Loren P. Clare

An integrated architecture for cooperative sensing networks

Distributed sensor networks (DSNs) consisting of many small, low-cost, spatially dispersed, communicating nodes have been proposed for many applications, such as area surveillance and environmental monitoring. Trends in integrated electronics, such as better performance-to-cost ratios, low-power radios, and microelectromechanical systems (MEMS) sensors, now allow the construction of sensor nodes with signal processing, wireless communications, power sources and synchronization, all packaged into inexpensive miniature devices. If these devices can be easily deployed and self-integrated into a system, they promise great benefits in providing real-time information about environmental conditions. Intelligent sensor nodes function much like individual ants that, when formed into a network, cooperatively accomplish complex tasks and provide capabilities greater than the sum of the individual parts. The paper discusses several technical challenges that must be overcome to fully realize the viability of the DSN concept in realistic application scenarios.

Self-organizing distributed sensor networks

Advances in CMOS IC and micro electrical-mechanical systems (MEMS) technologies are enabling construction of low-cost building blocks each of which incorporates sensing, signal processing, and wireless communications. Collections of these integrated microsensor nodes may be formed into sensor networks in a wide variety of ways, with characteristics that depend on the specific application--the total number of nodes, the spatial density, the geometric configuration (e.g., linear vs. areal), topographic aspects (e.g., smooth vs. rough terrain), and proximity and proportion of user/sink points. The power of these distributed sensor networks will be unleashed by means of their ability to self-organize, i.e., to bootstrap and dynamically maintain organizational structure befitting the purpose and situation that is presented, without the need for human assistance. A prototype sensor system and networking protocols are being developed under the DARPA/TTO AWAIRS Program and are described.

Load balanced, energy-aware communications for Mars sensor networks

The deployment and operation of self-organizing sensor networks is envisioned to play a key role in space exploration, such as for future in situ exploration of Mars. Sensors are equipped with several measurement instruments and are able to cooperate autonomously and to collect scientific measurements (seismic, chemicals, temperature, etc.). One or more landers or rovers functioning as base stations periodically (or on demand) collect measurements and relay the aggregated sensor field results to an orbiter and from the orbiter back to Earth. In this paper, we propose an efficient routing scheme for Mars sensor networks exploiting the similarity of operations between the wireless, multi-hop communications network connecting instruments (sensors) and rover(s) and the packet radio network used in a typical ad hoc networking environment. A critical issue in routing strategy design that sets the Mars sensor network apart from conventional ad hoc networks is energy conservation and prolonging network lifetime while maintaining connectivity and satisfying latency constraints. Simulation results show that with energy aware path selection, a more even distribution of energy consumption among nodes is developed and leads to longer network life time.

Development platform for self-organizing wireless sensor networks

Distributed microsensor networks, built from collections of nodes each having the ability to sensor their environment, process the raw sensor data in cooperation with other neighboring nodes into information and then communicate that information to end users. These systems are designed to be self-organizing in the sense of establishing and maintaining their own network without the need for specialistic operators. In most envisioned applications, wireless communications are the most practical means of interconnection, eliminating the internode cabling. Long periods of autonomous operations in remote environments will need battery or other renewable energy sources. In order to prolong battery life, all node hardware and software functions need to be designed to consume minimal power. In general, a node will expend energy on local processing of sensor data to produce compressed information in order to reduce communications. These network systems are intended to support large numbers of such nodes to cover large geographic areas.

Wireless integrated network sensors: toward low-cost and robust self-organizing security networks

A very important benefit of continuing advances in CMOS IC technology is the ability to construct a wide variety of micro electrical mechanical systems (MEMS), including sensors and RF components. These building blocks enable the fabrication of complete systems in a low-cost module, which include sensing, signal processing, and wireless communications. Together with innovative and focused network design techniques that will make possible simple deployment and sustained low- power operation, the small size and cost can be enabling for a very large number of law enforcement and security applications, including remote reconnaissance and security zones ranging from persons to borders. We outline how the application can be exploited in the network design to enable sustained low-power operation. In particular, extensive information processing at nodes, hierarchical decision-making, and energy conserving routing and network topology management methods will be employed in the networks under development.

Autoconfigurable distributed control systems

This paper discusses ongoing research on automatically configurable distributed control systems. We are investigating the use of networks of relatively small controllers that contain intelligence and communication capabilities to perform factory automation. These systems are expected to be more robust, adaptable and flexible than conventional designs. To achieve these benefits, fundamental changes in the underlying control system architecture are needed. The system architecture is divided into two portions: the control infrastructure and the control algorithms. Requirements for the control infrastructure are described that implement basic services to support distributed control, including the ability for a new control node to announce its presence and capabilities to the system without disrupting ongoing activities. The control algorithms for this system must be designed with certain properties: autonomy and cooperativeness; that are able to respond to changes in the physical plant and its usage. A laboratory for studying autoconjigurable control systems is under development using prototype distributed controllers on a CAN-based network. Two experiments are described that demonstrate autoconfiguration capability. The potential applications and the future directions of this research are discussed.

A Taxonomy of Distributed Real-time Control Systems

Abstract The demands placed on industrial automation systems have grown in many dimensions over the last two decades. Examples of such demands are increased size, functionality, speed, flexibility, simpler programming, quality, and decreased installation and commissioning costs. An emerging approach to meeting such demands is the use of Distributed Real-time Control System (DRCS) architectures and technologies. This chapter discusses key issues that are driving this trend in modern industrial automation systems and provides a framework for discussion and technological research.

Endpoint naming for space delay / Disruption Tolerant Networking

Delay/Disruption Tolerant Networking (DTN) provides solutions to space communication challenges such as disconnections when orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other operational constraints.12 DTN is critical to enabling the future space internetworking envisioned by NASA. Interoperability with international partners is essential and standardization is progressing through both the CCSDS and the IETF.

Considerations on communications network protocols in deep space

Deep space missions impose numerous unique constraints that impact the communications architectural choices. We are entering the era where networks that exist in deep space are needed to support planetary exploration. Identification is made of the various distinctive elements that drive the selection of the communications protocol suite. Cost-effective performance will require a balanced integration of applicable widely used standard protocols with new and innovative designs.

The Deep Impact Network Experiment Operations Center

Delay/Disruption Tolerant Networking (DTN) promises solutions in solving space communications challenges arising from disconnections as orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other phenomena. DTN has been identified as the basis for the future NASA space communications network backbone, and international standardization is progressing through both the Consultative Committee for Space Data Systems (CCSDS) and the Internet Engineering Task Force (IETF). JPL has developed an implementation of the DTN architecture, called the Interplanetary Overlay Network (ION). ION is specifically implemented for space use, including design for use in a real-time operating system environment and high processing efficiency. In order to raise the Technology Readiness Level of ION, the first deep space flight demonstration of DTN was performed using the Deep Impact (DI) spacecraft. Called the Deep Impact Network (DINET), operations occurred during Autumn 2008. An essential component of the DINET project was the Experiment Operations Center (EOC), which generated and received experiment communications traffic as well as “out-of-DTN band” command and control traffic, archived DTN flight test information in a database, provided display systems for monitoring DTN operations status and statistics (e.g., bundle throughput), and supported query and analyses of the data collected. This paper describes the DINET EOC and its value in the DTN flight experiment and potential for further DTN testing. The DINET EOC housed ground nodes that produced and consumed “payload” data that was relayed through the DTN router on board the DI spacecraft. The EOC also controlled the topology among the nodes, altering the connectivity to test DTN functionality. An additional node in the EOC acted to perform administrative functions, and contained the Monitor and Control System to view experiment health and concurrently collect and analyze the data delivery status and statistics. The software diagnostic messages and protocol diagnostic messages issued by network nodes were collected analyzed and stored into a database in real-time. The DINET EOC was located within the JPL Protocol Technology Lab (PTL). The PTL provides connectivity to other NASA centers and external entities, and is itself a node in the larger DTN Experiment Network (DEN). The DINET EOC is envisioned to become a general tool in this broader context of experimental testing of DTN across a geographically dispersed user community.