What is HSCSD?
HSCSD
[High Speed Circuit Switched Data] falls under the general category of 2.5G
technologies and it provides high speed data for GSM based networks.
One
of HSCSD’s greatest advantages over GPRS, for example, is that it builds on
existing technology rather than requiring major upgrades to network
infrastructure. With HSCSD, all the operator is really doing is combining
(aggregating) a number of separate user sessions (or slots). It is technically
feasible to combine up to four slots but most users will configure their
handsets set to three slots receiving data and just one slot sending data back
to the network.
The
first group of operators to launch commercial HSCSD services back in 1999
included Europolitan of Sweden, E Plus of Germany, One in Austria, Telenor in
Norway, Sonera in Finland, M1 in Singapore and EuroTel in the Czech Republic.
They did so, however, using Nokia’s Card Phone 2.0 which works in portable
computers running Microsoft Windows software and possessing a suitable PCMCIA
communications port. For some time after HSCSD was initially launched,
therefore, there were no HSCSD compatible handsets. The situation has
subsequently improved with the launch of the Nokia 6210, the Siemens S40 (which
is shipping in North America) and the Ericsson 520 which offers both GPRS and
HSCSD. There is also the Orange Videophone from Orange UK which uses HSCSD.
In terms of raw data
throughput, the actual top speed for HSCSD depends on whether or not the
operator in question has upgraded the network’s support for simple circuit
switch data. By default, most GSM networks only offer users a data session
running at 9.6 Kbit/s but this capability can be raised to 14.4 Kbit/s per
session. This can lead to some confusion. Some operators are aggregating two
14.4 Kbit/s slots to provide 28.8 Kbit/s to the consumer while others are
aggregating three 9.6 Kbit/s slots to achieve the same result. For example, in
some networks subscribers are presently offered three times slots, each capable
of 9.6 Kbit/s, giving a top speed of 28.8 Kbit/s. However, it will soon be
possible to reach 43.2 Kbit/s (via three times 14.4 Kbit/s slots). Whichever
approach is adopted, HSCSD is currently still faster than GPRS that struggles to
provide users with higher than 20 Kbit/s connections.
