Huawei BTS3 Series, Hardware Description Manual

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3 Board
M900/M1800 BTS3X Series Base Transceiver Station
Hardware Description Manual
3-70 Huawei Technologies Proprietary Issue 01 (2006-11-18)
the TRX, the CDU, the PMU and the TES), it is possible to realize the O&M operation on the
entire system, centralize the downloading and saving of the software loaded to various units,
and support the connection to the MMI at a PC.
The flash memory of the OMU can store two different versions of the BTS software. One of
the two versions is under current use. The OMU can load one of the two versions to each
board according to the request of BSC as the current operation software. If the BTS software
is upgraded, the BSC can load the new software to the OMU for saving through O&M Link
(OML). The new software is used as the substitute of the previous version. At the same time,
the previous version is also backed up in the OMU in case of upgrading failure.
MCK
The MCK has an OCXO complying with the AAA standard and a phase-locked frequency
dividing circuit. The OCXO output standard 13 MHz system reference clock. According to
the system configuration, the MCK can work in free run mode or software phase-locking
mode. Through the frequency dividing of the reference clock, it can output the reference clock
(SREF) with the stability higher than 5
%
10
-8
ppm, and provides the frame clock (FCLK), 1/8
bit clock (OBCLK) and frame number (FN), etc.
The clock is the "calendar" and "pulse" of TDMA system. Therefore, its reliability is very
crucial. The clock source of a synchronous cell is provided by the MCK on TMU in the main
cabinet. The MCKs of two boards are the hot backup of each other. When the main board is
faulty, the switchover will be implemented to activate the standard board, and report it to
OMU.
The frequency, period, and duty ratio of various system clocks are listed as follows:
!
13 M: 13 MHz, duty ratio: 50%
!
SREF: 13 MHz/4 = 3.25 MHz, period: 307.7 ns, duty ratio: 50%
!
OBCLK: 13 MHz/6 = 2.167 MHz, period: 461.5 ns, duty ratio: 50%
!
FCLK: 13 MHz/6/10000 = 216.7 Hz, period 4.615 ms, duty ratio: 50%
!
The FN increases by 1 after each frame clock period
Figure 3-46 shows the time sequence of clock signals.
Figure 3-46
Time sequence of clock signals
13MHz
OBCLK
FCLK
D31 D30
FN
EAC
This module collects external alarm signals and reports the signals to the OMU.
3.21.3 Panel
Figure 3-47 shows the TMU panel.