Because of their inherently autonomous nature, wireless sensor networks allow the warfighter—from a standoff position—to maintain situational awareness and persistent monitoring of all aspects of an urban environment, made possible by the capability to “set and forget” thousands of low-cost, lowpower sensors across rooftops, in alleyways, and inside buildings. The goal of the NEST program is to coordinate the operation of these distributed embedded sensor networks by developing the necessary underlying information services. The NEST team has already undertaken to improve many of these services, pursuing such developments as algorithms for self-localization in a Global Positioning Systemdeprived environment, efficient ad hoc routing, security, multitiered fault tolerance, and time synchronization. Most recently, the NEST team has begun to apply distributed sensors to support warfighter operational needs. The team created the largest wireless sensor network established to date—a 1,000-node, robust autonomous ad hoc sensor network, dispersed over an area approximately 1 × .25 km in an operationally relevant environment—to demonstrate monitoring and protection of long, linear areas. In another effort, NEST engineers developed algorithms to locate small-arms fire in highreverberation environments as an adjunct to the multipath locative method. Finally, to provide battlespace awareness to the participants of the Team Patriot 2005 exercise, the NEST team successfully integrated multiple, geographically dispersed sensor fields within a single small unmanned air vehicle. The use of distributed sensors to support warfighter operational needs is the common thread connecting these NEST accomplishments; however, even the best information is useless without an overarching information management system to allow its global accessibility. The JBI provides this access by aggregating, integrating, fusing, and intelligently disseminating relevant battlespace knowledge to those who need it most.

The JBI was born from the SAB vision to establish a flexible interoperability layer between information systems, as opposed to the traditional architecture comprising stovepiped legacy systems. The key to this envisioned interoperability is the use of the Common Applications Programming Interface, which presents client applications with a consistent interface to the services supplied by the JBI. A vital service offered by the JBI is the ability to connect information producers to information consumers via publish-and-subscribe mechanisms. These mechanisms allow the JBI to push new information, as soon as it arrives from publishers, to all subscribers registered to receive that information. Therefore, the information displayed by JBI-enabled remote network monitoring applications is always current, and the JBI user has a means to remotely monitor these networks to ensure their operability.

An essential JBI feature is its capacity to manage network information as distinct information object types. When a client application registers with the JBI as either a publisher or a subscriber, that client must specify the information object type it will be exchanging. This specification enables producers and consumers interested in the same information to be connected through the JBI. The JBI can also manage data from different wireless sensor network applications as distinct information types. Again, when registering with the JBI, network monitoring applications must subscribe to specific information types, allowing the remote monitor to receive updates only from those network applications it has interest in monitoring. This useful feature enables different monitors for the various sensor networks.

Another JBI service, the ability to archive published information and provide it to applications for later query, is important to NEST users. Remote network monitoring applications employ this “information persistence” to provide replay functionality and allow users to review network activity over a period of time.

Due to the challenges involved with large-scale deployment, AFRL engineers have not yet tested the NEST/JBI architecture against a field the size of the ExScal demonstration. However, the team plans to increase the number of sensors to stress-test the architecture. The engineers will then present the architecture at upcoming NEST meetings involving members of US Special Operations Command (USSOCOM), DARPA, and the Defense Intelligence Agency. Concurrent to completing these activities, the team will continue to develop and enhance NEST services in anticipation of the technology’s upcoming transition to USSOCOM in Fiscal Year 2007.

Mr. Mark Oliver and Mr. Ryan Sites, of the Air Force Research Laboratory’s Information Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn_index.asp. Reference document IF-H-06-05.

¹ Scientific Advisory Board. “Building the Joint Battlespace Infosphere.” Technical Report SAB-TR-99-02, US Air Force, Dec 00.
² JBI Program Office. “Reference Implementation Quick-Start Guide.” Core Services Reference Implementation Version 1.2.5, AFRL, Jul 05.
³ Arora, A., Bapat, S., and Kulathumani, V. “Analyzing the Yield of ExScal, a Large- Scale Wireless Sensor Network Experiment.” 13th IEEE International Conference on Network Protocols, vol 53, no 62 (Nov 05): 6-9.