Brian M. Blum

Range-free localization schemes for large scale sensor networks

Wireless Sensor Networks have been proposed for a multitude of location-dependent applications. For such systems, the cost and limitations of the hardware on sensing nodes prevent the use of range-based localization schemes that depend on absolute point-to-point distance estimates. Because coarse accuracy is sufficient for most sensor network applications, solutions in range-free localization are being pursued as a cost-effective alternative to more expensive range-based approaches. In this paper, we present APIT, a novel localization algorithm that is range-free. We show that our APIT scheme performs best when an irregular radio pattern and random node placement are considered, and low communication overhead is desired. We compare our work via extensive simulation, with three state-of-the-art range-free localization schemes to identify the preferable system configurations of each. In addition, we study the effect of location error on routing and tracking performance. We show that routing performance and tracking accuracy are not significantly affected by localization error when the error is less than 0.4 times the communication radio radius.

RAP: a real-time communication architecture for large-scale wireless sensor networks

Large-scale wireless sensor networks represent a new generation of real-time embedded systems with significantly different communication constraints from traditional networked systems. This paper presents RAP, a new real-time communication architecture for large-scale sensor networks. RAP provides convenient, high-level query and event services for distributed micro-sensing applications. Novel location-addressed communication models are supported by a scalable and light-weight network stack. We present and evaluate a new packet scheduling policy called velocity monotonic scheduling that inherently accounts for both time and distance constraints. We show that this policy is particularly suitable for communication scheduling in sensor networks in which a large number of wireless devices are seamlessly integrated into a physical space to perform real-time monitoring and control. Detailed simulations of representative sensor network environments demonstrate that RAP significantly reduces the end-to-end deadline miss ratio in the sensor network.

EnviroTrack: towards an environmental computing paradigm for distributed sensor networks

Distributed sensor networks are quickly gaining recognition as viable embedded computing platforms. Current techniques for programming sensor networks are cumbersome, inflexible, and low-level. We introduce EnviroTrack, an object-based distributed middleware system that raises the level of programming abstraction by providing a convenient and powerful interface to the application developer geared towards tracking the physical environment. EnviroTrack is novel in its seamless integration of objects that live in physical time and space into the computational environment of the application. Performance results demonstrate the ability of the middleware to track realistic targets.

AIDA: Adaptive application-independent data aggregation in wireless sensor networks

Sensor networks, a novel paradigm in distributed wireless communication technology, have been proposed for various applications including military surveillance and environmental monitoring. These systems deploy heterogeneous collections of sensors capable of observing and reporting on various dynamic properties of their surroundings in a time sensitive manner. Such systems suffer bandwidth, energy, and throughput constraints that limit the quantity of information transferred from end-to-end. These factors coupled with unpredictable traffic patterns and dynamic network topologies make the task of designing optimal protocols for such networks difficult. Mechanisms to perform data-centric aggregation utilizing application-specific knowledge provide a means to augmenting throughput, but have limitations due to their lack of adaptation and reliance on application-specific decisions. We, therefore, propose a novel aggregation scheme that adaptively performs application-independent data aggregation in a time sensitive manner. Our work isolates aggregation decisions into a module that resides between the network and the data-link layer and does not require any modifications to the currently existing MAC and network layer protocols. We take advantage of queuing delay and the broadcast nature of wireless communication to concatenate network units into an aggregate using a novel adaptive feedback scheme to schedule the delivery of this aggregate to the MAC layer for transmission. In our evaluation we show that end-to-end transmission delay is reduced by as much as 80% under heavy traffic loads. Additionally, we show as much as a 50% reduction in transmission energy consumption with an overall reduction in header overhead. Theoretical analysis, simulation, and a test-bed implementation on Berkeleys MICA motes are provided to validate our claims.

Range-free localization and its impact on large scale sensor networks

With the proliferation of location dependent applications in sensor networks, location awareness becomes an essential capability of sensor nodes. Because coarse accuracy is sufficient for most sensor network applications, solutions in range-free localization are being pursued as a cost-effective alternative to more expensive range-based approaches. In this paper, we present APIT, a novel localization algorithm that is range-free. We show that our APIT scheme performs best when an irregular radio pattern and random node placement are considered, and low communication overhead is desired. We compare our work, via extensive simulation, with three state-of-the-art range-free localization schemes to identify the preferable system configurations of each. In addition, we provide insight into the impact of localization accuracy on various location dependent applications and suggestions on improving their performance in the presence of such inaccuracy.

An entity maintenance and connection service for sensor networks

In this paper, we present a middleware architecture for coordination services in sensor networks that facilitates interaction between groups of sensors which monitor different environmental events. It sits on top of the native routing infrastructure and exports the abstraction of mobile communication endpoints maintained at the locations of such events. A single logical destination is created and maintained for every environmental event of interest. Such destinations are uniquely labeled and can be used for communication by application-level algorithms for coordination and sensory data management between the different event locales. For example, they may facilitate coordination, in a distributed intrusion scenario, among nodes in the vicinity of the intruders.We evaluate our middleware architecture using GloMoSim, a wireless network simulator. Our results illustrate the success of our architecture in maintaining event-related communication endpoints. We provide an analysis of how architectural and network dependent parameters affect our performance. Additionally we provide a proof of concept implementation on a real sensor network testbed (Berkeleys MICA Motes).

A communication architecture and programming abstractions for real-time embedded sensor networks

Data distribution in embedded real-time sensor networks requires new protocols and programming environments that achieve time-sensitive message delivery and provide useful abstractions to the application programmer Attainment of these goals requires changes to multiple layers of the communication protocol stack. In this paper, we review a protocol suite developed by the authors for data communication in embedded sensor networks. It takes into account time constraints and exports attribute-based connections that are tightly integrated with properties of the monitored environment. A programming language is described that allows external physical objects to be represented as first class abstractions in the computing System. The language facilitates writing monitoring applications. The system was implemented on a prototypical sensor network based on MICA motes.