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Glossary
RPE-LTP Regular Pulse Excitation Long Term Prediction. A commonly
used technique for converting voice from analog to digital form.
This is the CODEC that is used by GSM, DCS1800 and
PCS1900 systems.
RSSI Received Signal Strength Indicator. Reception level.
SACCH There is a spare frame every 12 TCH frames and this is used for
the SACCH (Slow Associated Control Channel). On the down-
link, the SACCH is used to send slowly but regularly changing
control information to the mobile. The up-link carries
information about the received signal strength (RXLev) and
quality (RXQual)of the TCH and the adjacent cell BCH
measurement.
SDCCH The SDCCH (Stand-alone Dedicated Control Channel) is
sometimes configured on a BCH and sometimes on its own
physical channel. The SDCCH has a different multiframe
structure to the TCH. SDCCH bursts repeat less frequently than
one per frame. For this reason, more than 8 SDCCH can share a
physical channel. The data rate on a SDCCH is lower than on
the TCH. During the call set-up process, there can be a lot of
time between the mobile sending a RACH and getting service,
to the start of the conversation. During this period, no speech is
transmitted (though communication does take place). This
transitional time means less of the cells resource are used, the
SDCCH improves efficiency and provides a useful holding
channel for the mobile until, speech data needs to be
exchanged.
SIM The SIM (Subscriber ID Module) card plugs into every GSM
mobile and holds all the unique subscriber information. It also
stores dialing lists, network allowable usage etc.
SMSCB Short Message Service Cell Broadcast. This service is
analogous to the Teletext service offered on television. It
permits a number of unacknowledged general messages to be
broadcast to all mobiles in a particular region.
Speech Coder An electronic circuit that converts the audio signal into data and
minimizes the number of bits needed to represent the audio.
Trigger Delay The time delay between a valid trigger event and the digital
demodulation of the signal, or the delay between the trigger
event and the beginning of a measurement.