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Section 10: GSM
T
ieline
Page 81
T E C H N O L O G Y
Section 10. GSM
GSM networks deliver wireless high
quality and secure mobile voice and
data. Today's highly successful GSM
wireless technology has become the
world's leading and fastest growing
mobile standard, spanning over 190
countries.
Figure 22: Tieline GSM Module and Antenna
Cell phone networks provide a voice channel and a data channel. The
T
ieline
GSM
data facility connects over the data channel and is therefore relying on the Telco’s
commitment to wireless data integrity, bit rate allocation and link reliability.
VERY IMPORTANT WARNING:
GSM plug-in modules cannot be used in TLR300B
COMMANDER
G
3
rack unit
codecs. If you must connect using GSM with aTLR300B
COMMANDER
G
3
rack
unit codec, we suggest you use a GSM cell-phone attached to the RS232 port on the
rear panel of the codec. Alternatively, you could try a GSM phone or a 3G cell-phone
in GSM mode with a
T
ieline
USB module.
10.1. How does it work?
GSM uses a process called Circuit Switching. Circuit-switching is a method of
communicating where a communications path is established between two devices
through one or more switching nodes. The digital data is sent as a continuous
stream of bits, allowing the data to be heard from the receiving end whilst the
data is still being sent. This makes circuit switching an ideal method of sending
real time audio. This is different from GPRS which sends packets of information
which need to be reassembled before they can be heard and is therefore not
suitable for real time audio broadcast applications. Circuit Switched Data (CSD)
enables single channel data at 9,600bps.
10.2. HSCSD Information courtesy of GSMworld.com
HSCSD (High speed circuit switched data) is a real time delivery protocol
compared with GPRS which is a non-real-time packet based technology. HSCSD
allows users to send and receive data at speeds of 28.8kbit/sec and 43.2kbit/sec
by enabling up to 4 traffic channels of a GSM network.
HSCSD is only available in a few countries. Some of these are the UK, Germany,
Switzerland, Singapore and Canada. Go to www.gsmworld.com to see if HSCSD
is available in your region.