User Manual

Architecture
Nortel Networks Confidential
3–44
PE/DCL/DD/0063
411–9001–063
Standard 12.07/EN September 2000
GSM/BSS V12
power control
call clearing
inter–cell handover
intra–cell handover
The BTS cyclically sends to the BSC the interferences measures done on the
inactive channels.
BB–FILT ASIC
The BB_FILT ASIC constitutes the interface between the signal processing unit
(SPU) of the DRX and the radio RX module on the one hand, and the enciphering
ASIC on the other hand. It carries out the band–pass filtering of the digital samples
output by the radio RX module, and generates the FH bus.
A single BB_FILT ASIC processes all eight TSs of the radio frame.
The functions provided by this ASIC include:
GSM time reception interface providing the synchronization of the DSPs on the
radio frame
on transmission:
• recording of the TX parameters and of the ciphering key, supplied by the DSP
EGAL
• transfer of the ciphering key to the CHIF ASIC
• reading of the ciphering template from CHIF ASIC
• ciphering of the parameters and transmission on the FH bus
on reception:
• recording of the RX parameters and of the ciphering key, supplied by the DSP
EGAL
• programming of RX hopping synthesizers
• generation of channel and sampling frequency selection signals for the analog
to digital converter
• base–band filtering of the digital samples delivered by the a dc converter
• selection of the best gain for each channel (normal and diversity)
• transfer of these selected filtered samples to the DSP EGAL
• transfer of the deciphering key to the CHIF ASIC
• reading of the deciphering template from CHIF ASIC, and transfer of the
template to the DSP EGAL
3.4.1.3 BDT unit
The BDT (time base) unit regenerates GSM TIME signals. The GSM time is
distributed to the BDT unit of each DRX by means of the GSM TIME channel of
the private PCM, every 60 ms.