The growing importance of VSAT in marine communications underlines the fact that despite its conservative image, shipping has always been at the forefront of adopting the best measn of communication possible. Obviously technological change is only adopted once it has reached a stage where it can meet the unique demands of the maritime industry and in particular prove its reliability and robustness under the harshest of conditions.
Few ship operators or their crews are concerned with the high science and engineering of the satellites themselves but they do need to understand the fundamentals of satellite communications and the radio spectrum.
In essence, a satellite is an intermediate device that enables transmission of data to a ship or receiving data from a ship regardless of the different positions on the surface of the globe of the two parties. The other party can be a shore office or another ship.
All satellites make use of a beam which is a pattern of electromagnetic waves transmitted by the satellite. The transmission from a satellite has a defined pattern and the beam can be wide or narrow covering a large or small area on earth. Using a system of varying frequencies and alignment of antennas onboard the satellite, each satellite can have several beams within which all or most of the satellite’s power is concentrated.
The antennae on the ship are rarely stationary due to the constant movement of the vessel when under way and thus require the dish to be mobile in all dimensions. The dish itself is hidden from view by the radome cover but viewed up close they are sophisticated pieces of equipment with motors and gearing enabling the dish to maintain a lock on the satellite under all but the harshest conditions.
Most ships’ communication systems are required to share channels with others which is perfectly fine for simple communication needs but highly inefficient when dealing with the large quantities of data that some operators generate. This can be overcome by making use of
a very small aperture terminal (VSAT) service. Subscribers to VSAT services are provided with exclusive or semi-exclusive use of satellite channels for sending and receiving voice and data at broadband speeds. Usually they are charged for this on a monthly fixed fee subscription basis (although there may be limits on the data allowed before extra charges apply) as opposed to the rate per Mbit charged when using basic services. This enables a network to be created that permits the transmission of large quantities of data.
Not all ship types or fleet managers need large data flows for commercial reasons but passenger, offshore and container operations frequently do. For passenger vessels this will involve allowing passengers to use, computers, tablets and smart phones as well as providing entertainment services. In the offshore industry it enables survey and other data to be transmitted at will and for container ships there is a need for large amounts of data for stowage plans and customer services.
Early satellite history
As far as shipping is concerned, the satellite communications era began with the establishment in the 1970s of Inmarsat a not-for profit international organisation, set up at the behest of the IMO to provide a satellite communications network for the maritime community. Initially the service was used purely for commercial purposes allowing voice and telex communication with ships at sea equipped with an Inmarsat A terminal.
Without the advent of GMDSS and the mandatory requirement for most ships to be fitted with at least an Inmarsat C terminal, it is doubtful if the marine satellite communications sector would have expanded at anything like the rate it has. By having an Inmarsat terminal on board, ships immediately gained e-mail as a new method of communication.
Early Inmarsat services were described by an alphabetical reference being Inmarsat A, B, C, D and E. When the letter F was reached, the service was renamed Fleet followed by a number (33, 55 or 77) indicating the size of the antenna in centimetres.
Inmarsat-A was the original Inmarsat service and offered analogue FM voice and telex services and, optionally, high speed data services at 56 or 64kbit/s. The service was withdrawn at the end of 2007.
Inmarsat-B provides voice services, telex services, medium speed fax/data services at 9.6kbit/s and high speed data services at 56, 64 or 128kbit/s. Inmarsat-C effectively this is a “satellite telex” terminal with store-and-forward, polling etc. it can handle data and messages up to 32kb in length, transmitted in data packets in ship-to-shore, shore-to-ship and ship-to-ship direction. Message length for Inmarsat Mini C terminals may be smaller. Certain models of Inmarsat-C terminals with GPS are also approved for GMDSS use.
Inmarsat D/D+ is a paging service not regularly used on ships. Inmarsat-E was a global maritime distress alerting service using small EPIRBs that automatically relayed distress messages to maritime Rescue Coordination Centres. This service has been withdrawn.
Inmarsat Fleet 77 offers voice and the choice of mobile ISDN up to 64kbps or an always-on Mobile Packet Data Services (MPDS) for cost effective, virtually global communications. Fleet 77 also meets the distress and safety specifications of the GMDSS for voice communication.
Inmarsat Fleet Broadband was introduced in 2006 when the first of Inmarsat’s i-4 satellites went into service. It offers a shared-channel IP packet switched service of up to 492kbit/s and a streaming-IP service from 32 up to X-Stream data rate. X-Stream delivers the fastest, on demand streaming data rates from a minimum of 384kbit/s up to around 450kbit/s. Most terminals also offer circuit switched Mobile ISDN services at 64kbit/s and even low speed (4.8kbit/s) voice services.
The Fleet service has recently been extended with Inmarsat offering a hybrid service that combines Fleet Broadband with its VSAT services. The first step was XpressLink which worked with Inmarsat’s Ku-Band VSAT and was followed by Fleet Xpress a Ka-band/L-band service that became available once Global Xpress commenced global commercial service. While waiting for all satellites in the Ka-Band constellation to be launched, the company introduced FleetBroadband Xtra (FBX), a regional Global Xpress/FleetBroadband service. Fleet Xpress was launched in 2016 and by June 2017 had secured more than 10,000 ships for the service although not all installations have yet been finalised.
Since the advent of GMDSS, Inmarsat has become a private company and although committed to maintaining the safety services it is no longer focused solely on the marine sector as it once was. Recently the IMO has decided that the GMDSS communications should be opened up to other satellite operators and Iridium Communications has formally submitted a comprehensive application to the IMO via the US government for the provision of mobile satellite communications in the GMDSS. The application is progressing but rather slower than some have hoped but some of the delay could be attributed to delays in the launch of Iridium Next the replacement project that will see Iridium’s existing network replaced by 75 new satellites. The project was announced in 2010 and was initially intended to be completed by 2016 but this has slipped to 2018.
Inmarsat does not market all of its services directly but through service providers who are also able to market the services of other satellite network operators. Because of its GMDSS role, Inmarsat has dominated the marine satellite sector but it is not without competitors in the commercial communications arena.
Among those competing, Iridium Communications was a front runner in voice and light data usage and had the advantage of being able to offer a wider pole to pole coverage that Inmarsat could not match due to the differences in the satellite constellations. Other commercial satellite operators include KVH, Intelsat, SES, Telesat and Thuraya with several smaller regional players also active in the market.
A choice of bands
The radio spectrum is divided into a number of bands some with a wider spread than others. Each of the bands is used for a slightly different purpose. Radio communications on LF, MF, VHF and UHF are all on frequencies below 1GHz which is the point in the spectrum allocated to satellite communications and ship’s radar.
When it comes to communications equipment on board a ship, VSAT mostly requires a choice to be made between systems operating on either C-band or Ku-band frequency. Vessels with modest traffic should opt for Ku-band, which requires less power and smaller antennae. Bigger dishes and more power are needed for the larger bandwidth and better quality of C-band systems.
The attraction of VSAT is that whichever band is chosen the equipment usually comes as part of a lease package with a fixed monthly payment, making for greater control over communication expenditure. On many modern ships the operational element of communication use is expanding rapidly and crews are beginning to expect the kinds of email, internet and calling services that they receive on shore.
Greater bandwidth is now being used to meet the expanding market by making use of the Ka-Band. Inmarsat has invested in five satellites to use Ka-band radio frequencies and deliver mobile broadband speeds of 50Mbps.
L -BAND (1-2 GH)
Almost all of the Inmarsat and all of the Iridium services operate in the part of the radio spectrum labelled as L-band which is very narrow and congested. Being a relatively low frequency, L-band is easier to process, requiring less sophisticated and less expensive RF equipment, and due to a wider beam width, the pointing accuracy of the antenna does not have to be as accurate as the higher bands. Only a small portion (1.3-1.7GHz) of L-Band is allocated to satellite communications on Inmarsat for the Fleet Broadband, Inmarsat-B and C services. L-Band is also used for low earth orbit satellites, military satellites, and terrestrial wireless connections like GSM mobile phones. It is also used as an intermediate frequency for satellite TV where the Ku or Ka band signals are down-converted to L-Band at the antenna.
Although the equipment needed for L-Band communications is not expensive in itself, since there is not much bandwidth available in L-band, it is a costly commodity. For this reason, as the usage of data heavy applications has grown, shipping has turned to more sophisticated technology for commercial communications.
S-BAND (2-4 GHZ)
Used for marine radar systems.
C-BAND (4-8 GHZ)
C-band is typically used by large ships and particularly cruise vessels that require uninterrupted, dedicated, always on connectivity as they move from region to region. The ship operators usually lease segment of satellite bandwidth that is provided to the ships on a full-time basis, providing connections to the Internet, the public telephone networks, and data transmission ashore. C-band is also used for terrestrial microwave links, which can present a problem when vessels come into port and interfere with critical terrestrial links. This has resulted in serious restrictions within 300Km of the coast, requiring terminals to be turned off when coming close to land.
X-BAND (8-12 GHZ)
Used for marine radar systems
KU-BAND (12-18 GHZ)
Ku-Band refers to the lower portion of the K-Band. The “u” comes from a German term referring to “under” whereas the “a” in Ka- Band refers to “above” or the top part of K-Band. Ku-Band is used for most VSAT systems on ships. There is much more bandwidth available in Ku -Band and it is less expensive that C or L-band.
There are no official statistics as to the number of vessels equipped with Ku-Band communications but analysts of the market estimate that around 10,000 vessels is a probable number, indicating that a considerable market exists to be exploited.
The main disadvantage of Ku-Band is rain fade. The wavelength of rain drops coincides with the wavelength of Ku-Band causing the signal to be attenuated during rain showers. This can be overcome by transmitting using extra power. The pointing accuracy of the antennas need to be much tighter than L-Band Inmarsat terminals, due to narrower beam widths, and consequently the terminals need to be more precise and tend to be more expensive.
Ku band coverage is generally by regional spot beams, covering major land areas with TV reception. VSAT Vessels moving from region to region need to change satellite beams, sometimes with no coverage in between beams. In most instances, the satellite terminals and modems can be programmed to automatically switch beams. VSAT Antenna sizes typically range from a standard 1m to 1.5m in diameter for operation in fringe areas and, more recently, as low as 60cm for spread spectrum operation.
KA-BAND (26.5-40 GHZ)
Ka-Band is an extremely high frequency requiring great pointing accuracy and sophisticated RF equipment. Like Ku-band it is susceptible to rain fade. It is commonly used for high definition satellite TV. Ka-Band bandwidth is plentiful and once implemented should be quite inexpensive compared to Ku-Band.
Inmarsat was the first to provide a global Ka-Band VSAT service as its GlobalXpress service came on stream in 2016. The service uses Inmarsat’s fifth generation satellites, the first of which arrived on station in 2014 and entered commercial service in July 2014 powering regional Global Xpress services for Europe, the Middle East, Africa and Asia.
The second Global Xpress satellite – Inmarsat-5 F2 (I-5 F2) – was launched on 1 February 2015and offers services in the Americas and the Atlantic Ocean Region. The third satellite in the constellation was launched in August 2015, with global availability announced at the end of March 2016. Each Inmarsat-5 satellite is expected to have a commercial life of 15 years.
Fleet Xpress, Inmarsat’s hybrid Ka-band/L-band service became operational simulataneous with commercial availability of Global Xpress. Vessels using the service will require a 1m or 60cm Global Xpress antenna and terminal, and a FleetBroadband terminal (either FleetBroadband 500 or Fleet-Broadband 250), that are pre-commissioned on the network to provide quick and easy plug and play deployment. Inmarsat’s partners in delivering Fleet Xpress include Network Innovations, Marlink and Singtel. Additional partners are expected to be added regularly.
As more Ka-Band bandwidth becomes available, there will be several other satellite providers offering Ka-Band VSAT on a more regional basis. Telenor Satellite Broadcasting’s THOR 7 HTS Ka band payload offers 6-9Gbps throughput with up to 25 simultaneously active spot beams. THOR 7 will provide high-powered coverage over the North Sea, the Norwegian Sea, the Red Sea, the Persian Gulf and the Mediterranean. Ka-Sat will cover most of Europe. Yahsat 1b, NewSat Australia, Eutelsat and Avanti Communications will also provide Middle East coverage, offering mariners with strictly regional European and Middle East sailings a Ka-Band alternative to Global Xpress.
With new services in different bands coming on streams, some providers will be operating hybrid services that take advantage of the cheapest network at any given time. The technologies required to facilitate hybrid networks are already well under development and consist of dual-band satellite antennas, Ku and Ka-Band switchable antennas, and the use of equivalent modem/hub infrastructure.
ISM and wi-fi
Most people are familiar with wi-fi as a means for using smart phones and computers and this uses a particular section of the radio spectrum that is actually within the C-Band covered above. There are a number of unlicensed spectrum bands in a variety of areas of the radio spectrum. Often these are referred to as ISM bands - Industrial, Scientific and Medical, and they carry everything from microwave ovens to radio communications. Many of these bands, including the two used for wi-fi are global allocations, although local restrictions may apply for some aspects of their use. The two bands in particular used for wi-fi are the 2.4GHz and 5 GHz bands.
As the 2.4 GHz band becomes more crowded, many users are opting to use the 5 GHz ISM band. This not only provides more spectrum, but it is not as widely used by wi-fi. Many of the 5 GHz wi-fi channels fall outside the accepted ISM unlicensed band and as a result various restrictions are placed on operation at these frequencies.
A system making use of the 5Ghz waveband for vessel communication purposes outside of the VSAT system has been developed by Kongsberg. Maritime Broadband Radio MBR is a smart antenna designed for use in maritime applications where digital high-speed reliable communication and data transfer are desirable. The housing accommodates 60 individual antennae and needs only connections to power and ethernets. The unit is configured from a web interface that also provides the status of the radio and the network. The network administrator can configure and operate units and adjust network resources from any vessel in the network.
The MBR units use highly dynamic beamforming and adaptive power control to secure stable communication in maritime operations with signal obstructions, fading and ranges in excess of 50km depending upon the model chosen. The system can securely carry a diverse array of operational information, from real-time video to system data, and remotely situated teams can work together seamlessly, co-ordinating systems and activities for optimal performance, safety and operational success.
With beamforming the MBR can direct datagrams to the destination as a multi-directional networked wireless system. Supporting IP transmission, the MBR provides a resilient, high-capacity data link for systems that communicate over IP. The use of end-to-end IP connectivity provides cost efficient integration and an interoperable solution for seamless data exchange. The MBR system has been used for testing autonomous vessels in Norwegian waters but the concept has obvious uses beyond this for vessels operating in relatively close contact.