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Communication between ship and shore

⇒ Access to communication services from ship

⇒ Satellite communication

⇒ Communication in Arctic areas

⇒ Iridium performance

⇒ Shore based communication

⇒ New developments

⇒ References

Safety has been a major objective of ship communication systems since the loss of Titanic and the first SOLAS convention in 1914. More recently, ships are becoming more and more dependent on digital communication to operate efficiently. Another important driver is crew welfare. All in all, technical and administrative operations are becoming more reliant on continuous digital communication with shore parties. Some of these existing and emerging requirements are discussed in the MarCom paper (Rødseth Ø.J., Kvamstad B. 2009b). A somewhat older, but more detailed analysis was produced by the MarNIS project (Rødseth Ø.J., Graziosi N., Nicolè R. 2006). Both of these reports are available from the resources section.

Another, more specific requirements discussion is on new communication needs driven by the IMO e-Navigation and EU's e-Maritime initiatives. This is discussed and analysed in the report discussing e-Navigation communication requirements (Rødseth Ø.J., Kvamstad B. 2009b). This is also available from the resources section. The main emphasis here is on direct line of sight communication between ship and shore

Access to communication services from ship

The general problem faced by ships is that they operate in areas where relatively few users exist and where it is expensive to build up a good infrastructure. This applies to many coastal areas as well as on the deep sea.

AMVER plot

A good illustration of this is the AMVER density plot. This illustration is from March 2012 and was produced by AMVER which is operated by the US Coast Guard. The plot shows by colored dots the number of ship reports received in that month in a circa one by one degree area. Blue means 4 or fewer reports while red means more than 50. This can also be used as an indication of ship density in a given area and, thus, the potential number of customers for communication services. Obviously, it will be difficult to find a good business model for providing high capacity telecommunication services, e.g., in the South Pacific Ocean!

Satellite communication

Ships are dependent on satellite communication when out of range of coastal systems. There is a wide range of satellite communication systems available. Very roughly, they can be categorized as below. The band column refers to radio frequency used, most commonly from L-band (1 - 2 GHz) and C-Band (4 - 8 GHz) up to Ku (11.2 - 14.5 GHz) and Ka (26-5 - 40 GHz) Bands. The range refers to IMO's sea areas A1 (coastal VHF range), A2 (medium wave range), A3 (high seas without Arctic) to A4 (Arctic). Bandwidth is typical values, measured in kilobits per second.

System Band Range Bandwidth Comment
Inmarsat C L A3 9.6 kbps, packet oriented GMDSS, Used for short e-mails and messages
Inmarsat Fleet 77/BGAN L A3 128-450 kbps GMDSS (not BGAN yet), supports Internet
Iridium L A4 134 kbps (Open Port) Also coverage in Arctic.
VSAT shared link C, Ku, Ka A1-A3 Any, typical 64-512 kbps. Shared by several users. Coverage varies with system, normally not deep sea.
VSAT dedicated link C, Ku, Ka A1-A3 Any, dependent on price. Dedicated capacity to user. Coverage varies with system and (high) price.
Other (Orbcomm, Globalstar, Thuraya, ARGOS) L, S, C, Ku, Ka A1-A4 Typically low, usually up to telephone. Either bent pipe systems or store and forward.

Inmarsat systems C, Fleet 77 (and probably BGAN soon) are the only systems to satisfy IMO GMDSS (Global Maritime Distress and Safety System) requirements for satellites. However, these do not cover polar regions. Only Iridium covers the full globe, including the Arctic, but with limited bandwidth.

Most civilian systems are built with a certain cost/benefit factor in mind and, hence, represent a tradeoff between coverage, bandwidth, facilities and price. As deep sea areas have relatively few ships, high bandwidth in these areas will normally be very expensive if at all available.

Satellite beam types

To compensate for this, satellite transponders will use different beam appertures to cover different areas of different size. Where there is a high number of users, a number of smaller spot beams are used to deliver as much bandwidth as possible to each paying user. In less densely populated areas, larger beam footprints are used to keep a sufficient number of subscribers in the area. However, the total bandwidth available will generally be the same in each spot, independent of area size. Thus, on the high sea with lower user density, a large beam will be used and the bandwidth (limited by frequencies and modulation used) must be shared between all of these. As an example, Inmarsat global beams use very large footprints covering almost a third of the Earth's surface. A more detailed analysis can be found in the Flagship D1.3 report (Rødseth Ø.J., Kvamstad B., Tjora Å., Drezet F. 2009).

Communication in Arctic areas

Arctic areas are becoming important for oil and gas exploration, fisheries, tourism and more and more for general ship transport as the ice sheet resides. However, communication infrastructure on shore is far between and satellite systems based on geostationary orbits have limited reach as shown in the figure.

Limited reach

The absolute line of sight limit is about 80 degrees north, but due to atmospheric phenomena and satellite constellation geometry, one can experience problems much farther south than this. Problems have also been reported with the reliability of Iridium communication in these areas. Thus, at this point in time the only GMDSS complant emergency communication systems is short or medium wave radio.

Constellation

Even for global beam systems, such as Inmarsat, communication problems occurs on much lower latitudes than 80 degrees when the satellite is far west or east of the communication user. As an example, the figure shows the Inmarsat 4 constallation with three satelittes, F1 to F3. As one can see here, there is a distance between the satelittes of about 120 degrees. This means that at the worst position, a ship will be either 60 degrees west or east of the nearest satellite. This reduces the observed hight over the horizon as shown in the below graph.

If other and closer satellites are available for use, a communication terminal must still be able to switch between them, i.e., adjust the antenna dish direction, and this is not always automatic. Thus, it is important for users to be aware of these issues and employ appropriate technology or operational procedures.

Also, when the satelitte is above the horizon, it will be increasingly suceptible to shadowing effects from nearby mountains and other structures as the latitude increases and the observed hight over horizon decreases. In many Norwegian fjords, ships will not be able to establish digital connections via satellite at all.

Limited reach

Dependent on the frequency used by the satellite and the general capabilities, operators will typically recommend a minimum observed hight over horizon for reliable use. This may vary from 5 degrees for L-band (as, e.g., Inmarsat) to perhaps as much as 20 degrees for the new Ka-Band services. When this is taken into consideration and for the above Inmarsat 4 worst case, it would reduce the maximum latitude for reliable use to 60 degrees North (or South).

These issues have been investigated in the MarCom and MarSafe projects and are further quantified through other ongoing research. The Flagship D1.3 report (Rødseth Ø.J., Kvamstad B., Tjora Å., Drezet F. 2009) gives a more detailed introduction also to these problems.

Iridium performance

The Iridium system is the only that currently provides Internet connectivity in the Arctic regions above 78 degrees north. The MARENOR campaign (Rødseth Ø.J. 2014) measured the performance of Iridium and VSAT systems in areas of the Arctic during several periods in 2014. The referenced article reports from a limited period in April/May 2014 where the ship operated up to 78 degrees north and 20 east. However, much more data has been collected as shown on the figure (January to May 2014).

Iridium measurements

Results from the larger campaign are consistent with those reported in the article: Iridium provides reasonably good service in the areas where no other systems are available, although at a limited bandwidth of about 130 kbps. However, there are important characteristics of the service that need to be taken into account for critical applications. Round trip times are significantly longer than for VSAT and there are relatively frequent communication breaks.

Shore based communication

Communication closer to land is generally less costly than via satellite, but also here the number of subscribers in an area will limit the available services. Thus, one cannot expect to access new generation mobile communication services outside the large ports and cities. This will in particular limit the availability of high speed digital communication services.

Line of sight

Line of sight is another problem for shore based communication systems as illustrated in the graph. It shows range in km as function of antenna hight in m, given that no other effects like diffraction etc. extends or diminishes the range. Although the combined hight of ship and base station antenna adds to the range, it is clear that these systems are severely limited in range.

For safety and operational services this is not a big problem as was documented in the e-Navigation Communication report produced jointly from Efforts, Flagship and MarCom projects in 2009 (Rødseth Ø.J., Kvamstad B. 2009b). The results from this investigation was also published as (Rødseth Ø.J., Kvamstad B. 2009a) and (Rødseth Ø.J., Kleppe B. 2010).


New developments

As mentioned above, ships will often have problems getting access to high bandwidth digital communication at reasonable prices. The main reason for this is that ships operate much of the time in areas with few customers and correspondingly higher prices for the users that are there. As many ships are dependent on satellite systems for much of the voyage, the infrastructure costs tends to be high. In the Arctic region, the normal geostationary satellites will not provide coverage and low Earth systems will probably be too expensive for high bandwidth services. However, new technology and approaches may become available and some of these possibilities have been analysed in the paper on Novel technology (Bekkadal F. 2010). This includes use of mesh type systems to extend shore range and highly elliptical orbit satellites in the Arctic. A more integrated approach to coastal communication is one of the proposals, nicknamed WiCAN (Wireless Coastal Area network).

References

Rødseth Ø.J., Kleppe B. (2010). The Case for a New Digital Communication Service between Ship and Shore, Proceedings of 17. Conference of the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA-AISM): Maximizing the potential of AIS. 22-27 March 2010.

Rødseth Ø.J., Kvamstad B. (2009a). Digital Communication Bandwidth requirements for Future e-Navigation Services, European Journal of Navigation, Vol. 7, No. 1, April 2009.

Fjørtoft K., Kvamstad B., Bekkadal F. (2009). Maritime communication to support safe navigation, TransNav - International Journal on Marine Navigation and Safety of Sea Transportation, Vol. 3, No. 1, pp. 87-92.

Rødseth Ø.J., Kvamstad B. (2009b). The role of communication technology in e-Navigation, MARINTEK Report MT28 F09-095, 5th March 2009.

Bekkadal F. (2010). Novel Maritime Communication Technologies, Mediterranean Microwave Symposium (MMS), 2010, 25-27 Aug. 2010

Rødseth Ø.J., Graziosi N., Nicolè R. (2006). Research report on broadband applications - Part1: State of the art, MarNIS Deliverable D2.2.C-1, 3rd July 2006.

Rødseth Ø.J., Kvamstad B., Tjora Å., Drezet F. (2009). Ship-shore communication requirements, Flagship Deliverable D-D1.3, 31st December 2009.

Rødseth Ø.J. (2014). Internet at Sea: Does it work?, MARINTEK Review No. 2 2014



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Last updated 2015-04-10 by Ø.J.Rødseth @ MARINTEK