Connectionless Networks Enhance Sensor Efficiency
Program seeks to develop smart, flexible remote monitoring equipment, data architectures.
The goal of the Defense Advanced Research Projects Agency’s (DARPA’s) connectionless networks program is to change the way remote devices such as this prototype sensor manage power and data transmissions.
A new network management technology soon may change the ways unattended ground sensors are designed and operated. By focusing on the radio systems that link individual devices, scientists hope to create an intelligent networking architecture that uses the radio’s full communications capability both to conserve energy in a passive mode and to provide brief high-bandwidth data streams. Such operational flexibility would allow the development of multisensor devices able to activate a variety of onboard applications from microphones to real-time streaming video to meet intelligence collection needs.
The goal of the Defense Advanced Research Projects Agency’s (DARPA’s) connectionless networks (CN) initiative is to change the way remote sensor systems manage power and data transmissions, explains Preston F. Marshall, the CN program manager in the agency’s Advanced Technology Office, Arlington, Virginia. He notes that with the availability of more sensitive and capable sensors, it is becoming more attractive to remove warfighters from some high-risk battlefield positions and replace them with networked robotic sensors.
But while smaller and more efficient sensors are available, the communications systems linking small, unattended devices have remained relatively unchanged.
DARPA’s goal is to build very low-energy systems that can hold a network together but that also can meet sudden spikes in use.
Persistent sensing presents several unique challenges. In the past, he notes, designers coupled their sensors with radios developed for other missions. “If we’re really going to be effective at creating persistent sensing over regions, we’re going to have to rethink the technology,” he says.
The goal of the CN program is to develop systems that can adapt to a variety of changing mission needs. CN also seeks to save power by reducing demand on the network and the individual sensors in it.
DARPA scientists have developed devices that can power up and shut off in sub-millisecond time frames, which will allow sensors to conserve energy until they detect something. When a target is identified, the sensors will activate the appropriate applications to monitor the activity and then shut down as soon as possible.
Another aspect that makes sensor networking unique is the assumption in traditional networking that events occur randomly. But sensor networks are correlated—if something happened in one part of the network it is probably taking place somewhere else. “If an event occurs at this millisecond, it’s probably occurring at the next millisecond. Unique among the networking community, we have the advantage of seeing the future because the future probably looks a lot like the very recent past,”
Program researchers are working to further develop this predictive capability by having the network configure itself ahead of predicted demand. For example, the latency for the first new information packet in a connectionless sensor network may be two seconds, but all the following data packets relating to a specific event will transmit within milliseconds. The network finds the most efficient path to transmit the information, briefly becoming a high-speed network before returning to a power conservation mode.
At the heart of the research is the challenge of making every node on the network and its neighbors adapt individually. For example, in a sensor field, a cluster of devices in one area may detect movement. Instead of activating the entire network, only that small group of devices will increase their data transmissions, perhaps switching from passive audio to active video surveillance.
Software programming for connectionless networks also shares some similarities to DARPA research with disruption-tolerant networking. “In IP [Internet protocol] networks, the network is a dumb thing. It either delivers packets or throws them away. In a connectionless network, the network takes responsibility,”
|DARPA’s research will allow unattended sensors such as this video surveillance system to more effectively form and maintain networks. The program also seeks to create a new generation of multipurpose sensors capable of switching from passive audio to active video monitoring as the situation requires.|
By transmitting data locally as opposed to end-to-end, connectionless networks can save large amounts of power. Internet protocol (IP) was designed for large file transfers, but sensor networks usually transmit only in small bursts of a few bits of information.
Connectionless networking is about four orders of magnitude away from true efficiency. He notes that, compared to wireless protocols such as 802.11 operating mobile ad hoc networks, the DARPA technology requires at least two or three orders of magnitude less energy to operate than current commercial wireless systems.
Phase one of the CN program worked out basic technical concepts. Phase two was a laboratory implementation that set the technology’s parameters by determining when the network would rest and when it would report data.
The goals for phase three are making the networks both self-managing and self-optimizing. At the end of this 15-month phase, the nodes will be able to automatically adapt themselves and change their settings to meet network requirements,
One challenge for the CN program is integrating how designers look at analog and network protocols. DARPA is working with the U.S. Army Research Laboratory (ARL), which is conducting its own investigation of sensor and low-energy radio technology.
Writing software that will allow sensors to manage power is a major challenge for the program’s next phase.
The network itself is another important environment. For example, if the network’s sensors detect a large amount of vehicular traffic, it will try to optimize its data paths to provide the right amount of data for the mission. The difference between a connectionless network and other types of architectures is that the system identifies heavy use along certain data paths and attempts to optimize the efficiency of those transmissions. The network may in fact decide to use more energy to collect more data about a target. “It’s kind of like a little venture capitalist in each node thinking about investment strategies—what’s the best place to use energy and how fast will it pay back,” he shares.
Another program goal is for the network to be able to surge up to 1 megabit per second to provide real-time video and audio. This feature will allow engineers to develop multipurpose sensor systems and devices.
DARPA Connectionless Networks: www.darpa.mil/ato/programs/CN/index.htm