ADC Telecommunications Inc. DVICS800-1 User Manual
ADCP-75-110
•
Issue B
•
March 2001
Page 16
©
©
2001, ADC Telecommunications, Inc.
2 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-buildling coverage solution using the
Digivance
ICS. System design and planning services are available from ADC if required. Refer to
section
6 of this manual for additional information.
2.1 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.
2.1.1 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 the DHU and BTS. The correct levels can be provided at the
BTS
and DHU using the Local Interface Unit (LIU). The LIU is an accessory item that
provides
adjustable gain or attenuation in both the RF forward and reverse path. The level of
the
RF output signal from the BTS will vary depending on the type of BTS. Therefore, it will
generally
be necessary to add some gain or some attenuation to the forward path (downlink)
signal
to provide the recommended composite maximum RF input signal level at the DHU
which
is–20 dBm. When the level of the RF input signal at the DHU is –20 dBm, the level of
the
RF output signal at the DRU will be +13 dBm which is the maximum allowed.
In
the reverse path, the input signal level required at the BTS will also vary depending on the
type
of 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
is –30 dBm. Therefore, it may be necessary to add some gain or attenuation to the
reverse
path signal in order to achieve the required RF input signal level at the BTS. A block
diagram
showing a typical local DHU to BTS interface is provided in Figure 8.
LOCAL
INTERFACE
UNIT
FORWARD
(DOWNLINK)
REVERSE
(UPLINK)
+13 dBm
(COMPOSITE
MAX)
-40 dBm
(COMPOSITE
MAX)
-20 dBm
(COMPOSITE
MAX)
-30 dBm
(COMPOSITE
MAX)
Fig 8B-A
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
Figure 8. Local BTS Interface Block Diagram