Manportable unit pushes mobile networking limits.
A prototype personal communications and situational awareness system may provide U.S. warfighters with an advantage in tactical combat. The device will link soldiers to a mobile voice and data network with the capability to share important information among individuals and entire units. A built-in inertial geolocation subsystem will enable troops to determine their location even if global positioning system signals are jammed or unavailable.
As warfare moves away from large, vulnerable formations to small, agile units, accurate command and control becomes a priority. With more responsibility and autonomy given to individual warfighters, personal communications systems and a situational awareness capability will be necessary to coordinate fluid operations.
The Defense Advanced Research Projects Agency (DARPA) is developing a technology testbed to demonstrate the feasibility of a small unit situational awareness system. According to Dr. Paul J. Kolodzy, program manager at DARPA’s Advanced Technology Office in Arlington, Virginia, the situational awareness program originated in a 1996 study by the Defense Science Board. The report concluded that units will be widely scattered across future battlefields, requiring unprecedented amounts of situational awareness data to enhance their combat capabilities.
Based on the study’s results, in 1997 DARPA began the situational awareness system (SAS) program as part of its broader small unit operations (SUO) program. The SUO SAS program seeks to develop a device that will serve as a soldier’s personal communication and location system. It must function under a variety of conditions while receiving and disseminating information from multiple sources such as sensors and other soldiers. Software will process the data and automatically transmit it across the battlefield, allowing soldiers to concentrate on the battle rather than on remembering location and transmission information, Kolodzy says.
The program’s first goal is to develop extreme radio frequency (RF) agility, which is the ability to shift bands quickly to suit the environment in which the soldier is working. This feat is achieved through software designed to provide the optimum amount of bandwidth to match communication needs. Extreme RF agility allows the SUO SAS radio to switch to specific bands automatically under circumstances such as high frequency transmissions in urban environments and low frequency transmissions in heavily forested regions.
Transmission power will become more important to widely dispersed battery-power-dependent units, and power will be saved by opting for low power broadcasts, Kolodzy says. The SUO SAS radios will relay messages through each other, forming nodes within a mobile network. This approach significantly reduces individual units’ power requirements and decreases the chances of detection by enemy forces, he explains.
Research is underway to create the software necessary to form, maintain and administer the highly adaptive, peer-to-peer, self-forming mobile communications networks envisioned by the program. Kolodzy concedes that it is a major challenge to build networking technology directly into the radio that now only resides in fixed infrastructure or vehicle-mounted units.
DARPA is also developing an ad hoc information management system to maintain the network and create a database accessible to warfighters. The database can be used hierarchically—unit commanders requesting information can then send it to their superiors or disseminate it among their troops. For example, a soldier sees a formation of enemy tanks and inputs the descriptive data into his SUO SAS device where it becomes part of the mobile network’s database. If another soldier enters the area and requests a situational update, the software in the first soldier’s radio will pass on the data about the tanks. Kolodzy declares that is really what SUO is all about: how to take all this information as well as how to take cell towers and tower-type fixed infrastructure and move them into a radio.
To meet these performance requirements, the technology for the small unit situational awareness device is pushing the current state of the art, Kolodzy maintains. Depending on operational circumstances, the device will be able to transmit from 10 bits per second up to 4 megabits per second. Frequency agility will allow soldiers to communicate in ranges from 20 megahertz to 2.5 gigahertz, enabling the radio to provide and acquire geolocation data. The system will also include an enhanced anti-jamming capability, he says.
The radio will feature a beyond-line-of-sight lifeline mode. Soldiers separated from their units by tens of miles will be able to maintain connectivity by sending short messages from a very long range. According to Kolodzy, this function trades off data rate for distance because the transmissions are only 10 to 100 bits per second—just enough to provide a status report.
The SUO SAS technology is intended to allow the creation of an autonomous adaptive network that is scalable up to 10,000 nodes. The nodes do not have to be individual soldiers; they can represent voice communications or data from unattended ground sensors and unmanned aerial vehicles, Kolodzy points out. A tiered, hierarchical architecture will be used to manage these multinode networks. The advantage of this system is that it allows scalability, he observes. The first tier will comprise up to 50 nodes; a second tier connects the nodes in the first tier within a hierarchy; and a third tier extends the network’s range to other communications systems.
A continuing challenge in the program is writing the software to correlate all of the data the SUO SAS system will process. Kolodzy notes that DARPA only now is beginning to take its first steps into this data fusion domain. The immediate goal is to demonstrate the technical feasibility of conducting low-level data correlation. To accomplish this task, the data rate must be reduced and the required pieces of information combined into one superset. “We will demonstrate that we can pass data to the correct place and the correct unit, depending upon its location and position in the hierarchy,” he says.
One cutting-edge technology used by the program is multicasting, the ability to disseminate voice and data systematically across variable bandwidths. Successfully providing these types of transmissions will require a deeper insight into how information is broadcast, Kolodzy claims. He adds that these experiments provide DARPA with some of its first insights into multicasting capabilities and challenges.
Voice communication is still important in the SUO SAS peer-to-peer network. However, message latency becomes a critical issue because any major delay in a transmission as it travels from node to node will render the message unintelligible. DARPA wants to reduce latency below 200 milliseconds from the time a soldier begins speaking to the time the message is received, but achieving this without a fixed infrastructure has proven to be challenging, he says.
Maintaining a mobile network poses another difficulty because it consists of individual soldiers leaving and entering local subnets. A related issue is how to maintain a list of who is on a given subnet and what hierarchy they belong to. “What information should be provided and what information should be received from them?” Kolodzy asks. He wants the program to demonstrate some of the mobile networking capabilities during the next year and highlight areas where new technologies need to be developed.
The SUO SAS radio has a software definable architecture that allows it to be integrated into systems such as Land Warrior and the Warfighter Information Network-Terrestrial programs. The radio also can be programmed to accept existing frequencies such as the single channel ground-to-air system and the enhanced position location reporting system or the future joint tactical radio system waveform. A satellite communications capability is also possible, but Kolodzy notes that it is not part of the program at this time.
Each radio acts as a repeater to save power and to facilitate peer-to-peer networking. For example, if a soldier wishes to send a message to another unit member who is 100 yards away, and several warfighters are located between them, the intervening soldiers’ radios will relay the message. This capability can be achieved even if the device is not worn. Kolodzy suggests one possibility is to drop simpler versions of the radio around a battlefield to act as relays and links to the outside world if troops are in an area where it is hard to communicate.
A warfighter’s geographic location and relation to other soldiers are represented through a graphical format that will appear on a portable computer screen or helmet-mounted view piece. A cable port in the radio allows situational awareness data to interface with equipment such as Land Warrior battle gear. However, Kolodzy notes that the Land Warrior program must first determine whether the SUO program’s presentation style meshes with its system.
The radio’s situational awareness system incorporates a geopositioning subsystem that allows it to determine location by communicating with other radios. The device also possesses a built-in global positioning system (GPS). However, if GPS signals are jammed or unavailable, the unit can determine its position in three dimensions through an inertial navigation system and a barometer to gauge altitude.
During the technology demonstration phase in 2002, a geopositioning subunit will be attached to the bottom of the prototype unit’s backpack. This device will comprise a GPS unit, an inertial system and a barometer that will all interface into the SUO SAS system. However, the final system may not have all of these sensors, Kolodzy warns. While the prototype will be large and bulky to demonstrate all the possible technologies, field testing will determine what trade-offs are necessary to provide the maximum amount of data in the smallest, lightest package.
The prototype technology demonstrator will be a backpack-sized unit. Because the goal is to show how the device functions, larger field programmable gate arrays (FPGAs) will be used to load and test new algorithms in the field instead of application specific integrated circuits (ASICs). The system will be considerably smaller once the FPGAs are replaced with ASICs, Kolodzy says. After the technology is proven in field tests, the smaller version may be available for trials by late 2003.
When fully miniaturized, the radio will fit in a container roughly 8 inches long by 3.5 inches wide that can be attached to a backpack or worn on a belt. The device will contain processors, RF subsystems and an IBM microdisc drive to store data. The current prototype is in the final design stage. It will be built in the first half of 2002 with field tests scheduled in late summer and early fall.
The SUO SAS program seeks to provide a technology that can be quickly transitioned to the services in four to five years, Kolodzy explains. This time frame will require additional hardware substantiation before the radio is ready for testing. If the prototype is complete in 2002, it will probably be one or two years before another version incorporating new advances is made. It is during this second phase that the services will determine where the SAS fits into their programs, he says.
Additional information on DARPA’s small unit operations situational awareness system is available on the World Wide Web at http://www.darpa.mil/ato/programs/suosas.htm.