimodAl system for NeTworks of In-situ wireless Sensors (MANTIS). The MANTIS system promotes multimodal flexibility and ease of use through its support for multimodal sensing including GPS-enabled location and time, multi-frequency communication, multitasking sensor nodes, and a new multi-platform operating system called MANTIS OS (MOS). For the novice, MANTIS provides convenient tools such as a simple cross-platform API, a remote shell for debugging and logging into MOS nodes, fine-grained dynamic reprogramming via the radio, and in-board sensor placement. For the expert, MANTIS supports true networked emulation of MOS sensor nodes as X86 processes, as well as seamless bridging between an X86-based network of MOS virtual sensors and an actual sensor network of active physical MOS nodes, called nymphs.

Geolocation of Internet hosts enables a diverse and interesting new class of location-aware applications. Previous measurement-based approaches use reference hosts, called landmarks, with a well-known geographic location to provide the location estimation of a target host. This leads to a discrete space of answers, limiting the number of possible location estimates to the number of adopted landmarks. In contrast, we propose Constraint-Based Geolocation (CBG), which infers the geographic location of Internet hosts using multilateration with distance constraints, thus establishing a continuous space of answers instead of a discrete one. CBG accurately transforms delay measurements to geographic distance constraints, and then uses multilateration to infer the geolocation of the target host. Our experimental results show that CBG outperforms the previous measurement-based geolocation techniques. Moreover, in contrast to previous approaches, our method is able to assign a confidence region to each given location estimate. This allows a location-aware application to assess whether the location estimate is sufficiently accurate for its needs.

This paper proposes TSync, a novel lightweight bidirectional time synchronization service for wireless sensor networks. TSync's bidirectional service offers both a push mechanism for accurate and low overhead global time synchronization as well as a pull mechanism for on-demand synchronization by individual sensor nodes. Multi-channel enhancements improve TSync's performance. We deploy a GPS-enabled framework in live sensor networks to evaluate the accuracy and overhead of TSync in comparison with other in-situ time synchronization algorithms

We present Topology-based Geolocation (TBG), a novel approach to estimating the geographic location of arbitrary Internet hosts. We motivate our work by showing that 1) existing approaches, based on end-to-end delay measurements from a set of landmarks, fail to outperform much simpler techniques, and 2) the error of these approaches is strongly determined by the distance to the nearest landmark, even when triangulation is used to combine estimates from different landmarks. Our approach improves on these earlier techniques by leveraging network topology, along with measurements of network delay, to constrain host position. We convert topology and delay data into a set of constraints, then solve for router and host locations simultaneously. This approach improves the consistency of location estimates, reducing the error substantially for structured networks in our experiments on Abilene and Sprint. For networks with insufficient structural constraints, our techniques integrate external hints that are validated using measurements before being trusted. Together, these techniques lower the median estimation error for our university-based dataset to 67 km vs. 228 km for the best previous approach.

Abstract—The attenuation, depolarization, and fluctuation of a microwave signal going through a tree canopy are investigated by developing a Monte Carlo based coherent scattering model. In particular, the model is used to analyze the performance of global positioning system (GPS) receivers under tree canopies. Also the frequency and time-domain channel characteristics of a forest are investigated when a transmitter is outside and a receiver is inside a forest. A fractal algorithm (Lindenmayer system) is used to generate the structure of coniferous or deciduous trees whose basic building blocks are arbitrarily oriented finite cylinders, thin dielectric needles, and thin dielectric disks. Attenuation and phase change of the mean field through foliage is accounted for using Foldy’s approximation. Scattering of the mean field from individual tree components and their images in the underlying ground plane are computed analytically and added coherently. Since tree trunks and some branches are large compared to the wavelength and may be in the close proximity of the receiver, a closed-form and uniform expression for the scattered near-field from dielectric cylinders is also developed. Monte Carlo simulation of field calculation is applied to a cluster of trees in order to estimate the statistics of the channel parameters, such as the probability density function (pdf) of the polarization state of the transmitted field, path loss, and the incoherent scattered power (the second moment of the scattered field), as a function of the observation point above the ground. Index Terms—Channel simulation, propagation, vegetation. I.

Recently, geographic routing in wireless networks has gained attention due to several advantages of location information. Location information eliminates the necessity to set up and maintain explicit routes, which reduces communication overhead and routing table size. These advantages allow scalability especially in dynamic and unstable wireless networks. However, no matter which technologies or techniques a location system uses, its measurements will have some amount of quantifiable inaccuracy depending on environment and system. These inaccuracies may affect the performance and even correctness of geographic routing. However, thus far, these impacts have not been studied in-depth. In this paper, we analyze the impact of location inaccuracy on geographic routing. First, we model location inaccuracy metrics- absolute location inaccuracy, relative distance inaccuracy, absolute location inconsistency and relative distance inconsistency. Then, we analyze how location inaccuracy metrics affect the building blocks of geographic routing including greedy forwarding and local maximum resolution. We use extensive NS-2 simulations to evaluate the performance of geographic routing using a wide array of parameter settings including inaccuracy level, node degree and network diameter. In our simulation results, reasonable location inaccuracy (of 20 percent or less of radio range) caused packet drop reaching up to 54 percent, non-optimal path up to 53 percent and packet looping. These observations indicate the importance of re-visiting geographic routing protocols, and the significance of considering location inaccuracy in their design and evaluation. I.

Abstract: The mobile commerce sector and in particular the context sensitive advertising will represent a high yield revenue stream. This paper introduces the Ad-me (Advertising for the Mobile E-commerce user) system. The Ad-me is a mobile tourist guide that proactively delivers advertisements to users based upon perceived individual user needs together with their location. A Multi-Agent Systems (MAS) design philosophy is adopted. In order to achieve maximum content diffusion a range of presentation formats are accommodated including HTML, WML, HDML and iMode. 1.

Most routing protocols in MANET adopt the popular Random Waypoint model for its simplicity and suitability for theoretical study and analysis. Recently, several entity, group and scenario based mobility models and frameworks have been proposed to model much more realistic and practical movements of mobile nodes in real scenarios. Although some work exists in evaluating routing protocols based on such specific scenarios, and some effort in adapting a protocol to suit mobility has been made, there does not exist any protocol that makes direct use of mobility information to route packets within a MANET. In this work, we first develop a practical mobility model that recognizes an orbital pattern in the sociological movement of mobile users, and then propose a novel Orbit Based Routing (OBR) protocol, that leverages the underlying orbital mobility to accurately determine a set of likely regions containing any node in the MANET. By forming a distributed location database among acquaintances and employing a scalable geographic routing to forward packets among nodes, OBR emerges as a clear choice for MANET routing in the face of practical mobility. We propose three different schemes of OBR and compare their performance against an

A major hurdle in evaluating routing protocols for a

Recently, geographic routing in wireless networks has gained attention due to several advantages of location information. Location information eliminates the necessity to set up and maintain explicit routes. These advantages allow scalability especially in dynamic and unstable wireless networks. However, no matter which technologies or techniques a location system uses, its measurements will have some amount of quantifiable inaccuracy depending on environment and system. These inaccuracies may a#ect the performance and even correctness of geographic routing. However, thus far, these impacts have not been studied in-depth. In this paper, we analyze the impact of location inaccuracy on geographic routing. Our study shows the significant impact of location inaccuracy on the performance of geographic routing in terms of packet drops, non-optimal paths and routing loops.