Research Team Seeks Solutions for Warfighters on the Move
Government-commercial effort creates new capabilities for the U.S. Army’s major programs.
Warfighters on patrol in Iraq often operate with limited bandwidth in difficult radio frequency situations such as when there is jamming, reduced bandwidth and bad weather conditions. The goal of the U.S. Army’s Communications and Networks Collaborative Technology Alliance (C&N CTA) is to create applications for tactical wireless communications systems. The alliance is developing applications that will become part of larger communications programs directly benefiting soldiers in the field.
The U.S. Army is conducting basic research to develop niche tactical wireless solutions that can be moved quickly into larger programs. The effort is a partnership among government, commercial and academic organizations that permits them to pool their resources and share the benefits of new developments.
Many different technologies are required to make a complete communications system. The goal of the Communications and Networks Collaborative Technology Alliance (C&N CTA) is to create applications for mobile tactical operations. According to Gregory Cirincione, cooperative agreement manager at the Army Research Laboratory (ARL),
Mobile wireless networks possess attributes unique to the Army’s ground environment, Cirincione says. A key service requirement is the ability to conduct operations on the move within a highly mobile network infrastructure. The unusual aspect of this architecture is not that the nodes are moving but that the entire infrastructure is moving as well. “This is not a cell tower kind of thing where you have a fixed infrastructure and mobile nodes. This is where all the cell towers are moving,” he says.
Because bandwidth and energy requirements are a vital consideration for warfighters that are on the move, the C&N CTA supports research on low-power sensor, soldier and mobile networks designed to optimize limited bandwidth. “Most of our resources are targeted toward that very mobile environment where you have very limited resources and also where you do not always have strategic resources,” Cirincione says.
Researchers are mitigating the resource gap using domain services such as autoconfiguration. A major issue for the Army’s Future Combat Systems (FCS) and its other advanced technology programs is that mobile networks must be deployed rapidly in an ad hoc manner yet remain coherent. “How do you take a network and deploy it someplace in 96 hours and get it up and running by itself without a bunch of network engineers?” he asks.
The alliance’s autoconfiguration solution created a set of protocols that allows a network to configure itself automatically. Researchers discovered recently that the technology has a scalability problem in large networks—as more systems are added, the network begins to slow down. One solution is to divide the network into domains. The Internet features multiple hierarchical domains that allow it to scale, and this concept can be applied to wireless systems. “Our problem is that everything moves. So one of the things we’ve been working on very heavily for the last two or three years has been what we call domain autoconfiguration,” Cirincione shares.
Domain autoconfiguration consists of techniques that configure and reconfigure networks into domains while on the move. This work focuses on developing protocols to operate the system and techniques to maintain domain optimization. He notes that these efforts have been successful with many protocols entering programs at the Army’s Communications–Electronics Research Development and Engineering Center (CERDEC),
Another C&N CTA program explores applications for reliable and secure server pooling, which maintains network services on a mobile battlefield. This research seeks to prevent end-to-end communications disruptions. Researchers have developed software protocols that provide secure services to mobile battlefield nodes. As links are disrupted because of movement, the protocols seamlessly connect users to needed resources.
Key management for battlefield cryptographic applications also is a development priority. In public key cryptography systems, when users are issued their keys, they must go to a certificate authority to validate their identification. In the federal government, the authority is usually a separate agency such as the National Security Agency. But Cirincione maintains that warfighters do not have this luxury. The C&N CTA is examining ways to provide soldiers with passwords and public key information that do not require access to strategic services in the continental
Researchers also are modifying the physical and media access control (MAC) layers of tactical communications equipment. Cirincione explains that the alliance is developing multi-input, multi-output systems, which involves installing multiple antennas on a receiver and transmitter. Using many antennas increases throughput and interference rejection and jam resistance because the equipment uses the diversity of a channel’s spectrum. He notes that this approach is very successful and that tests with an experimental system have achieved high throughput communications.
But technical challenges remain. One hurdle is reducing antenna complexity to cut manufacturing costs. In addition, C&N CTA members are working on enhancing signal processing capabilities because high-bandwidth communications systems must operate in electromagnetically noisy environments.
Because the ARL and the C&N CTA are focused on tactical operations, enhancement to systems such as unattended ground sensors are under their mandate. Cirincione notes that sensor networks have an advantage of being innately less mobile so they do not have the connectivity issues associated with more mobile applications. But power consumption remains a concern for these systems. “In most of our protocol research, energy is a key factor. Even for the systems that aren’t sensor networks, energy is going to be a major issue,” he says.
The C&N CTA also is working on waveforms and signal processing such as multicarrier waveforms using orthogonal frequency modulation (OFM) that efficiently access noncontiguous spectrum. OFM waveforms can exploit noncontiguous spectrum in a variety of ways, including mitigating issues such as the channel fade that occurs when a unit moves. “If you come into an area and there is noise because there are other people using spectrum, what you want to do is to use noncontiguous chunks of spectrum. One of the issues that the military has is a lack of spectrum,” Cirincione says.
Research has focused on Internet protocol version 6 (IPv6) applications to address management issues. Cirincione explains that one of the disadvantages of tactical mobile wireless systems is that they are modeled on the Internet’s architecture. The Internet has two architectural drawbacks that do not make it a good medium for mobile wireless communications. First, the Internet network transport layers are isolated from each other, which allows for scalability in landline systems. “It was inefficient, but the pipes were very big, so it didn’t matter,” he explains.
|One challenge of modern mobile warfare is that both the users and the entire network infrastructure must move together. The C&N CTA|
is developing technologies to manage and configure networks automatically without the need for technicians to be present.
However, addresses do not work this way in tactical wireless systems. The C&N CTA conducted many address management projects to identify addresses and to decouple them from their physical location. Another advantage of IPv6 is that it offers users more flexibility in the number of addresses they can use, but Cirincione says that protocols are still required to locate and maintain those addresses as they move.
Because the alliance develops technologies that must operate in cluttered terrestrial environments, its researchers continue to face recurring challenges. The issues include resource constraints due to limited bandwidth, energy for power and processing, and processing capabilities. “I can come up with waveforms that have great signal processing, but they won’t operate on the processors that are in the radios. So you’re always looking for low-complexity solutions,” he says.
Network dynamics for complex systems also pose difficulties. The Army’s plans call for highly dynamic mobile networks that can adapt to a variety of mission requirements and that feature mobile nodes and network infrastructure, which Cirincione says are often overlooked by planners. However, all routers, domain name services, mobility services and security authorities are now mobile. “How do you have everything mobile and still provide services to the soldier?” he asks.
Another issue is what Cirincione refers to as the “channel problem.” This is an environment where high levels of jamming, intermittent connectivity and congestion in wireless channels are all present. Interference of all kinds adversely affects existing wireless protocols that were designed originally for landline networks. An example of this challenge is the Internet transmission control protocol (TCP). When connectivity begins to fail, the TCP assumes that the network is congested. To lessen resource pressure, the protocol decreases its footprint on the network by lengthening the intervals between messages. This strategy does not work well in a wireless environment because the most likely failure mechanism is not congestion but an error because of channel noise. “If you back off, you make it worse. In reality, you have to change your protocols for that noisy channel,” he says.
Wireless systems also rely heavily on centralized services. Many of the protocols in use require centralized servers that cannot support widely dispersed units relying on radio communications. Another challenge is scalability because networks are difficult to model when they become very large. He adds that the C&N CTA is working on methods to better assess the impact of larger networks.
Technologies based on the alliance’s research are beginning to find their way into Army intrusion detection systems for network security. Cirincione explains that these applications use MANET protocols operating within a larger cooperative protocol managing a network routing infrastructure. MANET protocols are used in multihop radio communications. He notes that for point-to-point communications, a protocol is required to determine where the recipient is to receive the multihop transmission packets. But this control traffic is vulnerable to jamming, spoofing and infiltration.
To counter this potential threat, the C&N CTA is specifying rules for intrusion detection schemes for multihop environments. In Internet-based intrusion detection systems, traffic can be controlled through a gateway. But this type of application cannot work with MANET-based wireless systems because all of the nodes are communicating with many other nodes that are not channeling through a single gateway.
Cirincione explains that based on its experience, the research community has learned several lessons. One is the need to create domains to manage scalability; another is cross-layer design for wireless systems. To have high performance and energy efficiency, the protocol layers must be linked and designed jointly. For example, routing must be linked to the MAC layer to optimize the protocol. “If you don’t know what that media access is and if you don’t know if you have a high band or a low band—you don’t know what the channel looks like—you’re going to be suboptimal. We can’t afford that,” he says.
The C&N CTA will continue its work for another three years before its mandate expires. Cirincione notes that there is a great degree of stakeholder involvement in terms of the ARL and technical advisory boards that review the program. CERDEC and a research management board also review and modify the program.
One of the many advantages of the program is its flexibility and ability to adjust to the technology. This is a key element for the program concept. “You can’t create this program and expect it to just run along this road map for five years. Technology is going to change; everything is going to change. So you want to be able to adapt and to adapt to breakthroughs that you make,” he says.
The Communications and Networks Collaborative Technology Alliance (C&N CTA) is a cooperative research organization consisting of government and commercial research organizations. It includes federally funded facilities such as the U.S. Army Research Laboratory (ARL),
According to Gregory Cirincione, ARL cooperative agreement manager, the arrangement is unique because it is not a lead, prime or subcontractor type relationship. It is a consortium of members that jointly and collaboratively develop research plans and conduct research.
The lead organization of the C&N CTA is Telcordia Technologies,
Once a technology is developed, the alliance accelerates its transition to programs of note. A research management board helps facilitate this process. The board includes members from a variety of Army commands such as CERDEC and other services. Its members help the C&N CTA define the niches that new technologies can fill.
Cirincione notes that as a basic research organization, it is difficult for the C&N CTA to move a technology directly to warfighters because of the many intermediate steps required. One tool to help speed these transactions is a transition contract. This document executes task order contracts with consortium members to accelerate the transition of promising technologies. He says that all of the contract details are prearranged, making the document a more flexible vehicle to transition technologies faster.
Another feature of the C&N CTA is that its partner organizations create long-lasting alliances. This allows members to exploit specific technologies in a program. For example, some alliance partners have won programs from the Defense Advanced Research Projects Agency, the Warfighter Information Network–Tactical or the Future Combat Systems by transitioning new technologies.
The organization’s research development engineering centers, which work directly with program managers and contractors, direct the technology transition. Cirincione notes that this process is important to the alliance because of its focus on niche technologies. By solving niche problems in a larger program, it is much easier to pull those developments directly into the program, he says.