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Comms On The Move—Quit Stalling Around!
by Karl Fuchs
Director of Federal Systems Engineering
iDirect Government Technologies

Overcoming key technology barriers that halt military Communications on the Move (COTM)

Military personnel cannot afford to lose connectivity at any moment. Whether cruising on the seas, flying through the air or traveling across the battlefield, high speed, reliable, always-on connectivity is imperative to their success. Increasingly, the military is turning to satellite communications for these critical needs.

Providing this high level of service poses some key technical challenges to satellite providers.
  • Technology must work effectively over ultra-small antennas that can be mounted on mobile vehicles of all sizes
  • The units must belong to a global satellite network, allowing vehicles to automatically connect from anywhere and enabling network operators to easily track assets.
  • Satellite network platforms must meet the military’s stringent security needs
New developments in satellite technology address these challenges. On the ground, advances in spread spectrum technology have enabled efficient transmission through very small antennas. At the same time, enhanced global network management systems allow mobile units to seamlessly connect from anywhere using a dedicated IP address. Advances in security have enabled the cloaking of individual communications and network activity of mobile units.

Improving connectivity transmitted through small antennas
Providing heightened connectivity through small mobile antennas is a challenge. One of the fundamental characteristics of an antenna is its ability to focus a beam to reach the satellite. Generally, larger antennas produce tighter beams that can focus on the satellite more directly. Conversely, sub-one meter antennas—such as those needed for COTM—often spread radio frequency energy over a wide area. In addition, small antennas have low gain characteristics. As a result, higher power is required to ensure the receiving terminal hears the remote over the background noise created when the satellite boosts the signal. Furthermore, as satellite spectrum is limited, the high rate signals coming from small antennas often cause interference with adjacent satellites that may be using the same frequency and polarization.

The challenge for network engineers then becomes to provide broadband connectivity to moving platforms without causing, or being impacted by, adjacent satellite interference. This problem is solved only by spread spectrum technology.

Spread spectrum is a feature hosted on the satellite router that diffuses powerful, high rate signals by “spreading out” the transmissions in such a manner as to minimize the interference to adjacent satellites, but does not limit connectivity to the desired satellite. This feature allows the satellite engineer to overcome virtually any adjacent satellite interference.

Building on this technology, iDirect has developed Direct Sequence Spread Spectrum over TDMA. In Direct Sequence Spread Spectrum, a pseudo noise code is injected into the data stream at a given “chip” rate. The resultant data stream is modulated at a lower spectral density. Using TDMA ensures only one remote in the network ever transmits at a time.

With only one remote transmitting at a time, the total spread factor for a given network can be much lower than is found in CDMA based spread spectrum systems. This innovation enables military organizations to spread signals at a much lower rate than CDMA or CRMA solutions. It also provides more efficient use of ultra small antennas on aircraft, maritime and land-based vehicles.

Equipped with these technologies, mobile units are now being provided with always-on, broadband connectivity of up to T-1 (1.544 megabytes), capable of transmitting videoconferencing to vehicles traveling at high speeds.

Creating seamless global networks
Enabled by spread spectrum technology, COTM is changing the way the military approaches the design and management of mobile networks. In general, IP networks have been designed with the understanding that routers, switches and other core network devices will remain at a fixed location—even if host devices are allowed to enter and leave the network. All of those assumptions change with COTM.

The use of COTM by aircraft and marine vessels, as well as with the increased global mobility of ground units, has resulted in IP routers being transported around the globe and across multiple satellite footprints. This new mobility challenges military network management systems to support global satellite networks in which COTM remotes can be tracked and supported from anywhere in the world.

New satellite networks are being designed from a system-wide perspective. These networks are capable of managing an array of issues. Most importantly, they allow remotes to retain their IP addresses, and such allows network operators to track and manage vehicles across the world. These networks also permit mobile units to automatically reconfigure with different satellite beams across different satellite footprints.

As you can well imagine, switching beams automatically requires sophisticated technology. The remote must be able to determine when, and to which beam, to switch. The new signal must then automatically integrate with the COTM antenna to minimize any loss of connectivity. To determine the appropriate point at which to switch beams, global networks must use precise maps on the position of satellites as well as GPS information gathered from the remote itself. When these remotes switch beams, the system automatically accounts for different QoS profiles as well as for changing data rates.

With the new global satellite networks, military personnel conducting training with a vehicle at Fort Hood, Texas, can load that vehicle onto a ship or aircraft, travel to the Middle East—automatically switching from one satellite beam to another at the correct moment—and hit the ground with the same IP address and the ability to log into the servers at Fort Hood as if they were actually on the ground in Texas.

COTM and network security
As networks become more dynamic and mobile, they are increasingly vulnerable to intrusion from foreign remotes. With military personnel using COTM to relay critical information behind enemy lines, the need for stringent security is obvious. Standards such as FIPS 140-2 encryption and X.509 digital certificates protect inbound and outbound transmissions and ensure that adversaries cannot acquire illicit connections to secure networks.

Going beyond these standards, iDirect Technologies has developed Transmission Security (TRANSEC) for TDMA-based COTM systems. TRANSEC features the ability to give the appearance that the network is in full use at all times. This cloaks communications by prohibiting the enemy from tracking bursts in activity.

COTM pulls ahead
The need for communications on the move in the military is as old as warfare itself. Ancient armies used flags to communicate across the battlefield. During World War II, commanders shouted orders over bulky, hand held walkie-talkies.

Today, COTM is redefining communication on the battlefield. Commanders are able to make decisions using data from multiple locations, such as spy satellites and unmanned vehicles beyond the line of sight. Troops are employing COTM capabilities in conjunction with Wi-Fi or WiMAX, creating mini mobile wireless networks serving allied vehicles within a 500 yard radius.

These and other advances are indications that COTM has become an integral part of military operations, extending net-centric warfare into its final frontier: the battlefield.

Karl Fuchs is the Director of Federal Systems Engineering for iDirect Government Technologies. He can be reached at kfuchs@idirect.net.

For additional information please visit: http://www.idirect.net