Jonathan W. Hui

The dynamic behavior of a data dissemination protocol for network programming at scale

To support network programming, we present Deluge, a reliable data dissemination protocol for propagating large data objects from one or more source nodes to many other nodes over a multihop, wireless sensor network. Deluge builds from prior work in density-aware, epidemic maintenance protocols. Using both a real-world deployment and simulation, we show that Deluge can reliably disseminate data to all nodes and characterize its overall performance. On Mica2-dot nodes, Deluge can push nearly 90 bytes/second, one-ninth the maximum transmission rate of the radio supported under TinyOS. Control messages are limited to 18% of all transmissions. At scale, the protocol exposes interesting propagation dynamics only hinted at by previous dissemination work. A simple model is also derived which describes the limits of data propagation in wireless networks. Finally, we argue that the rates obtained for dissemination are inherently lower than that for single path propagation. It appears very hard to significantly improve upon the rate obtained by Deluge and we identify establishing a tight lower bound as an open problem.

IP is dead, long live IP for wireless sensor networks

A decade ago as wireless sensor network research took off many researchers in the field denounced the use of IP as inadequate and in contradiction to the needs of wireless sensor networking. Since then the field has matured, standard links have emerged, and IP has evolved. In this paper, we present the design of a complete IPv6-based network architecture for wireless sensor networks. We validate the architecture with a production-quality implementation that incorporates many techniques pioneered in the sensor network community, including duty-cycled link protocols, header compression, hop-by-hop forwarding, and efficient routing with effective link estimation. In addition to providing interoperability with existing IP devices, this implementation was able to achieve an average duty-cycle of 0.65%, average per-hop latency of 62ms, and a data reception rate of 99.98% over a period of 4 weeks in a real-world home-monitoring application where each node generates one application packet per minute. Our results outperform existing systems that do not adhere to any particular standard or architecture. In light of this demonstration of full IPv6 capability, we review the central arguments that led the field away from IP. We believe that the presence of an architecture, specifically an IPv6-based one, provides a strong foundation for wireless sensor networks going forward.

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

Securing the deluge Network programming system

A number of multi-hop, wireless, network programming systems have emerged for sensor network retasking but none of these systems support a cryptographically-strong, public-key-based system for source authentication and integrity verification. The traditional technique for authenticating a program binary, namely a digital signature of the program hash, is poorly suited to resource-contrained sensor nodes. Our solution to the secure programming problem leverages authenticated streams, is consistent with the limited resources of a typical sensor node, and can be used to secure existing network programming systems. Under our scheme, a program binary consists of several code and data segments that are mapped to a series of messages for transmission over the network. An advertisement, consisting of the program name, version number, and a hash of the very first message, is digitally signed and transmitted first. The advertisement authenticates the first message, which in turn contains a hash of the second message. Similarly, the second message contains a hash of the third message, and so on, binding each message to the one logically preceding it in the series through the hash chain. We augmented the Deluge network programming system with our protocol and evaluated the resulting system performance

Extending IP to Low-Power, Wireless Personal Area Networks

Extending IP to low-power, wireless personal area networks (LoWPANs) was once considered impractical because these networks are highly constrained and must operate unattended for multiyear lifetimes on modest batteries. Many vendors embraced proprietary protocols, assuming that IP was too resource-intensive to be scaled down to operate on the microcontrollers and low-power wireless links used in LoWPAN settings. However, 6LoWPAN radically alters the calculation by introducing an adaptation layer that enables efficient IPv6 communication over IEEE 802.15.4 LoWPAN links.

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

Connecting low-power and lossy networks to the internet

Many applications, ranging from wireless healthcare to energy metering on the smart grid, have emerged from a decade of research in wireless sensor networks. However, the lack of an IP-based network architecture precluded sensor networks from interoperating with the Internet, limiting their real-world impact. Given this disconnect, the IETF chartered the 6LoWPAN and RoLL working groups to specify standards at various layers of the protocol stack with the goal of connecting low-power and lossy networks to the Internet. We present the standards proposed by these working groups, and describe how the research community actively participates in this process by influencing their design and providing open source implementations.

IPv6 in Low-Power Wireless Networks

With deeply embedded wireless sensors, a new tier of the Internet is emerging that will extend into the physical world. These wireless sensor nodes are expected to vastly outnumber conventional computer hosts as we see them today, but their strict resource constraints are unlike other technologies already common to the Internet. As wireless sensor network research took off, many in the field eschewed the use of IP as inadequate and in contradiction to the needs of wireless sensor networking. Since then, the field has matured and IP has evolved. In this paper, we show that the convergence of Internet Protocol Version 6 (IPv6) and low-power multihop wireless networking is possible, pragmatic, and efficient-especially in regard to the metrics that matter most for embedded applications, low memory footprint, high reliability, and low energy usage. Using real commercial deployments, we show that it is possible to simultaneously achieve an average duty cycle of <; 0.4%, average message delivery rate of > 99.9%, and average per-hop latency of <; 125 ms over 12 months in different environments.

Low power mesh networking with Telos and IEEE 802.15.4

A family of low power wireless sensor network devices have been built to enable research and deployments. The devices have featured commercial off the shelf (COTS) components integrated together on a platform commonly referred to as a ”mote”, designed by the University of California, Berkeley. Motes have been used to evaluate wireless sensor network algorithms as well as for environmental monitoring and object tracking deployments. Miniature wireless devices are ideal for high density long term deployments in areas otherwise unsuitable for wired connections or passive devices. We designed and built a new mote platform, Telos (see Figure 1), for use in ultra low power wireless sensor networks [3]. Featuring a TI MSP430 microcontroller, a CC2420 IEEE 802.15.4 compliant radio, and built in sensors, Telos is the lowest power mote to date. IEEE 802.15.4 provides packet handling support and sophisticated channel encoding and encryption not found in previous wireless transceivers. Using these new primitives, we show robust, low power wireless mesh networking using IEEE 802.15.4.