The Future: Bringing Down Barriers to Wireless Communications

By Anne Cady, Richard Games, Ed Palo, Jason Providakes, and Glenn Roberts

People told this issue's cover boy, Alexander Graham Bell, that it was impossible to send the human voice over a wire. Today, wireless mobile devices have revolutionized the way we get information and communicate. Could Bell have imagined this when he helped start the communications revolution?

ITRE is working on a number of transformation programs for sponsors, including research designed to improve communications 10 or more years ahead. To look at what the future holds, The Edge editors sat down with MITRE's chief engineers to discuss critical communications problems facing our customers and the possible solutions to be found in emerging technologies.

Much of the commercial world has already moved from fixed, wired networks to point-to-point wireless communication via a fixed infrastructure. For many of our government sponsors, however, the communications transformation means moving out of fixed infrastructure into ad hoc wireless networks—being mobile and flexible.

This move is key to the Department of Defense vision of net-centric warfare—in which everyone can exchange information in near-real time—and to a lot of other government agencies, such as the Department of Homeland Security. The elements of robust wireless communications—including mobility, adaptability, reliability, security, and management—are written into the future plans of the Federal Aviation Administration as well. Whether the goal is improving air traffic control, equipping the modern warfighter with better communications tools, gathering intelligence, or protecting the nation's borders, government agencies want advances that will expand and improve networks, stretch the bounds of wireless connectivity, and ensure the security of information passing through the communications infrastructure.

The ubiquity of wireless devices is evident on the streets of almost any town in America, where everyone seems to be on his or her cellphone or PDA. Connectivity is getting better all the time, and most people expect reliable service and instant access. But move to a less structured environment and the problems of wireless communications are obvious. Whether in the middle of Baghdad or in the aftermath of Hurricane Katrina, the limits of wireless and mobile communications can lead to deadly situations.

Today's wireless capabilities are limited by many factors, from available technology to the physical environment—such as the ones our troops face in Iraq and Afghanistan. These environments create huge challenges, explains Jason Providakes, chief engineer for the Washington Command, Control & Communications Center. First there's the heat and sand; then there are signal barriers, such as the buildings of downtown Baghdad and the dense caves of Afghanistan, which block signals or bounce them around.

For military ground forces, the challenge can be summed up in the phrase, "the last tactical mile." It's critical that the front-line soldier on the move remain connected to the network—including others at the tactical edge, as well as to air and ground support—while operating in these challenging environments.

MITRE is pursuing many ways to improve wireless communications for our sponsors, both in our work programs and in our research.

A key concept of net-centricity throughout the Department of Defense is interoperability. To be able to share information across units, services, and with allies, all communications systems must be able to "talk" to each other—for example, by using the same standard software protocols.

Spectrum.

As wireless communications proliferate, a critical dilemma facing users all over the world—civilian, government, military, and commercial aviation—is the finite capacity of the radio frequency (RF) spectrum on which wireless depends. (See the article on page 3 for more on spectrum.) For example, the future of aviation air-to-ground communication is driven by spectrum availability and the need for greater productivity, says Glenn Roberts, chief engineer for the Center for Advanced Aviation System Development. While we can buy time by slicing the spectrum into thinner wedges, he says, the key to the future is to move to new technologies and find ways to automate and share spectrum.

One emerging technology we are studying—which will help with spectrum limitations—is free space optical communication. Free space optical communication transmits data from primary fiber-optic lines through the air to a user by means of lasers. Although it offers high bandwidth relatively inexpensively, its links are susceptible to degradation from atmospheric conditions such as fog, and they require direct lines of sight. Therefore, the challenge is to provide optimal communications bandwidth without giving up all-weather RF reliability. To overcome these limitations, MITRE is researching ways to improve free space optical technology. It is vital for airborne networks and for helping small autonomous networks link together via satellite or ground infrastructures—thus bridging the gap caused by the inability to scale mobile networks.

"It's an immense challenge," says Ed Palo, chief engineer in the Center for Air Force Command & Control Systems. A start has been made with the Joint Tactical Information Distribution System (JTIDS/Link 16), which creates digital links across a number of platforms, says Palo, but it lacks an Internet-like protocol, which would increase its flexibility, connectivity, and applicability to evolving net-centric applications.

Antennas.

Another technology area that needs improvement to support wireless, mobile communications is antennas. Getting the right antenna for the environment is a major hurdle—especially at a reasonable price. Particularly in ground mobile tactical applications, the typical one-piece omni-directional antenna has limitations, such as data collisions, jamming, and signal fading. Adaptive antennas, however, can mitigate multipath signal fading, as well as filter out background noise and other interference, intentional or unintentional.

MITRE is working with adaptive array antennas—a circle or grid of numerous antennas whose outputs can be combined to point in desired directions in phases, and even to become "smart" enough—given the right kind of digital signal processing system—to keep adjusting the antenna to the right direction by knowing only the signal.

What makes the problem particularly vexing for on-the-move networks—airborne or on the ground—is that they call for two antennas that can point to each other on the fly and constantly adjust. In the airborne environment, the problems are compounded by the limitations in the number, size, and location of available antenna apertures. Experiments are under way at MITRE to address these problems.

Another challenge MITRE is working on for the future is building an airborne network, which the Air Force and the civil aviation community could use with all flight platforms to communicate air-to- ground and air-to-air using satellite links. For example, all warplanes in a theater would be able to exchange information in near-real-time through the airborne network. The critical challenge here is the speed at which these network nodes move around in relation to each other and to mobile and stationary units on the ground.

Interoperability.

A key concept in the DOD, one which supports net-centric warfare, is interoperability. To be able to share information across units and services, and with allies, systems must be able to "talk" to each other. Interoperability is also critical to many other government organizations; for example, in matters of homeland security, military and intelligence units share information with Customs and Border Patrol and often with state agencies.

On the battlefield, when netcentric warfare is the norm, each soldier will have a mobile wireless communication device—for example a software radio, satellite phone, or PDA. Their devices will automatically detect who else is near and how to connect. The resulting networks won't need any physical configuration in advance—unlike, for example, most current military networks, which are pre-configured, with information flowing through routers and switches at pre-determined places. The new networks automatically connect when wireless-equipped soldiers come into range of each other, enabling timely communication, accessibility of networked services and data, and uninterrupted connectivity.

MITRE and many other research organizations are exploring ways to accomplish such on-the-fly, interoperable networks, looking at various techniques called mesh networks, ad hoc networks, or self-forming networks.

An ad hoc network is a collection of communication devices (or nodes) created to communicate with no fixed infrastructure available or pre-determined organization of available links. These networks, which can be built around any wireless technology, are common in the military but are also appropriate for other uses that require temporary networks. Small ad hoc networks have been created and tested in the field but there's still a lot of work to be done in the areas of theory, research, and prototypes, says Palo. One significant issue is scale, and the protocols available so far don't scale well to create the large networks the military needs.

Another future technology we are researching is "self-healing" (or self-forming) networks. These are networks that can learn how to route information when one part of the network is disabled or unavailable. A self-healing network has the advantage of keeping people connected at critical times, without the need to drag extensive support personnel to the front line to fix problems.

MITRE is researching a number of technologies to improve communications for warfighters in the field, such as self-healing (or self-forming) networks. These networks will find ways to route information around a disabled section of the network, making sure warfighters are connected at all times.

Adaptability.

Adaptability is a key concept when you're talking about mobile networks and limited airwaves for transmitting signals. Software radio is one technology that can help: it's a radio (or other wireless communicator) that can be programmed to use various RF waveforms. For military and civilian aviation, software radio can help bridge legacy and future technologies and allow for easier upgrades. The biggest impediment is creating affordable radios. And then the next step up is "smart radio" (or "cognitive radio"), which knows how to adapt to the spectral environment and dynamically change modulation and frequency to use unoccupied spectrum that avoids congestion and jamming.

Network-aware applications will also support adaptability. Software and network protocols developed for stationary networks often encounter serious deficiencies when moved to a tactical military environment. So we are looking to create "network-aware" applications that can operate equally well on the base and in the field.

Protocols.

Once different networks are connected, it is the software protocols that let them exchange information and govern how the networks behave. Better protocols are needed, however, to create the kind of airborne networks and net-centric environments envisioned by MITRE's customers.

While the commercial world has been very successful in moving from fixed, wired networks to wireless communications, most of these organizations don't deal with the kinds of environments that the military faces around the world. From the windy deserts of Iraq to the icy mountains of Afghanistan, the Department of Defense's communications equipment must work where there is no infrastructure whatsoever.

The government is planning to roll out the new Internet Protocol Version 6 (IPv6), which will handle a much larger number of network addresses than the current IPv4, provide better security, and make it easier to deploy complex networks. Making the transition from IPv4 to IPv6, however, will require modification or replacement of millions of computers and network devices, as well as software applications that use Internet addresses. There is strong international demand for transitioning to IPv6, motivated largely by the vastly increased address space and the limited ability of IPv4 systems to handle growth in demand. The U.S. Department of Defense plans to start the transition in 2008 and be fully operational in 2012. Other government agencies, including the FAA, are similarly working the IPv6 transition problem.

MITRE researchers are also looking at developing protocols governing information transport for aircraft moving across large distances; better wireless protocols that can predict connectivity, create location awareness and synchronization, and integrate with wired networks; as well as creating disruption-tolerant networks.

Network management.

As the size and complexity of the networks grow, so does the management task. How do you determine what messages get priority? How do you keep information secure? For the airborne network, is there a limited number of clear entry and exit points—and how are they managed?

Managing a wide range of networks that must work together is a big challenge. Most government organizations, including the military, have multiple platforms, a dynamic wireless environment, IP-based networking systems, and non-IP-based legacy systems, plus the need to maintain security and quality of service. Services change frequently, have different release lifecycles, and change independently of the rest of the system.

Most organizations have accepted the constant change and are finding ways to deal with them. For example, the DOD's concept of net-centricity defies pre-planning since they can't determine ahead of time everything they'll need to know to have a working network for soldiers, aviators, and commanders in any situation. The trend is to create systems and protocols that can adapt, wherever and whenever they are deployed, and to make connections that are reliable and secure.

MITRE researchers are exploring a new approach to network design, hypothesizing that the strictly layered architectures that work for fixed wired infrastructures may not be effective in a highly unpredictable mobile network. The alternate approach, cross-layer design, calls for distributing the optimization solution across layers—physical, media access, and routing—so that functionality in different layers is intentionally interrelated. With this approach, any layer can share information with other layers and still be capable of being updated without having to update the entire system.

Security.

Security is an issue that weaves through all areas of wireless networks. It should be built into systems early on so that developers can consider issues such as risk management and bandwidth requirements. The goal is to create a system that obstructs jamming, prevents eavesdropping, reliably maintains its connections, and prevents intrusion.

MITRE is looking at a number of ways to ensure security (see the article on page 11). For example, the "black core" is an IP network that encrypts data coming in and decrypts it going out, so that data is protected throughout its complete journey, instead of being decrypted and reencrypted at each connection point.

Content.

We've touched here on just a portion of the work MITRE is doing in transforming communications. In addition to building the infrastructures that carry communication, we are also addressing the content of the communications—how to make sure people can quickly find what they need to know. For example, we are researching areas such as machine translation, data mining and extraction, matching metadata among systems that use different terminology, data visualization, complex behavior analysis, decision-making, and collaboration tools.

According to Richard Games, chief engineer for the Center for Integrated Intelligence Systems, "If you want to transform communication, you have to look at it holistically, and we are."

For more information, please contact Anne Cady, Richard Games, Ed Palo, Jason Providakes, or Glenn Roberts using the employee directory.

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