Service Manual

GSM-204-323
Compact transceiver unit (CTU)
31st Oct 01
Technical Description: Horizon macro outdoor
68P02902W02-A
CONTROLLED INTRODUCTION
Tech. 5–19
CTU
uplink/downlink
Downlink traffic data flow
Downlink TRAU data is received by the TDM function from the MCUF. This data
is then routed to the CCCP function, where it is encoded (cyclic, block, and
convolutional), interleaved, and encrypted to GSM recommendations.
Signalling messages are also received from the RSS processor and encoded.
These traffic and control messages are built into air interface frames and then
routed back to the MCUF via the TDM function for baseband hopping. The
CCCP calculates a BBH routeing word, which informs the MCUF as to which
fibre link it would like to be the source of its post-hopped data. The post-hopped
data is then once again sent back down to the appropriate CTU where it is
received by the TDM function and passed to the EQCP function. The EQCP
inserts training sequence and guard bits to the data bits and forwards the data
on to the modulator for transmission. The EQCP also programs the CTU for the
correct RF channel and transmit power level for this transmitted burst.
Uplink traffic data flow
Baseband uplink traffic and control data messages are received by the CTU
interface function and sent to the EQCP where they are equalized. The EQCP
also calculates timing advance and RXLEV information, which is forwarded to
the RSS process. The recovered data bits are forwarded into the CCCP
process, where it is de-interleaved, decoded, and decrypted into TRAU frames.
Control messages are passed to the RSS function, while TRAU frames are sent
to the MCUF via the TDM interface.