Commercial satellites plug bandwidth gap for military satcom
New techniques improve access and security while increasing capacity of existing satellites
- By Terry Costlow
- Mar 02, 2011
Warfighters at the tactical edge rely on timely, highly valuable information, and the Defense Department is increasingly turning to commercial satellite providers to relay those messages and images. To fulfill that mission, communications providers use a range of technologies to increase bandwidth and cram more signals into available links.
A number of trends are driving the demand for bandwidth. Unmanned aerial vehicles are one trend, not because of the thousands in theater but because each carries more sensors with higher resolution than ever before. At the same time, technology exists to push those images and other data inputs directly to dismounted troops.
Meeting NATO's satcom needs is no simple task
That environment considerably changes communications requirements because such missions are not compatible with conventional wired or cellular communication techniques.
"There’s a trend towards using nontethered communications, anything that doesn’t require sustained terrestrial infrastructure,” said Bruce Bennett, director of the Defense Information Systems Agency’s Program Executive Office of Satellite Communications, Teleport and Services.
As satellite communications become increasingly common, military groups are beefing up their capabilities by buying services. Rather than spending millions to launch their own orbiters, military users are using commercial satellites. Agencies deem commercial communications safe and reliable enough for all but the most secure military communications.
“We tend not to view commercial or DOD satellite any differently,” Bennett said. The only real difference is that some government satellites provide protected communications, something commercial providers don’t offer, he added.
Need for speed
Many trends are driving a nearly insatiable demand for more bandwidth. Individual warfighters want all the data that’s available so they can make the best decisions possible. That often includes UAV images. Those images are extremely helpful to warfighters, but graphics can require more than 10 times the bandwidth needed to carry voice communications.
“There’s an increase in the amounts of data with the growing use of UAVs,” said J.J. Shaw, director of naval programs at Inmarsat Government Solutions. Video rates range from 128 kilobits/sec to 274 megabits/sec, far higher than telephony signals, he added. Rates vary depending on resolution and whether the UAV is streaming real-time video or simply sending photos, he said.
Another catalyst for increased satcom is the growing number of receivers in the field. During the past few years, military planners have made a concerted effort to make more data available to warfighters on the ground.
“More and more, the military is striving to get information sharing out to the units operating in the field or in the area of operations,” said Terry Magee, executive vice president at Wavestream.
During the wars in Iraq and Afghanistan, the number of terminals on the ground has grown dramatically. Large antennae that served scores of warfighters have given way to compact antennae that fit in a rucksack.
Though they are compact, those receivers still provide high bandwidth, letting warfighters get high-resolution images or other large files quickly.
“Fly-away VSATs, comms-on-the-move terminals, manpacks and airborne terminals are all examples of the smaller form factors employed,” said Britt Lewis, vice president of marketing and business strategy at Intelsat General. "Many of these are now capable of wideband throughput, whereas in the past these would likely have only benefited from narrowband data rates."
Terminals that communicate via satellite are attractive to military users because they can be set up quickly and moved to new areas just as easily. Shaw cited the Haiti earthquake to highlight the speed with which troops can establish communications in a new theater. The first Broadband Global Area Network terminals were installed just a couple of hours after the earthquake, and the number exceeded 400 in a short period. “BGAN terminals are usually the first on the ground when people are establishing their initial communications network,” Shaw said.
Although putting more communications satellites into orbit is the most straightforward way to increase bandwidth, it’s costly and time consuming. The real key is to boost data rates and develop techniques that let a satellite handle more data channels. The communications industry is providing myriad solutions that give new satellites more capabilities than their predecessors had.
One of the most effective techniques is to use new communications bands that take advantage of the rapid advances in technology to send more data in less time. As with many advances in electronics, the improvements are almost astronomical. Most satellites now use the Ka band.
That technology can transfer data as quickly as 50 megabits/sec.That is more than a 100-fold leap compared to the 492 kilobits/sec rate of the L- and Ku-band satellites that are nearly 90 percent saturated, leaving little room for more signals.
That data rate will give forthcoming satellites the ability to carry many different signals. Voice communications typically take less than 10 kilobits/sec, while many secure Internet transmissions that move at the T-1 line rate of 1.5 megabits/sec can be carried via a Ka-band link.
It’s also cost effective. Satellite and component costs aren’t excessively higher, but the data rates are far better. “I think the military will see Ka band generally as a very good value when they look at the cost per bit,” Shaw said.
Ka-band technology is also being used on dedicated military satellites. The Ka band allowed the first Wideband Global SATCOM satellite to provide more than 10 times the bandwidth of its predecessors. WGS handles many channels, providing built-in data security.
“The WGS satellite system’s multispot beam capability will allow greater bandwidth access and data flow and ensured security,” Magee said. Encryption capabilities are inherent in the system, he added.
Although WGS is a dedicated constellation, observers note that it’s sometimes augmented with commercial communications, underscoring the synergy between commercial and military satellites. “Commercial satcom can provide redundancy to these critical links,” Lewis said.
Although it’s becoming widespread, Ka band is not the ultimate solution. Its signals don’t penetrate rain, fog or other weather conditions nearly as well as other techniques can. That’s prompting specialists to devise techniques that ensure that users get optimal performance. “We’ve developed a series of algorithms that overcome the limitations of the Ka band," Bennett said. "With adaptive coding modulation, we provide feedback and increase or decrease the modulation rate to improve the burn through rate.” Dropping back to the L band is useful during adverse conditions, he said.
Divide and conquer
While new radio schemes increase bandwidth, engineers also have improved techniques for using the bandwidth. For example, Time Division Multiple Access technology lets several users share the same bandwidth by dividing it into multiple time slots.
“Using a deterministic TDMA protocol enables a large number of users to utilize the satellite bandwidth, sending real-time voice, video and data,” said Karl Fuchs, vice president of technology at iDirect Government Technologies, a company that makes routers that work on many satellite bands.
That ability to transmit any type of data brings major benefits. There’s more flexibility, so users don’t have to worry about which satellites are available in their region.
“Most satellites are multimission,” Bennett said. "They can be repurposed based on waveforms to send different things. Much of our equipment uses Internet protocols. We’re using more IP than most of us ever thought we’d use a few years ago.”
Using IP techniques provides substantial benefits. After data has been digitized, it doesn’t matter whether it comes from sensors such as cameras or whether it’s telephony data. The shift to IP also lets the military take advantage of commercial advances. Digital files can be manipulated to reduce their size and impact on network availability.
“IP satellite networks allow for the use of network and link optimization techniques and appliances that provide compression, acceleration and caching functionality that lowers the impact of data transfers across the satellite network,” said Tom Fullerton, senior director of sales technical solutions at Globecomm Systems. “The TDMA architecture provides a more flexible network and lowers overall satellite bandwidth requirements for multiple sites.”
Fullerton added that other advanced signaling protocols have been developed that yield higher bits per hertz without reducing the bit error rate or overall link performance. For example, some managed network providers have adopted second-generation protocols for outbound carriers to increase link efficiency.
Another way to improve efficiency is to move only the information and data that has to be viewed immediately. For example, a lot of bandwidth is necessary to stream images from UAVs in real time. However, all images don’t need to be seen immediately.
“In key locations, they are needed in real time, but elsewhere, signals can be trickle-fed to a database for subsequent analysis,” said Keith Norton, CEO of Paradigm Secure Communications.
Such bandwidth improvements will become available as new satellites go into orbit. Commercial providers are planning a number of launches that will greatly increase military capabilities and capacities.
For example, Intelsat will launch eight new satellites between 2011 and 2013, six of which carry optimized Ku-band mobility coverage. Inmarsat is working with Boeing to develop three satellites that will provide Ka-band communications services, with an initial launch in 2013.
That’s good news to military planners. “A number of companies have indicated plans to enter the communications satellite industry,” said Charlie Edwards, DISA’s deputy program manager of the Commercial Satellite Communications Center. "As with anything, increasing competition should improve the services provided by the industry."
Commercial providers typically distribute the capabilities of their satellite between the military and other users. However, there’s also a push to include specialized or dedicated military equipment. Military organizations are sending their private systems up on commercial satellites. Those combined payloads allow government customers to fill gaps in mission-critical areas and reduce the risks associated with launching their own satellites.
For example, Intelsat and Boeing provided a hosted 20-channel UHF payload on Intelsat’s IS-22 spacecraft. It will give the Australian defense forces continuity of service and augment their existing UHF capacity without the risks and costs of a dedicated satellite.
“The Australian Defence Force's evaluation of the alternative proposal revealed a $150 million savings by using a hosted payload as compared to a free-flyer UHF satellite,” Lewis said.
Those specialized defense systems often include a combination of technologies. Cameras and other sensors could be combined with communications systems, giving military users a range of inputs that otherwise might not be available unless they launch a dedicated satellite.
“Hosted payloads allow integrated sensor and communication suites into single platforms,” Magee said. “This provides greater flexibility out of individual platforms, allowing these platforms to be multimission capable. This provides more bang for the buck, and it reduces exposure, cost and provides more capability to the end-users.”
Although hosted payloads offer many benefits, there are trade-offs. “Operators do not always get full design control for hosted payloads, and as a free flyer, the orbital location may not be optimal and cannot be changed midmission if objectives change,” Norton said.
Although communications traffic is job No. 1, the security of that information is equally important. If communications provide adversaries with any useful information or if enemies can alter even a small piece of data, the benefits evaporate.
There are two major components to security for satellites. One is identical to the security issues of commercial terrestrial communications: encryption. The solutions are also similar. Satellite providers can apply commercial tools such as encryption standards.
“We can utilize everything that’s done on terrestrial systems,” Bennett said. "New encryption standards help improve security and reduce both cost and risk."
The other security challenge is preventing enemies from spying on satellite transmissions. That raises a bunch of security risks because foes can learn a lot by knowing who’s making phone calls, whether a channel is busy and when users switch from unprotected to protected communications.
“Adversaries can glean a lot of knowledge from these transmissions even if they can’t crack the encryption,” Fuchs said. “We’ve worked closely with the National Security Agency and others to ensure that adversaries can’t interpret anything from traffic patterns or see what priority of data is going over the network.”
One technique is to send dummy signals during idle times. That’s simple and effective, but that type of transmission security has its drawbacks.
Transmission security techniques "are utilized to homogenize traffic over time and in intensity so as to protect against conveying important operational information based on observing traffic behavior,” Fullerton said. "Improved security via [transmission security] usually comes at the price of increased bandwidth utilization."
And the challenges go beyond encryption and safeguarding signals to avoid giving away information. Providers must also cope with the same types of hacking issues that plague all companies that provide services on the Internet. For example, attackers will try to overload a communications network so that important messages can’t get through.
“Our overall satellite and terrestrial network routinely addresses approximately 100,000 distributed denial-of-service attacks annually on our network overall, seeking to throttle the throughput of our customer applications,” Lewis said.
In addition, all digital communications use error correction techniques to protect against glitches. Given the importance of most military transmissions, companies are continuously beefing up their efforts.
“We’re always improving our forward-error correction,” Fuchs said. “The latest technique is to use 2-D 16-state forward-error correction.”