Lab # 7
Engr. Mehran Mamonai
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The Double-Transceiver Unit (DTRU) is placed
in the double-transceiver subsystem of the BTS.
One DTRU consists of two TRXs.
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Functions of the DTRU
This descries the functions of the DTRU. The DTRU functionally consists
of the baseband processing part, RF transmitting part, and RF receiving
part.
Working Environment of the DTRU
This describes the working environment of the DTRU. The DTRUs are
inserted into the slots of the backplane in the DTRU subrack.
Working Principles of the DTRU
This describes the working principles of the DTRU. The DTRU consists of
the DTRU Baseband and RF Unit (DBRU), DTRU Power Amplifier Unit
(DPAU), and DTRU Power Supply Unit (DTPS).
LEDs and Ports on the DTRU
This describes the LEDs and ports on the DTRU panel. There are two
types of DTRU: type A and type B. The four LEDs on the DTRU panel
indicate the operating status of the DTRU and other functional
subsystems. DTRU (type A) has 10 ports and DTRU (type B) has 8 ports.
These ports exchanges signals with the RF front-end subsystem.
Specifications of the DTRU
This describes the size, working voltage, power consumption, and weight
of the DTRU.
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The DTRU functionally consists of the
baseband processing part, RF transmitting part,
and RF receiving part.
Baseband Processing Part
RF Transmitting Part
RF Receiving Part
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This describes the working environment of the DTRU.
The DTRUs are inserted into the slots of the backplane
in the DTRU subrack.
Figure 1 shows the working environment of the DTRU.
Figure 1 Working Environment of the DTRU
The working environment of the DTRU is as follows:
Receiving clock signals, control signals, and data
signals from the DTRB
Modulates the baseband signals into RF signals, and
then transmits the RF signals to the DAFU subrack
through RF signal cables
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The DTRU consists of the
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DTRU Baseband and RF Unit (DBRU),
DTRU Power Amplifier Unit (DPAU),
and DTRU Power Supply Unit (DTPS).
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The DBRU is the main functional module of the DTRU. It provides
modulation/demodulation, data processing, and
combining/dividing between the baseband signals and RF
signals.
The DTPS is the power supply board of the DTRU. The DTPS
converts the –48 V DC power into +28 V DC power for the DPAU.
The DTPS also supplies three routes of power required by the
TRX: 8 V, 4 V, and 3.3 V.
The DPAU performs the following functions:
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Amplifies the signals transmitted from the DBRU to the required power
level
Couples the output power for a loopback test and the power detection
Provides the detected temperature of the power amplifier
Provides wideband combination and PBT functions
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RF Transmit Mode
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Transmit independency mode
PBT mode
Wideband combination mode
Transmit diversity mode
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The two TRXs work independently without
using the combination unit
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One TRX in the DTRU is used.
One route of signals goes through modulation and DA
conversion.
As these two routes of signals are aligned in phase, the
output power is amplified after combination
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The two transceivers are combined through a
combiner before transmission.
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One route of baseband signals are divided into
two routes. Thus, the downlink receive level of
the MS is improved
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RF Receive Mode
Receive Independency Mode
Receive Diversity Mode
4-way Receive Diversity Mode
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Each TRX of the DTRU uses the main and
diversity ports of itself
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Each main (diversity) signal is divided into two routes
through a divider, and then sent to the main/diversity
port of the two TRXs. Note only two channels of RF
signals are routed into the DTRU through the RF cables
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Four routes of signals are sent to one TRX.
The 4-way receive diversity helps achieve more uplink gain than
the main receive diversity does.
Note in the 4-way receive diversity mode, only one TRX can be
used in the DTRU
Table 1 Specifications for the DTRU (type A)
Item
Specifications
Size
Size of the front panel (length x width):
389.2 mm x 68.1 mm
Working voltage
–48 V power input
Power consumption (heat
consumption)
Maximum power consumption with –
48 V DC input: 450 W
Maximum power consumption with
+27 V DC input: 390 W
Weight
9.2 kg
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The DAFU subrack can be configured with the
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DDPU,
DCOM
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This describes the functions of the DDPU.
The DDPU performs the following functions:
Provides lightning protection through the ANT
port
Detect VSWR alarms in the antenna system
Control the gains for the receive low noise
amplifier
Transmits multiple routes of RF signals from the
transmitter to the antenna
Receives signals from the antenna, amplifies and
quarters these signals, and then transmits them to
the receiver of the DTRU
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The DCOM combines two routes of TX signals
from the DTRU, and then sends them to the
DDPU.
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A site is to be configure which serves (a) 92 users,
who are present is parliament house. You have to
make three sectors. Tell by sketching, how many
DTRU cards, DCOM cards and Antenna can be
used. Also show connections
(b) 192 users
(c) 144 users
Urban (a/b/c)
Rural (a/b/c)