CAPACITY PLANNING USING BTS (DTRU)

Lab # 7Engr. Mehran Mamonai

DTRU

The Double-Transceiver Unit (DTRU) is placed in the double-transceiver subsystem of the BTS. One DTRU consists of two TRXs.

DTRU 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 DTRUThis 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 DTRUThis 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 DTRUThis 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 DTRUThis describes the size, working voltage, power consumption, and weight of the DTRU.

Functions of the DTRU

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

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.

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

Working Environment of the DTRU

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).

Functional structure of the DTRU

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: 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

Functional structure of the DTRU

Functional modes of the DTRU

RF Transmit Mode Transmit independency mode PBT mode Wideband combination mode Transmit diversity mode

Transmit Independency Mode

The two TRXs work independently without using the combination unit

PBT Mode

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

Wideband Combination Mode

The two transceivers are combined through a combiner before transmission.

Transmit Diversity Mode

One route of baseband signals are divided into two routes. Thus, the downlink receive level of the MS is improved

Functional modes of the DTRU

RF Receive Mode Receive Independency Mode Receive Diversity Mode 4-way Receive Diversity Mode

Receive Independency Mode

Each TRX of the DTRU uses the main and diversity ports of itself

Receive Diversity Mode

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

4-way Receive Diversity Mode

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

DTRU Panel

Specifications of 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

DAFU subrack

The DAFU subrack can be configured with the DDPU, DCOM

Functions of the DDPU

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

Working Principles of the DDPU

Functions of the DCOM

The DCOM combines two routes of TX signals from the DTRU, and then sends them to the DDPU.

Working Environment of the DCOM

Assignment

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)