User's Manual

ADCP-75-132 • Issue 2C • August 2006
Page 17
© 2006, ADC Telecommunications, Inc.
3 INSTALLATION PLANNING AND SYSTEM DESIGN
This section provides installation planning information and basic system design recommendations
for RF engineers that will be designing and installing an in-building coverage solution using the
Digivance ICS. System design and planning services are available from ADC if required. Refer to
Section 7 of this manual for additional information.
3.1 Base Station Interface Requirements
The DHU may be interfaced either locally or remotely with the BTS. As referenced in this
publication, the BTS could be either a microcell or a cell site base station. With a local
interface, a hard-wire connection is provided between the DHU and the BTS (microcell) using
coaxial cables. With a remote interface, an over-the-air connection is provided between the
DHU and the BTS (cell site base station) using a donor antenna.
3.1.1 Local BTS (Microcell) Interface
A local interface between the DHU and the BTS (microcell) over coax requires specific RF
input and output signal levels at both the DHU and BTS. The correct signal levels can
generally be provided by inserting attenuation in the forward and reverse signal paths.
In the forward path, the correct input level can be provided at the DHU using the High Power
Conditioning Panel (HPCP). The HPCP is an accessory item that is used to attenuate the
forward path RF signal. The HPCP provides attenuation adjustments in 1 dB increments over
a range of 40 to 70 dB. A block diagram of a typical local BTS interface is shown in Figure 8.
The maximum RF input signal level the DHU will accept is determined by the DHU overdrive
limiter. When the RF signal input to the DHU is set to 1 dB below the DHU overdrive level, the
RF signal output at the DRU will be at the specified maximum level (see Table 6). The level of the
RF signal output at the DRU is dependent on the modulation protocol and the number of carriers.
HIGH POWER
COND. PANEL
FORWARD
(DOWNLINK)
REVERSE
(UPLINK)
COMPOSITE MAX
PER TABLE 6
-40 dBm
(COMPOSITE
MAX)
COMPOSITE
MAX PER
ADJUSTMENT
PROCEDURE
-30 dBm
(COMPOSITE
MAX)
17792-C
DIGITAL
HOST
UNIT
OPTICAL LINK
OPTICAL LINK
DIGITAL
REMOTE
UNIT
DIRECTIONAL ANTENNA
TO/FROM HANDSETS
LOCAL BASE
TRANSCEIVER
STATION
(MICRO CELL)
T1 LINK
TO SWITCH
EXTERNAL
ATTENUATOR
(IF REQUIRED)
Figure 8. Local BTS Interface Block Diagram
In the reverse path, the input signal level required at the BTS can generally be provided using
an external attenuator or by adjusting the BTS. When the level of the reverse path (uplink)
signal at the DRU is at the recommended composite maximum of –40 dBm, the level of the
RF output signal from the DHU will be –30 dBm.