Flyaway SATCOM
Written by Adam Baddeley
Rapidly deployable SATCOM—flyaway, suitcase and increasingly manpack—provides a self-evident capability in the SOF inventory. Exactly how this is met however is in a state of flux. Requirements were driving the size of terminals ever downward. Things have now changed with larger aperture dishes now being seen as having greater utility.
Other issues, many interrelated, create further options. Technically there continues to be a move to mesh-based networks, allowing each SATCOM terminal to communicate directly with another. In contrast, legacy SCPC-based hub and spoke systems connect users—the spokes—via a single large hub, but which requires two hops: from one terminal to the hub and then to the second terminal. Both solutions have their adherents and advantages, with many users needing to switch between them according to mission.
The modems that create either network type today largely defy interoperability, which is still largely only within the same manufacturer’s system. DoD is now moving manufacturers to common standards to ease the training and logistics burden.
L-3: SDN PROVIDER
L-3 GCS is currently satisfying USSOCOM’s requirement for terminals under the Ku-band SDN (medium) program. Robert Jacobson, general manager, L-3 GCS, explained, “We have been in continuous delivery of 1 m Hawkeye Lite and sub-1 m Cheetah terminals to USSOCOM since the beginning of the contract in 2007. Our deliveries are backlogged for another four to six months. In our opinion, it has gone great. Reliability has been great; customer satisfaction with the terminals has been great. They have continued to buy the 1 m and sub-1 m in quantities that either meet or exceed our expectations of the program.”
L-3 GCS is releasing several new terminals to the market, which are available in Ku, Ka, X and C-band. Jacobson said, “We offer 1 m to 2.4 m terminals, and we currently have delivered them to customers in three of the four bands. The 2.4 m and 1.6 m versions have recently been ARSTRAT pre-certified for Wideband Global SATCOM [WGS].”
The next solution to go through the certification process is really customer driven. Jacobson reports that most customers requiring X-band are currently using the U.S.-Spanish XTAR constellation. He explained, “We offer to do the accreditation, and it’s up to the customer when they want to fund ARSTRAT.”
Military requirements for ever-smaller terminals are continuing to increase; this includes 1.6 m to 2.4 m terminals. These terminals are downsized if a customer is currently using a larger system today. Jacobson stated that L-3 is currently designing the latest line, the Hawkeye III, with that in mind. “If you told me two years ago that people would want us to do a new line of 2 m and 2.4 m terminals, I would have never believed that, because everyone then wanted smaller and lighter. If you use an antiquated 2.4 m system today, I could now offer you the same throughput on a 2.4 m system, which packs in to 50 percent of the case volume with a similar savings in weight. We have traditionally offered sub-1 m, 1 m and 1.2 m terminals; we are now introducing the Hawkeye III line, which includes a 1.6 m, 2.0 m and 2.4 m because we have a lot of customers who now want that solution.”
L-3 has recently added iDirect’s new Evolution E800 modems, which include a DVB-S2 capability, integrated into the terminal’s chassis. Via an L-band interface port, L-3 terminals can also integrate additional modems such as the MPM 1000, standard in the WIN-T program and offering the Network Centric Waveform.
While the Hawkeye used in SDN(M) was Ku only, the new Hawkeye III will be offered in all four bands. “When I say multiple bands,” Jacobson commented, “it is not a big quad band with a ton of transit cases. We are making our systems interchangeable. You could take the same positioner out with a Ku band kit and take it out tomorrow with an X or Ka-band kit. You minimize your expenses by having multiple RF kits you can deploy with a single system.”
That said there is still an enduring need for some users for an ultra-compact solution—enter the new Panther terminal. Jacobson added, “This is our primary focus today—a robust manpack type terminal in which we are confident is the smallest, lightest weight, highest throughput manpack in the market.” He characterizes the Panther as a BGAN-sized terminal that delivers T1 (1.544 Mbps) data rates. Deliveries to a number of customers began in late 2008.
SWE-DISH
Swe-dish terminals have been a staple among SOF for several years, their compact design lending themselves to rapid, discrete deployment. For its next-generation, CommuniCase Technology (CCT) design, the DataPath-owned company has drawn together requirements from different users to create a modular scalable product, on which all Swe-dish future products will be based, and which can operate across four commercial and military bands: C, Ku, X and Ka.
Exactly how DoD uses those bands is still evolving. Mike Creamer, chief technology officer at Swe-dish, explained, “SOF have tended toward commercial capacity in the past. Now we’re seeing them buy equipment that is capable of transition to WGS. They are not transitioning yet, but they are going to go that way. We think that the trend is toward X-band for smaller terminals, and Ka-band will be used for larger terminals and UAVs. Because Ka is so adversely affected by weather attenuation, it isn’t ideal for small terminals.”
“If you want terminals to be small and light you can’t do everything; there are some limitations due to the laws of physics. As you go to a mesh architecture, then you really need to maximize the performance of small terminals. We are seeing more popularity in our 1.2 m antenna systems than the 90 cm, which was traditionally more popular when used in a hub and spoke configuration.”
CCT provides flexibility; nobody, commercial or military, knows what the future holds. Creamer said, “If users decide that they want a larger antenna, they can come back and buy another antenna; we have 90, 120 and 150 [cm]. If they start off in Ku-band and decide to transition to WGS with X or Ka-band, then come back and buy a new transceiver module. It’s the same with modems. We have different types of modems, and we are expanding that range all the time. We can cover not only iDirect and traditional SCPC models but also DVB RCS and a number of more specialized networks. You never throw the old modem away because we see that a lot of users aren’t transitioning overnight, so we are giving them multiple capabilities. It is not like they have to change forever. If they have to change the original capability, they can change back when they need to.”
One of the most recent developments is the Flyaway version with a 1.2 m antenna. Creamer explained, “That is not as small and light as the Suitcase 120. It’s aimed at a lower-cost terminal, for users who are more interested in cost rather than size and weight. Swe-dish produces the antenna, RF and control system, and DataPath adds the power and baseband and tests the complete terminal. The user can plug his secure phone and transmit either in a TDMA network or SCPC, mesh or hub and spoke; it doesn’t matter.” The system is currently available in Ku-band, adding X and Ka-band in mid-2009.
Satcom on the move (SOTM) is another new capability in the CCT product family. The Swe-dish/Saab—four axis stabilized parabolic SOTM antenna, at 90 cm—is larger by SOTM standards. Creamer explained that this SOTM solution is “just another CCT terminal.” No special waveforms or modulation are needed to communicate with existing terminals. He added, “We have had a lot of interest from the riverine boats and inshore vessels.” The SOTM terminal accesses close to worldwide coverage to almost any commercial Ku-band satellite in service today for up to 10 Mbps broadband communication while moving in rough terrain on land or sea.
Swe-dish’s SOTM solution is built using CCT modules. Creamer explained, “What the user sees, when he sees the user interface, is exactly the same as the suitcase of Flyaway or Drive Away products.” The system is truly interoperable with legacy systems due to fully meeting FCC and worldwide satellite operator requirements in legacy transmission modes, such as SCPC and TDMA, without the need to employ bandwidth hungry and proprietary spread spectrum modulation to overcome terminal deficiencies. For the foreseeable future operation within the common infrastructure is essential for networking with thousands of existing legacy terminals deployed worldwide.
GD SATCOM TECHNOLOGIES
“Some of the biggest challenges we face are getting the size down to 1 m and smaller while still keeping it sufficiently robust for it to deploy around the world,” explained Fred Rieck, product line manager, Warrior, General Dynamics SATCOM Technologies. “The system has to be put up and taken down numerous times, while maintaining repeatable specifications such as data throughput. Any design must reduce the inherent degradation that normal wear and tear causes to a system.”
General Dynamics’ Warrior terminals, widely used across DoD, allows mesh networks to be formed using apertures as low as 0.96 m, through a combination of improvements to power output as well as greater focal efficiency from the antenna. Reductions in size pose challenges both in terms of engineering and from the realm of basic physics. Dr. Robert Hoferer, director of RF engineering, GD SATCOM Technologies, explained, “As the antenna gets smaller, the challenges are increasing both for mechanical packaging as well as RF performance. As it becomes smaller, it is more difficult to design because you have less electrical size to play with, and you have more electrical interaction among the antenna parts. At the same time we have to keep mechanical packaging in mind to keep it light, rugged, stable and rigid. To do that, we use the best materials at hand to meet specific requirements.”
It’s not just developments on the grounds that explain improved performance. Rieck added, “We are also benefiting from higher power satellites. That gives us the ability to have more users at lower power rates, which lends itself to smaller dishes and smaller amplifiers.” Conversely, data throughput from the smaller Warrior dishes has risen to 5 Mbps. Higher efficiencies at the satellite level also ease offaxis emission concerns, allowing antenna size to drop further, without risk of signal interference with nearby satellites. Hoferer added that there has been a trend among the rest of the world to adopt the most demanding standards in this area.
Aiding further shrinkage is the continuing role of Turbo-coding. Fred Rieck explained, “That helps out a lot with smaller antenna sizes. They are able to receive lower strength signals and are still able to decode them.”
Increased compactness has resulted in SATCOM Technologies’ most recent design, the X-Band Microsat. Its phased array, flat panel antenna and transceiver design are currently in the final stages of testing, with deliveries due from June 2009.
Rieck explained, “It looks like a BGAN terminal, but it is able to operate in X-band. It’s an 18-inch square terminal that fits into a rucksack and can be pulled out and operated remotely and can transmit between 1 and 1.544 Mb throughput over a hub-and-spoke network.”
This complements larger Warrior designs currently in service. GD won the Marine Corps’s original Ku-band Support Wide Area Network (SWAN) program in 2007. This was followed up in 2008 by follow-on work to add Ka band operation to the system for use with WGS. The first three systems, the 1.2, 1.8 and the 2.4 trailerized dishes, are now going through accreditation by the Army Space and Missile Defense Command/Army Forces Strategic Command, the agency that is in charge of certification for Ka band communications over WGS. The initial work covers development and testing of proof of concept designs. Once through the ARSTRAT process, a larger contract encompassing over 150 1.2 m, another 40 1.8 m and 40 to 50 2.4 trailerized terminals will follow. Outside the Marine Corps, GD is about halfway through delivery of terminals for Warfighter Information Network-Tactical increment 1/Joint Network Node Lot 10-14, which will continue to 2012.
VIASAT
ViaSat provides many of the key modems used to support DoD SATCOM connectivity amongst rapidly deployable users, being selected by both prime contractors as well as being tasked by the DoD itself to develop standard modems for use across the force.
The company’s LinkWay modem was originally chosen for the JNN Lots 1–9 (Now called WIN-T Increment 1), with over 3,000 modems in the field. For JNN Lot 10, the improved LinkWayS2 has been fielded. Discussing this new modem, Larry Taylor, director Strategic Business Development, ViaSat explained, “We did some very significant upgrades to the LinkWay waveform, including significantly higher burst rates, 8PSK modulation and turbo codes, plus a lot of features that give significantly improved throughput. We also improved the hardware platform itself, including the processor, so that we are no longer limited in terms of how many bits the CPU can crunch. The CPU is now oversized and very powerful in order to accept even more upgrades in the future.”
In a full duplex environment, the LinkWayS2 modem throughput is about 5 Mbps. The final upgrade, easy to upgrade by software in the field or over the air reprogramming, will support full duplex burst rates of 20 Mbps using 8PSK and turbocodes. Other features include TRANSEC, improved IP QoS, internal TCP acceleration, internal IP routers and full compatibility with WGS.
LinkWayS2 also includes a second demodulator that will operate with any DVBS2 broadcast, including receiving the Global Broadcast Service.
ViaSat’s second family of modems, the LinkStar has also been upgraded to the S2 standard including full DVB-S2 with an ACM (Adaptive Coding and Modulation) capability for the broadcast part of the signal.
EBEM
ViaSat was chosen a few years ago to develop the Army’s next generation FDMA (or single channel per carrier) modem, known as the Enhanced Bandwidth Efficient Modem (EBEM) or MD-1366. EBEM contains backward compatible modulation and coding schemes allowing it to operate with many legacy DoD modems, but also incorporates the latest in modulation techniques including turbo codes and advanced modulation of 8 PSK and 16 APSK.
Its AES-256 TRANSEC is endorsed by NSA, and it is WGS certified by DISA. It also features Information Rate Adaptation, also known as ACM. ACM allows the link to always operate at the highest possible throughput configuration for the current link conditions, and automatically adapts the code rate and modulation when link conditions change, such as when rain begins. This allows link margin to be used only to enhance throughput rather than being wasted in clear sky conditions. A Navy version of EBEM allows for error-free antenna handover. EBEM is the basis for a soon-to-be-released military standard, MIL-STD 188-165B. Over 2,500 EBEM modems have been fielded so far.
JIPM
An even more important development, according to Taylor, is the Joint IP Modem (JIPM). In early 2008, ViaSat was awarded the JIPM contract through the prime contractor, Globecomm Systems, under the Worldwide Satellite Systems Program to develop a new Secure DVB/DVB-RCS based hub-spoke modem standard for the DoD. Built to a DISA specification, JIPM is administered through Army PM DCATS. Taylor describes JIPM as combining the best of both the LinkWay and LinkStar network systems families.
Taylor outlined progress so far, as JIPM nears completion. “We are now in the process of installing eight LinkStar hubs around the world in DISA Teleports, something we call pre-JIPM, to begin the training and familiarization with that type of product before being upgraded to a full JIPM capability. Some 70 to 80 percent of that hub is reusable, once we convert to JIPM. Once we complete the development of that modem and it is fielded and proven, then the JIPM air interface belongs to the government and becomes an open standard; MILSTD-188-165B.”
An earlier “165A” standard exists and which Taylor describes as a “benign” standard. He added, “The 165B adds a lot of meat to that specification, including turbocoding, multiple modulation types and TRANSEC. The 165B is reoriented more toward the WGS and its higher bandwidth and dynamic ranges.”
This standard is also being reviewed as a NATO STANAG and could be released as such by mid-2009.
Taylor outlined the background and rationale for the development of JIPM. “For years, different government organizations went different ways to accommodate IP. It was a free-for-all. They ended up with a whole hodge-podge of manufacturers and systems in the field, which is difficult from a training and logistics perspective. Consequently, the government is trying to consolidate into a set of standardized products. Rather than reinventing the wheel, they have taken a commercial standard and are adapting it. In the case of the JIPM, they have focused on the secure DVB and DVB-RCS waveforms, deviating in some areas in order to accommodate their special needs.” One of those is TRANSEC, adding an AES 256 capability.
ViaSat plans to introduce additional features throughout JIPM’s spiral development, including ACM in one of the out-year spirals, and adding a spread spectrum capability to it to allow it to do SOTM. Taylor said, “There are a lot of features that are going into JIPM, not necessarily in the first phase, but the spirals and again in software upgrade spirals.”
ViaSat has produced close to a million modems in its 22-year history and continues to be the leading edge in modem technology. The company also is increasingly moving toward system integration as the demand for complete network systems continues to grow. ♦