Technical data

Chapter 12 371
GSM and EDGE Analyzer
GSM and EDGE Modulation and Band Information
GSM and EDGE Analyzer
GSM and EDGE Modulation and Band Information
The standard includes multiple traffic channels, a control channel, and a cell
broadcast channel. Although the GSM specification defines a channel spacing of
200 kHz, it is worth noting that service providers often space their channels 400 kHz
apart.
GSM 450, GSM 480, GSM 900, GSM 850, DCS 1800, and PCS 1900 are
GSM-defined frequency bands. The term GSM 900 is used for any GSM system
operating in the 900 MHz band, which includes P-GSM, E-GSM, and R-GSM.
Primary (or standard) GSM 900 band (P-GSM) is the original GSM band. Extended
GSM 900 band (E-GSM) includes all the P-GSM band plus an additional 50
channels. Railway GSM 900 band (R-GSM) includes all the E-GSM band plus
additional channels.
DCS 1800 is an adaptation of GSM 900, created to allow for smaller cell sizes for
higher system capacity. PCS 1900 is intended to be identical to DCS 1800 except for
frequency allocation and power levels. The term GSM 1800 is sometimes used for
DCS 1800, and the term GSM 1900 is sometimes used for PCS 1900. For specifics
on the bands, refer to “GSM and EDGE Modulation and Band Data” table below.
The framing structure for GSM measurements is based on a hierarchical system
consisting of timeslots, TDMA frames, multiframes, superframes, and hyperframes.
One timeslot consists of 156.25 (157) symbol periods including tail, training
sequence, encryption, guard time, and data bits. Eight of these timeslots make up
one TDMA frame. Either 26 or 51 TDMA frames make up one multiframe. Frames
13 and 26 in the 26 frame multiframe are dedicated to control channel signaling.
EDGE (Enhanced Data for Global Evolution) is an enhanced version of GSM that
uses 8PSK (8-Phase Shift Keying) as opposed to the GMSK (Gaussian Minimum
Shift Keying) of GSM. EDGE can therefore transmit three times as many bits per
symbol as GSM while using the same framing structure.