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User Manual
Airbridge cBTS3612 CDMA Base Station
daisy chains for BCPMs. The BRDM connects via the shorter daisy chain provided
to BCPM to form a standard daisy chain, which helps to improve the utilization ratio
of channel resource and facilitates the flexible configuration of channel capacity for
each sector carrier. BRDM exchanges O&M information with BCKM through the
backplane bus. The emergency serial port of BRDM is attached on the UART of the
backplane as a standby node.
3) BCPM
BCPM processes BTS baseband signals, both for the forward traffic and reverse
traffic. For forward traffic, it performs functions such as encoding (convolutional code,
TURBO code), interleaving, spectrum spreading, modulation and data multiplexing.
For reverse traffic, it performs functions such as demultiplexing, demodulation,
de-interleaving and decoding (convolutional code, TURBO code). Regarding the
user data flow, BCPM is between BRDM and BCIM.
4) BCIM
BCIM transfers data between BTS and BSC, including voices, data and O&M
commands. With the Inverse Multiplexing on ATM (IMA) technology, BCIM
multiplexes the BTS uplink data to IMA link set that is composed of multiple E1s,
and then transmits it to BSC via coaxial or optical fiber. Inversely, it can also
demultiplex the IMA link set signals from BSC into an ATM cell flow and transmit it to
BTS boards via the backplane bus.
5) CBKM
CBKM performs interconnection of high-speed data links between boards in the
baseband part and the interconnection of various management and control signals
of boards.
II. RF subsystem
BTS RF subsystem is composed of five parts: BTS Transceiver Module (BTRM),
BTS High Power Amplifier M odule (BHPA ), BTS Transceiver Backplane Module
(BTBM), Duplexer Unit and Receive LNA Distribution Unit (RLDU). Functions of all
parts are briefed as follows:
1) BTRM
BTRM consists of BTS Intermediate Frequency Unit (BIF U), and BTS Radio
up/down-conversion Unit (BRCU). Its functions are as follows:
BIF U: BIFU performs such functions as A/D conversion in the reverse receiving path
and D/A conversion in the forward transmitting path, digital frequency up/down
-conversion, received signal filtering, baseband molded signal filtering, Digit
Automatic Gain Control (DAGC), uplink & downlink RF Automatic Gain Control
2-3
System Description
2 Hardware Architecture
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