FINAL REPORT - Stakeholders - Ofcom

6.5.2.3 Globe Wireless e-mail HF communication system
In addition to the Norwegian trials a large commercial global HF communications network
has been implemented by Globe communications. The Globe e-mail HF communication
system has been in operation for about 9 years and uses a network of 23 sites in different
countries around the world. Communications are fully automated and no radio operator
skills are required. Software clients similar to those used with Internet email are employed
and more than 4,000 ships, including those of all the major flags, use the system.
It would appear that the capability, availability and reliability of this system may make it an
ideal terrestrial wireless option for safety and reporting requirements such as those
demanded by IMO mandated requirements of security alerting and long-range AIS.
The system is much cheaper to operate than a satellite system while at the same time
offering similar capabilities. GlobeEmail is an automated system, both from shore to ship
and in the reverse direction. Every ship participating in the system is provided with
customised software and a dual mode modem. The user on the ship uses the simple email
client to send and receive messages, in a similar manner to POP3 E-mail. Another
part of the software controls the HF radio. It scans the radio, sampling every channel
used and identifies the six best frequencies, at any point in time. It also monitors the ‘outbox’
of the E-mail program and when a message is placed there, it automatically links
with one of Globe’s shore stations and transmits the message. Sophisticated, errorcorrecting,
transmission protocols have increased the reliability significantly and a
network of stations around the world, linked to a central control point, provides coverage
world-wide, including the polar-regions. This system and others like it were designed to
overcome the deficiencies of past marine communications systems and any file, text,
graphic or binary can be sent via radio. It is claimed that speed, reliability, and coverage
is better than Inmarsat Standard C satellite performance.
The combination of Digital Signal Processing and adaptive techniques produces the
lowest available underlying marine communications costs. This is because a terrestrial
system does not have to contribute to expensive space segment costs and does not have
to invest in uplink earth stations.
Standard HF radios and inexpensive computers can provide the enhanced adaptive
techniques required for this service.
Other developments have included technology that allows HF radio to transmit binary
files. Previously radio NBDP and SITOR was the most sophisticated protocol available to
ships. Telex has a very limited character set and is unable to transmit files such as word
processing documents, spreadsheets, or interact with on line services. A new technology,
named CLOVER, brings all of these features to HF radio. This new technology also
dramatically improves the throughput available on HF radio. Telex operates at 50 Baud
(bits per second). The GlobeEmail, using CLOVER moves data at a rate of 2400 bits per
second.
CLOVER is robust even under the poorest propagation conditions due to its use of a very
low base data rate that relies upon differential modulation between pulses. The CLOVER
signal fits perfectly within existing channel allocations because it consists of a time
sequence of amplitude-shaped pulses. Its data throughput is always the highest possible
since the CLOVER modem is capable of shifting among ten different modulation modes
using various combinations of frequency, phase-shift and amplitude modulation.
Some of the more important spectrum related and operational requirements of the system
are:
• The system should have the ability to simultaneously transmit and receive on a
single channel pair of frequencies.
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