Comms on the Move
Written by MICHAEL BURNETT
MOBILE MILITARY SEEKS SATELLITE SOLUTIONS, AND COMMUNICATIONS COMPANIES RESPOND.
While mobility and reachback communications are two of the linchpins of modern military operations, bringing those two vital factors together represents a major technological challenge.
Military forces are often on the move, and providing dependable satellite communications to mobile convoys, aircrafts, ships and other vehicles is more challenging than providing service to fixed locations.
As a result, “comms on the move” (COTM) and related mobile satellite services have become a top priority for the Department of Defense, and a wide range of companies are offering products and services to meet those needs.
Inmarsat, for example, provides much of this comms on the move capability through products specially designed to provide satellite service to mobile units. Service providers like Stratos Government Services Inc. (SGSI) provide Broadband Global Area Network (BGAN) service enabled by Inmarsat, adding services to the basic BGAN capability to boost utility for their military customers.
“These services provide users with cost control, firewall management, information assurance, full traffic information, high security options, easy VPN access, messaging services and full IP range, including SKYPIPE TCP/IP accelerator for faster Internet connections and file transfer,” said SGSI President Bob Roe.
The BGAN land mobile satellite systems use ruggedized terminals weighing 3 kilograms for voice, data and video communications, Roe explained. The data transfer occurs at speeds of up to 492 kbps. Users can control costs with the Mobile Packet Data Service, which charges them only for data packets transmitted and received. SGSI adds a SecureComms gateway to BGAN voice services and NET Shout technology for simultaneous secure voice calls.
The company also offers specialized solutions for maritime and aviation platforms.
“In the maritime sector, the most exciting new development is Inmarsat Fleet- Broadband from Stratos,” Roe declared. “FleetBroadband provides cost-effective, high-speed data and voice communications—for both primary and backup connectivity— at speeds up to 432 kbps, regardless of the vessel’s location.”
FleetBroadband services, available beginning this fall, use compact directional antennas of various sizes fit for different types of ships. To help save space, manufacturers have designed any antennas above deck to be smaller than existing antennas deployed in the Navy. SGSI anticipates quick and easy integration with existing networks, since Fleetbroadband relies on Internet Protocol.
“In the aviation segment, the most impressive new mobile satellite service is Inmarsat SwiftBroadband from Stratos, which will be commercially available in October,” Roe continued. “It is the first network delivering high-speed mobile data services to aeronautical customers.”
WARRIOR TESTING
A major player in this field of mobile communications is General Dynamics SATCOM Technologies, which offers an array of Ku-band on-the-move satellite communications terminals.
The company this spring received an Army contract to provide one of its Warrior Model 20-20 Satcom-on-the Move antenna systems for verification and testing, with additional purchases to follow successful tests. The total value of the award could reach $28 million over three years.
The General Dynamics-designed and -manufactured equipment transmits and receives data at speeds up to 1.54 Mbps in Ku-band, giving unit commanders robust satellite communications in moving vehicles, providing unequaled mobile access to a broad spectrum of information services including video, data and imagery. The terminals track satellites very accurately using a combination of integral satellite-beacon receivers, gyro stabilization and inertial measurement units.
“Reliable, easy-to-deploy communications products are vital to supporting tactical missions,” said Gary Kanipe, vice president of General Dynamics SATCOM Technologies. “General Dynamics is the original equipment manufacturer for the VertexRSI antennas and electronic products that comprise these terminals, ensuring a high-quality, reliable SATCOM-on-themove communications solution for our customers.”
The contract was awarded through the Program Manager Warfighter Information Network-Tactical, under the contracting authority of the Communications and Electronics Command.
The Warrior Model 20-20 SOTM system includes a 20-inch diameter antenna, antenna controller, servo system, inertial reference unit, radome, power amplifier, Low Noise Amplifier, up/down converters and ancillary equipment. The SOTM antenna system will be installed on Humvees, Bradley Fighting Vehicles or Stryker Infantry Combat Vehicles.
SIZE ISSUES
Small antennas are needed in mobile systems not only to save space, but also because they reduce the profile of land vehicles, making the communications system less of a target for enemy forces.
iDirect has developed iDirect Spread Spectrum to overcome the limitations of small antennas, according to Karl Fuchs, iDirect director of federal systems engineering.
“Two things are happening when you are moving,” Fuchs noted. “When you have a fixed terminal, the antenna is fixed and can be pointed precisely at one particular satellite with a very specific polarization. That has been done for many years and people have gotten pretty good at that. But when you have a vehicle moving, you have to have some type of stabilization mechanism for this antenna. The antenna platform is going to be moving, but it still must remain locked on a given satellite. That’s a lot of the hard work that goes into antenna design.”
iDirect, which manufactures a variety of satellite communications hardware, has worked to overcome the limitations of physics when designing small antennas. Traditional large antennas have a sharp focus, and can point to satellites in geosynchronous orbit over the United States. Those satellites are spaced about 2 degrees apart from each other. Services that use the satellites, which operate at a shallow angle, must take care not to interfere with each other, Fuchs explained.
“All of these satellites are reusing the exact same frequencies. There is limited spectrum that can be used for satellite communications,” Fuchs remarked.
“When you have a big antenna with a very sharp focus and you are transmitting to a particular satellite, almost all of your energy hits the satellite you intend. Very little bleeds off to the side,” he added. “As you decrease the size of the antenna, the focus gets sloppier and sloppier. When you transmit off from a small antenna, a good deal of the energy that you are transmitting hits the intended satellite but some of it bleeds off to the adjacent satellites.”
Some of this adjacent satellite interference is acceptable, Fuchs continued, but too much interferes with the signals of others. Spreading the waveform of the signal with a technology like iDirect Spread Spectrum helps to eliminate adjacent satellite interference.
iDirect manufactures all of the hardware necessary to ensure satellite communications— from the hub chassis and the line cards for large teleports, which have big antennas often 12 meters or larger in diameter. It also manufactures remote equipment using smaller antennas of 1.2 meters or 1.8 meters. Antenna mounted on trucks or aircraft may have to be even more compact, as small as 60 centimeters.
“When you talk about comms on the move, you have to think about this from a systemwide perspective,” Fuchs observed. “iDirect provides the hub gear as well as the network management system required to support both stationary and mobile terminals. Mobile terminals move from the west coast of Europe to the east coast of the United States. All of this has to be managed from one platform and handoffs have to be done from one satellite to another. iDirect has that technology.”
HIGHER BANDWIDTH
As dependency on comms on the move grows, the military will turn to it for increasingly high bandwidth applications.
While the L-band satellite frequencies used by BGAN are suitable for voice, data and other applications, L-band is about half the speed of Ku-band satellite services, which offer the possibility of more robust service.
Americom Government Services has been marketing the advantages of Ku-band comms on the move service in preference to L-band service. L-band solutions are used in a wide variety of applications, but the applications have very quickly outgrown the performance capabilities of Lband, according to Larry Simon, Americom Government Services director of business development.
“With our Ku-band comms on the move initiative, we are trying to make available to the DoD a higher performance on the move capability that is substantially cheaper than L-band,” Simon said.
“L-band has very limited bandwidth and there are only a couple of satellites supporting it,” he continued. “Ku-band, on the other hand, has a lot of satellites and a lot of transponders and thus a lot more bandwidth. Given the difference in the amount of bandwidth available, it is possible to provide a more robust infrastructure that allows higher performance at a better price.”
Americom has partnered with ViaSat, providing satellite service that utilizes ViaSat technology, including the company’s ArcLight modem.
“Each aircraft or ship would use a different type of antenna, but a common modem—a ViaSat Arclight modem. By using a common modem, all of those different types of applications can share an infrastructure and communicate amongst one another,” Simon explained.
L-band has proven its worth for low-bandwidth applications, Simon acknowledged, and is quite reliable, meaning that it is here to stay. DoD has been making movement toward rolling out Ku-band comms on the move for more demanding applications, however.
The Army Warfighter Information Network-Tactical (WIN-T) program has been using Ku-band utilizing its own modem and antenna. So WIN-T is using the same service with specific equipment, which will likely spur further use of Ku-band through DoD and lead to demands for commercial equipment, Simon said.
“They will slowly adopt the technology and get it out and then begin to apply it to the applications that the Lband solutions aren’t serving,” Simon commented. “Those applications are primarily surveillance and reconnaissance applications. They have a lot of video and data. They have a lot of traffic, which the higher performance Ku-band services well.”
INTEGRATING CAPABILITIES
Integrators such as Telos Corp.’s Xacta subsidiary concentrate on finding the best parts to make up a total comms on the move solution while adding additional capabilities to the service.
For example, the company evaluated antenna manufacturers very carefully when looking for a COTM antenna for convoy vehicles, said Tom Badders, business development director for Xacta Secure Networks.
“You can have a vehicle either by itself or in a convoy in a deployed environment with a satellite antenna on its roof, which is extremely large, so it’s a target. This could be a dish or a dome or whatever. So we found a phased array antenna system that is very low profile. It is a flat antenna that stands only 5 inches off the top of the vehicle. It’s very difficult to see if you are the enemy,” Badders reported.
The antenna provides voice, video and data capabilities via satellite, but Xacta sought ways to boost their offering by adding mesh networks and voice radio to Ku-band service.
“To add more capabilities, we integrate a wireless mesh system within the vehicle, creating a mesh network in the vehicle and also providing the capability of adding mesh nodes to additional vehicles within a convoy. So multiple vehicles, 10 to 20 or more vehicles, become a moving network in itself,” Badders described.
“That gives that convoy connectivity to the outside world via satellite— whether it is to home base or to another regiment’s headquarters. The mesh network also gives them the capability to communicate amongst each other with voice or data or video within the convoy,” he added.
At the convoy’s next location, the mesh network could serve as the military’s tactical operations center network, freeing up satellite bandwidth for other purposes.
Multiple disparate voice radios over IP provide a means for emergency response networks to integrate different radios from multiple jurisdictions. The various radios would be able to communicate over the IP network, even if they were incompatible originally.
Xacta incorporates special capabilities developed from companies like RaySat, which has developed a phased array antenna system that can capture signals from inclined orbit satellites, thereby boosting throughput.
“When a satellite starts to reach its end of life, instead of dying and going away, it starts to fall out of its orbit toward the earth,” Badders said. “Generally most Ku-band satellite antennas cannot lock onto that. Our selected antenna is a phased array system that can lock on to inclined orbit satellite, which gives you longer capability for connections in a specific region.”
In addition, Xacta is looking toward the future when the military also may use more X-band frequencies. Currently, X-band antennas are too large for comms on the move in aircraft or land vehicles, but advances in technology may one day shrink them.
But more ships are using X-band systems despite the large antennas.
“X-band provides a lot of capability that Ku-band doesn’t,” Badders stated. “It runs at a frequency that is less susceptible to rain and fog and sand and so on. The Ku-band may have problems maintaining connectivity in heavy rain or sand. There is more bandwidth available in X-band.” ♦
