Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
50(78)
14 Burst Timing (Power Time Template)
14.1 What is burst timing
The GSM system uses TDMA (Time Division Multiple Access).
The radio spectrum is divided into both frequency band and time slots.
The frequency band for EGSM 900 is divided in 174 frequencies (per direction) and the
frequency band for GSM 1800 is divided in 374 frequencies (per direction). Both of the
frequency bands has got eight time slots (channels) per frequency.
All information (speech and system information) are encoded and transmitted as a burst in a
time slot. Since several channels are sharing the same frequency is it vital for every burst to
start and end at the correct time.
The GSM specification describes the amplitude/time relation for the burst. Fig. 14.1 below
shows the amplitude limits for Power level 5 – 15, EGSM 900 and 0 – 15, GSM 1800, during
one burst.
Fig. 14.1
Burst timing is a part of the measurement in the Go/ No Go- test.
You can get a good look of the burst by checking the amplitude of the burst at some time
spots of the raise and fall slope of the burst Fig. 14. 1.
This let you know if the burst is within the limit.
Table 14.1 and Table 14.2 below show the limits of the timing for all power levels in EGSM
900 and GSM 1800.