Service Manual

GSM-204-323
CTU frequency hopping
31st Oct 01
Tech. 5–20
Technical Description: Horizon macro outdoor
CONTROLLED INTRODUCTION
68P02902W02-A
CTU frequency hopping
Overview of
CTU frequency
hopping
The CTU supports two types of frequency hopping, Synthesizer Frequency
Hopping (SFH) and BaseBand frequency Hopping (BBH). This section provides
an explanation of both types.
In both cases, the MS switches channels after every transmit/receive (Tx/Rx)
burst pair. The difference between SFH and BBH is in the method by which
channel switching is achieved at the BTS.
Synthesizer
frequency
hopping (SFH)
SFH uses the frequency agility of the CTU to change Tx/Rx frequency on any
timeslot (TS), without affecting other timeslots.
Only wideband (CBF/Hybrid) combining can be used with SFH.
With SFH, each TS is allocated a number of frequencies (max 64) over which to
perform the hopping. When determining the hardware requirement for CTUs
using SFH, the following rules apply:
 A minimum of two CTUs are required per cell due to BCCH requirements.
Timeslot 0 of CTU 0 is used for the BCCH carrier as shown in Figure 5-10.
CTU 0 cannot use SFH. Only CTU 1 and additional CTUs can use SFH.
 Hopping through the BCCH carrier (using the BCCH carrier frequency as
one of the SFH frequencies) is permitted except for timeslot 0. However,
the corresponding timeslot for the BCCH CTU will be switched off for this
period.
Figure 5-10 shows the minimum SFH requirement.
Figure 5-10 Minimum SFH requirement