Handbook of best practices

4. Post-deployment procedures (CNRS, IEO, CNR, INGV)
4.1 Data transfer
Several methods can be used for data transfer. The system used to do so is heavily
dependent on platform type, location, economic cost, power consumption and desired
frequency.
For this purpose, one (or more if the transmission system is redundant) can be adopted:
• Satellite: this system can be considered “universal” as satellite has worldwide
coverage, avoiding the platform location issue. This system is also very reliable, but
since satellite transmission is normally paid based on bandwidth consumption it can
be very expensive or limit the amount of transmitted data.
• Radio: the benefits of using this system are they low power consumption and the
almost unlimited amount of data that can be transferred. Con for this system is that
you need a line of sight or repeaters in order to be able to transfer data. It has to be
taken into account that two different band types of radio frequency can be used, free
or licensed band. Free band is accessible to everybody, but since everybody can
make use of this part of the radio electric spectrum you may face interferences, even
leading in data loss. The use of licensed band is restricted so interference is avoided,
but payment may be required. Usually for research purposes it is free of charge, but
this is country legislated so contacting your country radio electric spectrum control
managers is a must.
• Mobile broadband: the development of 3G/4G networks facilitates the access to
these technologies for data transmission. Quite robust, reliable and affordable, its
main limitation is the geographic availability, where in off shore observatories the
coverage of this network is practically zero.
• WiMAX: belongs to the 4G technological family and as the more known Wi-Fi allows
wireless communication between two devices through electromagnetic waves. The
maximum speed and range of the WiMax connections depend on the version of the
standard used in accordance with the IEEE 802.16 family of standards. The latest
version, known as WiMAX IEEE 802.16m or WiMAX Release 2.0, allows theoretical
speeds of up to 1 Gbit/s for users in fixed locations, and 365 Mbit/s for mobile users.
The theoretical range goes from 15km for mobile users to 50km for users at fixed
locations. These are theoretical maximum speeds and ranges and the actual
maximum depends on the number of users simultaneously connected to the same
access point and other factors, which make download speeds and real ranges in
practice tend to be lower than the theoretical maximum. With high transfer speeds,
the main handicap for this solution to be adopted is its range since many
observatories are placed further than the actual range.The link between observatory
buoy and ship of opportunity is a good solution to avoid disturbing the buoy and
transmit more data than satellite communication link. A dedicated task was planned
by FixO3 proposal but cancelled during the negociation after budget reduction.
• Undersea cable: this is the most robust solution but also probably the most
expensive and difficult to implement. It also allows an almost unlimited bandwidth, but
installation and maintenance is a long process since for long cable runs the price is
prohibitive and environmental issues may arise in any cable length, requiring
permission from authorities. EMSO has addressed these topics. This will be limited to
sites of high interest where multidisciplinarity arguments converge to a consensus on
site definition.
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