COTM demystified

by Clayton Vallabhan | September 9th, 2014

Communications on the move (COTM) works by using stabilised or tracking antennas on vehicles, whether maritime, land or aero-based. The antenna locks onto the satellite and maintains positioning with the satellite to allow users to exchange data, voice and video while the particular vehicle is moving.

COTM isn’t a new concept, according to Tony Sewell, User Terminal Partner Manager, Land, Inmarsat. “It has been used in maritime applications for many years. However, advances in technology are allowing the use of much smaller antennas and higher frequency bands like Ka- band-the frequency which Inmarsat I-5 uses-in order to provide a much larger bandwidth pipe to users on the move,” he says.

COTM, Satcom-on-the-Move (SOTM) or satellite communications on the move are seemingly used interchangeably in the satellite industry, according to Darin Anderson, Director – International Business Development at ThinKom Solutions.
“The basic principle behind COTM is that a platform-vehicle, train, aircraft, or vessel-is equipped with a satellite antenna and is able to establish communication with the satellite of choice and in accordance with the frequency plan to maintain that communication while in motion.
“In motion can mean a variety of things from a vessel being stationary on the water but the antenna system needing to accommodate for the pitch, roll and yaw of the vessel to an aircraft flying at 500 knots an hour, to rail or high-speed rail HSR applications or to an broadcast vehicle or command vehicle, even an SUV that is crossing the desert dunes,” says Anderson.

According to Anderson, COTM has also been applied to the L-Band (1 to 2 GHz) or S- Band (2 to 4GHz) frequency range, sometimes called BGAN technology, working with LEO (low earth orbit) and MEO (medium earth orbit) satellites that cross the skies from horizon to horizon within a fixed period of time. These pay-per-bit business model solutions often have lower capital expense with high operating costs. This relationship is the inverse for SOTM solutions. For SOTM solutions using GEO (geo-stationary satellites) that are in geosynchronous orbit with the earth, the capital expense for the equipment may be higher, but the operational expenses are much lower.

“There are a number of key elements for SOTM antenna systems to work efficiently, they must have the capability to find, lock and track these satellites that are approximately 35,000 kms from the earth and they must maintain the minimum pointing accuracies established by the various regulatory authorities governing the satellite manufactures, namely the ITU, FCC and others,” explains Anderson.

In maritime, vessels today require networks which will support data hungry applications such as HD Voice, video streaming, video conferencing and cloud- based solutions. Commercial operators look to reduce operational costs with increased connectivity. These include advanced weather warnings and port notifications to reduce fuel costs, and engine monitoring sensors to reduce maintenance costs.

Gez Draycott, Senior Manager, Sales Engineering at SES, says that the satellite operator provides services to a number of customers servicing the luxury yacht market in regions such as the Maldives and Seychelles. “These yachts, which can cost around $1 million per year just to maintain, would often demand seamless office/home connectivity. SES works with antenna manufacturers such as Intellian, SeaTel etc., to provide robust solutions to customers on the SES fleet. Antennas such as the Seatel 4009 series (1m) are a popular choice among customers. These allow for quick installation on board and reliable 3-axis stabilised tracking facilities.

“Commercial operators on larger vessels have the luxury of additional real estate on deck. This allows them to operate larger C-band systems, providing added reliability in rainy areas of operation. That said, SES is pushing the boundaries for C-band innovations and has recently activated a service on our NSS-9 satellite at 183E, which uses a 60cm on the West Hemi beam covering Australia, East Asia and North West Pacific regions. The service uses spread spectrum techniques, and allows the customer to operate a very small unit with excellent rain fade properties,” continues Draycott.

Draycott also thinks that aeronautics, while still a relative green field application, presents a good opportunity for airlines to differentiate themselves and increase revenue. The International Air Transport Association (IATA) stated in a recent report (2013) that there will be 331 million new passengers on international flights by 2016. Boeing and Airbus reported that over 7,900 new wide body aircraft will be built between now and 2032. This rise in air travel, and the need for connectivity has driven operators to provide connectivity on-board their fleets.

In the aeronautical field, SES works with a number of providers such as Panasonic, Gogo and Global Eagle (formerly Row44). For these services, SES will work with the vendors to suggest suitable high-power beams providing coverage in the specific regions which cover the commercial flight paths. The settings on the satellite, transponder Saturated Flux Density (SFD) are adjusted to suit the application, as the small antennas on the planes often require a very sensitive transponder for transmission. Antennas, such as the Tecom KuStream 1000 unit are installed on top of the plane body by certified installers, and it is SES’ job to ensure that the service will operate within agreed power levels, providing a stable service for travellers on-board the aircraft.

Anderson explains that the rail markets are proving areas of focus for new antenna designs, but are not without their challenges. “Connectivity to the rails is fuelled by the customer’s expectations to stay connected all the time. Ultra low-profile applications help installation efforts and mitigate bird or debris strike compared to taller domed solutions. However, like the aero markets the certification, installation and integration is a lengthy process. Rail markets are planning the long-term and smart hybrid approaches that bridge terrestrial networks SOTM are mitigating the inherent LOS (line of sight) blockages that may occur in urban environments and tunnels. Rail applications require robust product longevity both in equipment life and duty cycles,” says Anderson.

Further sector-based interest comes from government divisions such as border patrol, military undertakings including command and control operations in conflict zones and broadcast media conducting live video transmissions via satellite news gathering (SNG) vehicles.
Asher Faredi, Product Manager, Land IP, Thuraya, says: “Satellite technology has the potential to significantly broaden the possibilities of connected vehicles, and Thuraya is working closely with car manufacturers to take on the challenge of extending M2M connectivity. Currently, M2M depends mainly on GSM networks, which can be limited in terms of network coverage, especially for vehicles that are required to cross international borders or be deployed in remote locations.

“Backed by our congestion-free satellite coverage, Thuraya is able to provide solutions that address mission-critical needs in rural and remote areas — such as border patrol units that need reliable coverage to transmit video images back to their headquarters, or an emergency response vehicle requiring communications anywhere. The Thuraya IP Voyager is designed to connect at broadband speeds of up to 444kbps while on the move, while the Thuraya Commander is the first ruggedised satellite broadband terminal designed using MIL-SPEC components,” explains Faredi.

So what are COTM’s limitations?
Mobility does introduce some engineering challenges. Draycott says that mobility antennas need to be designed for specific transport which can lead to expensive solutions for customers. Moreover, antennas need to be installed quickly, especially in the case of aeronautical and maritime applications. Taking planes or cargo ships out of service to install antennas can be costly to operators.

“As antennas become smaller, the SES engineering department has to ensure the transmit and receive pattern data is measured and applied to link budget analysis. Uplink power is generally limited for mobile applications, but with improved beam forming technologies we expect this to improve over the coming years. Hardware vendors, such as iDirect and Newtec, are designing improved solutions for mobility applications. Adaptive Modulation and Coding improvements (ACM) ensure throughput is maximised where possible,” says Draycott.

Faredi says some other limitations include obstruction of Line of Sight (LOS), which can be an issue from buildings and trees. Also, unlike L-band satellite connectivity which is more reliable, COTM technologies using Ka- or Ku-band may face interruptions during abnormally harsh weather conditions.

“An important advantage that satellite operators have over GSM service providers is their ability to provide an affordable, uniform and optimised cost for their connectivity, even across international borders, as opposed to expensive roaming charges under cellular coverage. This helps facilitate new business models for the car manufacturers, that are currently not possible with cellular data, as well as enables Thuraya to leverage its position in being able to offer satellite-enabled cellular roaming,” adds Faredi.

With thoughts towards the future of COTM, Sewell from Inmarsat thinks that whether COTM is employed in aero, maritime or land applications, it is clearly one of the biggest growth areas for companies like Inmarsat that are primarily focused on the needs of highly mobile users around the world.

“COTM, and advances in the systems supporting it, are fundamental to the driving needs of people living in a connected world; where connectivity is driving personal and professional productivity regardless of whether you are sitting at home, riding a bus or crossing the oceans on an aeroplane,” says Sewell.

Anderson is of the opinion that HTS (High Throughput Satellites) in Ku and Ka are coming to the global market in grand scale. He says these satellite solutions will afford various markets enhanced capabilities for man-pack and SOTM solutions that may be smaller and lighter in antenna design yet able to achieve greater bandwidth and throughput to meet the increasing demands of use.

Draycott concurs and says that antennas will reduce in size and improve in aesthetics to support greater and more robust connectivity solutions.
“Cloud-based applications will also increase in popularity, allowing users to access data from any location. As mobile networks upgrade from LTE to 4G and 5G, consumers will require additional data, which will perpetuate the growth of data hungry applications. This means that engineers have to be more creative and innovative to ensure that satellite links are designed for robust communications in the most demanding of environments,” concludes Draycott.

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