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The low-frequency L-band spectrum (1-2GHz) for satellite transmissions is part of a selection of services labelled ‘Mobile Satellite Services’ (MSS). These services offer satellite bandwidth on a ‘pay as you go’ basis and have been the most popular form of voice and data connectivity in the maritime world since before the turn of the century.
Bandwidth spectrum is limited in L-band, so operational costs can be higher than VSAT, although equipment costs can be correspondingly lower. Likewise, L-band services are less cost-predictable than VSAT, and stories of ‘bill shock’ have been common in the past, where users have to pay tens of thousands of dollars more than expected because usage wasn’t monitored, i.e., a large Windows update had been downloaded over the air.
However, L-band is prized in the maritime community as a medium for transmitting and receiving data/communications even in rainy, foggy and stormy conditions. Likewise, the global nature of L-band networks from Inmarsat and Iridium means that ships can communicate using a single service. The trade-off here, is the higher operational costs and the relatively low connectivity speeds of L-band.
In its favour though, is the fact that L-band terminals are much smaller than VSAT antennas, so can be deployed on almost any size and type of vessel, from yachts through to super tankers. In addition to L-band’s all-weather ability, the hardware is ideal for maritime use also, because less pointing accuracy is required from the antennas, so a stable link is easier to achieve.
While the limitations of L-band restrict high dependence on digital applications for smart shipping, the frequency will continue to play a significant role in the future. L-band terminals are used to augment VSAT installations, coming into action when the primary Ka-, Ku- or C-band system is not available due to weather conditions or lack of service in specific regions.
The L-band Inmarsat FleetBroadband is an integral part of Inmarsat’s Fleet Xpress service, which also uses Ka-band satellites. Additionally, the new Iridium Certus L-band service is expected to become a very popular secondary channel on VSAT networks, thanks to its pole-to-pole global coverage, which will ensure a ship is connected literally anywhere in the world.