Service Manual

GSM-204-323
Compact transceiver unit (CTU)
31st Oct 01
Tech. 5–18
Technical Description: Horizon macro outdoor
CONTROLLED INTRODUCTION
68P02902W02-A
CCCP processor
The CCCP processor handles all the GSM specified layer 1 channel encoding
and decoding functions for speech and control data associated with the air
interface. In addition, it manages the routeing of TRAU frames and baseband
hopping (BBH) data, via the TDM interface, to and from the MCUF. The CCCP
functions include:
 Uplink channel decoding.
 Downlink channel encoding.
 GSM specified encryption algorithms.
 Baseband frequency hopping (not supported in GSM850 or PCS1900
BTS variants).
 TRAU frame collection and synchronization.
 Alarms management.
The CCCP communicates with the rest of the digital control functions via the
common PCI bus interface. A dual port RAM (DPR) is also used in the downlink
direction for communications from RSS. In addition to the TDM function, a serial
link is provided to support uplink and downlink TRAU data.
CTU interface function
The CTU interface function provides the air interface timing and radio control
circuitry required for Rx (uplink) and Tx (downlink) control functions. A common
PCI bus allows all the processing elements, including the RSS processor,
EQCP, and CCCP, to communicate with the various CTU functions. The CTU
interface includes:
 Master GSM air interface timing function.
 Independent Rx gain control interface for each diversity receiver branch.
 Baseband Rx data interface for each diversity receiver branch.
 Receiver front end and remote tune combiner control.
 Tx data interface, including GMSK modulator which provides baseband
data to the transmitter.
 Tx and power amplifier power control interface.
 Rx and Tx frequency synthesizer control, which supports RF frequency
hopping.
 CTU and cabinet alarm data collection.
 Alarms sampling and multiplexing.