satellite WIN-T communications
The US Army is overhauling its communications via the introduction of the conventional and satellite WIN-T communications network. This will employ the Network Centric Waveform. (Us Army)

Satellite Communications or ‘SATCOM’ is nothing short of a communications miracle, offering high bandwidths over long ranges. Unsurprisingly, militaries around the world want this capability on their platforms, particularly their vehicles.

The benefits afforded to military operations by SATCOM are well documented: They include the ability to send relatively large quantities of data traffic, not to mention voice communications, particularly in comparison to High Frequency (HF) radio communications in the three to 30 Megahertz (MHz) part of the radio spectrum. HF can achieve intercontinental ranges, but often at the expense of bandwidth which can be limited to say the least. SATCOM’s ability to handle large quantities of communication traffic across intercontinental range has, unsurprisingly, led to a high demand from militaries, particularly land and naval forces, across the world, which appreciate the capability such communications offer in terms of bandwidth and range. The upshot of this is that SATCOM is now becoming increasingly ubiquitous on the battlefield, and is even being found equipping troops in direct contact with the enemy at the forward line of the battle area.

US Army
Staying in touch, while also handling large volumes of voice and data traffic, including imagery, is proving to be increasingly important for troops on the move, with the necessity to equip their vehicles to this end. (US Army)

Currently, dismounted troops can employ SATCOM in the form of antennae and SATCOM terminals to enable such communications. They can also use military SATCOM appliqués, such as Spectra Group’s SlingShot system, which enables conventional military Very High Frequency/Ultra High Frequency (V/UHF) tactical radios operating in the 30-300MHz and 300MHz to three gigahertz (GHz) sections of the radio spectrum to employ L-band (one to two gigahertz) SATCOM. However, there is now a growing need to ensure that not only dismounted troops can use SATCOM, but also their vehicles, and indeed other vehicles on the battlefield, and that these vehicles can do so while travelling. This has led to a corresponding effort within the military SATCOM domain to develop SATCOM-On-The-Move (SOTM) capabilities for land forces.

The benefits offered by SATCOM are obvious: Vehicles equipped with such technology will no longer be constrained by the limitations of their organic V/UHF vehicular radios. V/UHF communications have clear advantages for land forces in that they can handle potentially large quantities of data in the in the order of circa 100 kilobits-per-second (kbps) for vehicular radios such as Aselsan’s PRC/VRC-9661 V/UHF Software Defined Radio (SDR). Yet, the ability of such transceivers to handle data communications comes at the cost of range. All V/UHF radios are limited by a line-of-sight range. Put simply, at sea level, across a flat space, for a person carrying a V/UHF standing on the ground, this distance is typically around three miles (4.7 kilometres) although this increases the higher the person is placed, if they are standing on a tower for instance. The propagation of V/UHF radio is further complicated when obstacles such as hills, mountains and buildings get in the way of transmissions. This is why military tactical radios uses Mobile Ad Hoc Networking, or ‘MANET’, to skip from one radio to another, like a frog jumping across lily pads in pond, for communications to reach their intended recipient. SATCOM, and the intercontinental ranges which it can achieve by bouncing off a dish in space, thus greatly increasing communications’ range as well as data rates. This is a major consideration when land forces may be operating in vast theatres such as deserts. For example, the French armed forces is engaged in Operation BARKHANE, an anti-insurgency operation in the Sahel region of Africa directed against violent Islamist organisations encompassing areas of Burkhina Faso, Chad, Mali, Mauritania and Niger. Given the size of such a theatre, the benefits which SATCOM offers to dismounted forces, and mobile units alike, are clear.

Design Criteria

Several design criteria are essential when developing SOTM terminals for military vehicles. These include the provision of high data rate communications combined with a low physical footprint and the ability to operate in harsh environmental conditions, coupled with extreme reliability and constant availability; the latter feature is to ensure that vehicles are always connected to their satellites. Other considerations include spectrum, notes Yuval Dagan, deputy director of marketing and sales at Israel Aerospace Industries’ (IAI) ELTA division. Spectrum is a finite resource. The more users crowding a particular segment of the spectrum, such as X-band (7.9-8.4GHz for uplink/7.25-7.75GHz for downlink) for example, the less spectrum there is to go around for each individual user. As one can imagine, in large multinational operations across large land areas, such as the US-led intervention in Afghanistan last decade, SATCOM, and hence spectrum remained in high demand.

This demanding for spectrum can be mitigated to an extent by using SATCOM systems which use the spectrum in an efficient and intelligent way, minimising their electronic footprint to this end. “As more and more SATCOM systems occupy the spectrum, the resource is becoming scarce; this is where spectral efficiency has become a very significant factor that allows operating SOTM in dense spectrum, thus providing high demand communication availability,” observes Mr. Dagan. Also increasingly important, he notes, is the ability to protect SOTM terminals against cyber attacks, alongside their resistance to conventional electronic countermeasures. IAI provide two notable SOTM products, chiefly their EL/K-1895 SATCOM terminal for ground forces and vehicles, and their EL/K-1882 terminal for ground platforms.

Yet alongside the need to ensure that spectrum is managed sensibly and in a robust fashion, the ability to rapidly connect to a satellite, and to maintain that communications link, is also a vital design criteria for SOTM terminals, observes Anthony Griser, business manager for General Dynamics’ SATCOM technologies’ SATCOM-on-the-move product line. “The critical design criteria (for) SOTM is … the terminal’s ability to recognise the correct satellite, lock on to that satellite, and maintain that lock through vehicle manoeuvres and line-of-site blockages (such as elevated terrain).” He adds that the firm’s X-band, Ku-band (14GHz for uplink/10.9-12.75GHz for downlink) and Ka-band (26.5-40GHz for uplink/18-20GHz for downlink) SATCOM products can “connect to a satellite and maintain communications, even during aggressive vehicle manoeuvres.” Among other users, General Dynamics provides its products to the US Army. 

General Dynamics
General Dynamics provides a range of SOTM products to a number of users, including the US military. The SATCOM antenna is clearly visible in the vehicle in the front of the pictured convoy. (General Dynamics)

Software

Yet hardware is only part of the story. Software has its important part to play in SOTM system design, in particular, the waveforms which enable SATCOM to be performed. For the uninitiated, a waveform is essentially software which instructs the hardware of a SATCOM terminal to operate using certain parameters to ensure that communications with a satellite can be maintained, and that voice and data traffic can be handled by the terminal in the fashion desired by the user. L-3 Linkabit provides SOTM terminals which employ the US military’s non-proprietary Network Centric Waveform (NCW). This is a Ka/Ku-band waveform which is used across the US Army’s WIN-T (Warfighter Information Network-Tactical) conventional and SATCOM communications network, which is currently being rolled out across the force in several increments. One feature of the NCW, Elissa Seidenglanz, president of L-3 Linkabit, tells Armada, is that it “maximizes bandwidth/power efficiency at the satellite, resulting in larger network terminal populations (number of users utilizing a specific SATCOM network) and lower operational costs as compared to conventional IP (Internet Protocol) over SATCOM systems.” Ms. Seidenglanz continues that the NCW is relatively ‘agnostic’ regarding the SATCOM terminals which can use it. Moreover, in terms of constellations which NCW-equipped terminals can access, they include the US Department of Defence (DoD)/Australian DoD Wide Global SATCOM constellation developed by Boeing, Ms. Seidenglanz adds. 

satellite WIN-T communications
The US Army is overhauling its communications via the introduction of the conventional and satellite WIN-T communications network. This will employ the Network Centric Waveform. (Us Army)

Agnosticism

A level of agnosticism is important in SATCOM. As noted above, some solutions, such as SlingShot are able to connect to an existing tactical radio and to then provide SATCOM. This is also the case, for example, with Inmarsat’s L-band SOTM product. According to Andy Start, president of Inmarsat’s global government products, the L-band SOTM can connect to a conventional V/UHF tactical radio, and then allow that radio to perform communications across Inmarsat’s L-band Inmarat-4 network. The ‘secret sauce’ of this product is the data rates that it offers. These can include data rates of up to 300kbps, which will allow the streaming of video imagery in real time, enabling it to be used to carry Unmanned Aerial Vehicle reconnaissance imagery, for example. Mr. Start states that this product is ideal for man-pack or vehicular applications. Available in both VHF and UHF variants, according to the type of tactical radio it will accompany, the L-band SOTM can “also act as a bridge for the whole tactical radio net.” What this means in practice is that the L-band SOTM can behave as the gateway to allow a tactical radio network to send traffic across intercontinental ranges.

Beyond the firms discussed above, other companies involved in SOTM provision include Airbus’ defence and space subsidiary. According to Paul Millington, the head of government communications satellite strategy at the company, they provide SOTM terminals for mobile land communications such as its MobilePatrol products. Moreover, the firm’s Proteus Software Defined Radio modems allow standard military tactical radios to access a SATCOM gateway. Beyond specific products, the firm also offers SATCOM services to military user. These include “mobile baseband capability for users to either access our Global Interconnect Network in the tactical environment or via their own network,” Mr. Millington continues. The company has provided its SATCOM products to a number of customers around the world including Australia, Canada, Chile, the Czech Republic, Germany, France, NATO (North Atlantic Treaty Organisation), the Netherlands, Portugal, Saudi Arabia, Singapore, Slovenia, Sweden, the UK and the United Arab Emirates. Mr. Millington emphasises that the firm’s SATCOM products are customisable according to the user’s requirements. “There is a standard production specification but elements can be changed, for example, the frequency and RF (Radio Frequency) component mix or (accompanying) antennae or high power amplifiers … to respond to customers specific requirements.”

Thales’ SOTM products
Thales’ SOTM products include its SATMOVE products which are in service with the French armed forces. They enable communications with X-band satellite constellations, with the company also working on a Ka-band version of these products. (Thales)

Like Airbus, Thales has been involved in the SOTM domain for a number of years, and commenced the manufacture of its SATMOVE terminals to this end in 2009, the company told Armada via a written statement. These terminals are currently in service with the French armed forces and have been deployed in support of the ongoing military operations which they are performing in the Sahel (see above). Currently, Thales provides its SATMOVE product in an X-band. X-band SATCOM is reserved by the International Telecommunications Union, the United Nations organisation which supervises the allocation of radio spectrum, for use by the military. The X-band design of the SATMOVE terminals enables the French armed forces to use the Syracuse-3 constellation which provides SATCOM to the French armed forces. The Thales statement adds that a Ka-band version of the SATMOVE terminal is currently in development which “should enter production in the near future”. Military SATCOM is migrating to higher frequency levels, notably Ka-band, which is due to congestion in other SATCOM bands, such as X-band, and also the need to accommodate increasingly smaller antenna, particularly on vehicles, which require such antennae in order to help reduce a vehicle’s visual signature as much as possible.

Harris GNOMAD
Harris’ SOTM products include its GNOMAD product line. Among the capabilities offered by these products include their ability to operate with the Single Channel Ground and Airborne Radio System to greatly extend the range of this conventional tactical radio waveform. (Harris)

While there is a noticeable demand for the provision of SOTM for dismounted troops and their vehicles, commanders also need similar services to enable them to remain aware of what is happening in the battle. Rob Semple of Harris states that, “The way militaries conduct operations changes daily and providing leaders the information they need to make timely and correct decisions become more paramount. Once a leader is disconnected from a fixed Command Post (CP) they still require situational awareness, and command and control while operating physically displaced from their CP.”

The Marketplace

Airbus is bullish regarding the future demand for SOTM. Mr. Millington notes that the firms existing, and potential, customers “want to have the best possible knowledge and awareness of the environment surrounding them. They want this intelligence as quickly as it is available and sometimes this can be while on the move.” Asked what technological requirements we may see for future SOTM technology, Mr. Millington says “anything that improves the performance, flexibility and the ability (of SOTM) to integrate with other bearer networks, carrying the traffic, will be important. Bandwidth will also be crucial because trends today show that demand for data services has surpassed the demand for voice services, in turn putting pressure on the demand for bandwidth.”

SOTM technology is also changing thanks to advances in electronics. As noted above, antenna size is always a significant consideration, particularly as regards vehicles where the need to reduce visual signature is particularly important. The reduction in the size of SATCOM antennae has benefitted from the increasing miniaturisation of electronics, notably Moore’s Law, the observation of Gordon Moore, co-founder of the Intel chip manufacturing corporation, that the number of transistors that can be housed on a single chip doubles every two year. This has the added consequence of reducing circuit size, and hence the physical size of electronic components. This is feeding into the migration for SOTM to antennae that retains more of the appearance of a thin tile, rather than a bulky antenna, Harris’ Mr. Semple observes. He goes on to note that electronically scanned arrays where SATCOM RF beams can be electronically ‘moved’ to reach their satellite, rather than having to physically move the SATCOM antenna also offer promise. This is a particularly interesting development for SOTM where a vehicle’s antenna has to physically move to ensure that contact is maintained with the satellite, while the vehicle itself is in motion. Enabling this function to be done electronically will reduce the number of moving parts, and hence incidences of failure, for SOTM equipment. The demand for SOTM shows little signs of abating.

The ability to access SATCOM while mobile, as well as stationary, is a capability which militaries around the world will increasingly take for granted, to the extent that they may wonder how they managed without this capability in the first place. For Ms. Seidenglanz the pressure to ensure interoperability between militaries deployed in multinational operations of the sort which have been relatively commonplace over the past two decades, particularly where Western-led interventions in the Afghanistan, the Balkans and the Middle East are concerned, is only likely to increase the demand for SOTM, and SATCOM in general. This is because the need to communicate and to share information between participants shows no signs of reducing.

by Thomas Withington