Sukun Kim

Health monitoring of civil infrastructures using wireless sensor networks

A Wireless Sensor Network (WSN) for Structural Health Monitoring (SHM) is designed, implemented, deployed and tested on the 4200 ft long main span and the south tower of the Golden Gate Bridge (GGB). Ambient structural vibrations are reliably measured at a low cost and without interfering with the operation of the bridge. Requirements that SHM imposes on WSN are identified and new solutions to meet these requirements are proposed and implemented. In the GGB deployment, 64 nodes are distributed over the main span and the tower, collecting ambient vibrations synchronously at 1 kHz rate, with less than 10 mus jitter, and with an accuracy of 30 muG. The sampled data is collected reliably over a 46-hop network, with a bandwidth of 441 B/s at the 46th hop. The collected data agrees with theoretical models and previous studies of the bridge. The deployment is the largest WSN for SHM.

Trio: enabling sustainable and scalable outdoor wireless sensor network deployments

We present the philosophy, design, and initial evaluation of the Trio testbed, a new outdoor sensor network deployment that consists of 557 solar-powered motes, seven gateway nodes, and a root server. The testbed covers an area of approximately 50,000 square meters and was in continuous operation during the last four months of 2005. This new testbed in one of the largest solar-powered outdoor sensor networks ever constructed and it offers a unique platform on which both systems and application software can be tested safely at scale. The testbed is based on Trio, a new mote platform that provides sustainable operation, enables efficient in situ interaction, and supports fail-safe programming. The motivation behind this testbed was to evaluate robust multi-target tracking algorithms at scale. However, using the testbed has stressed the system software, networking protocols, and management tools in ways that have exposed subtle but serious weaknesses that were never discovered using indoor testbeds or smaller deployments. We have been iteratively improving our support software, with the eventual aim of creating a stable hardware-software platform for sustainable, scalable, and flexible testbed deployments

Flush: a reliable bulk transport protocol for multihop wireless networks

We present Flush, a reliable, high goodput bulk data transport protocol for wireless sensor networks. Flush provides end-to-end reliability, reduces transfer time, and adapts to time-varying network conditions. It achieves these properties using end-to-end acknowledgments, implicit snooping of control information, and a rate-control algorithm that operates at each hop along a flow. Using several real network topologies, we show that Flush closely tracks or exceeds the maximum goodput achievable by a hand-tuned but fixed rate for each hop over a wide range of path lengths and varying network conditions. Flush is scalable; its effective bandwidth over a 48-hop wireless network is approximately one-third of the rate achievable over one hop. The design of Flush is simplified by assuming that different flows do not interfere with each other, a reasonable restriction for many sensornet applications that collect bulk data in a coordinated fashion, like structural health monitoring, volcanic activity monitoring, or protocol evaluation. We collected all of the performance data presented in this paper using Flush itself.

Reliable transfer on wireless sensor networks

Many applications in wireless sensor networks, including structure monitoring, require collecting all data without loss from the nodes. End-to-end retransmission, which is used in the Internet for reliable transport, becomes very inefficient in wireless sensor networks, since wireless communication, and constrained resources pose new challenges. We look at factors affecting reliability, and search for efficient combinations of the possible options. Information redundancy like retransmission, and erasure codes, can be used. Route fix, which tries alternative next hop after some failures, also reduces packet loss. We implemented and evaluated these options on a real test bed of Berkeley Mica2Dot motes. Our experimental results show that each option overcomes different kinds of failures. Link-level retransmission is efficient but limited in achieving reliability. Erasure code enables very high reliability by tolerating packet losses. Route fix responds to link failures quickly. Previous work had found it difficult to increase reliability past a certain threshold. We show that the right combination of primitives can yield more than 99% reliability with low overhead, providing a viable alternative to end-to-end retransmission over multiple hops.

Marionette: using RPC for interactive development and debugging of wireless embedded networks

A main challenge with developing applications for wireless embedded systems is the lack of visibility and control during execution of an application. In this paper, we present a tool suite called Marionette that provides the ability to call functions and to read or write variables on pre-compiled, embedded programs at run-time, without requiring the programmer to add any special code to the application. This rich interface facilitates interactive development and debugging at minimal cost to the node

Wireless sensor networks for structural health monitoring

Sukun Kim†, Shamim Pakzad‡, David Culler†, James Demmel† Gregory Fenves‡, Steve Glaser‡, Martin Turon? {binetude, culler, demmel}@eecs.berkeley.edu {shamimp, fenves, glaser}@ce.berkeley.edu mturon@xbow.com † Electrical Engineering and Computer Sciences and ‡ Civil and Environmental Engineering ? Crossbow Technology, Inc. University of California at Berkeley 4145 N. First Street Berkeley, CA 94720 San Jose, CA 95134

A modular sensornet architecture: past, present, and future directions

ion that supports existing implementations, more so than building a narrow waist that exports a set of services that new implementations are expected to adhere to. While future applications may use such features, the disregard for these interfaces by current protocols, coupled with the desire to maintain a lean narrow waist, leads to a top-down focus. In designing the unifying link layer abstraction for T2 [20], our approach has been quite different. We began with a foundation similar to the previous version, pruning unneeded services and functionality. More importantly we synthesized a list of requirements for a diverse set of protocols and applications in order to ensure support in the upcoming version. We also focused on integrating cross-layer services, such as security and power management, working closely with developers of these stand-alone components and focused architectures. The result is a new link abstraction which we feel is lean, yet provides the essential set of services needed to support the majority of higher-level services.

High-fidelity environmental monitoring using wireless sensor networks

The system is environment monitoring service based on Wireless Sensor Networks (WSN). Users can know temperature, humidity, light, and CO2 level in real time. Excessive electricity consumption by lighting in the office can be saved and the quality of the office environment can become better by controlling lighting and CO2 level.