User's Manual
ADCP-75-110 • Issue 2B • July 2001
Page 17
©
2001,
ADC
Telecommunications,
Inc.
The
LIU
is
rack
or
wall
mountable
and
is
powered
by
120–240
Vac
(50–60
Hz)
power.
Refer
to
the
Digivance
Local
Interface
Unit
User
Manual
(ADCP-75-113)
for
a
complete
description
of
the
LIU.
2.1.2 Remote BTS (Cell Site Base Station) Interface
A
remote
interface
between
the
DHU
and
the
BTS
(cell
site
base
station)
via
a
donor
antenna
requires
specific
RF
input
and
output
signal
levels
at
the
DHU
and
antenna.
The
correct
levels
at
the
DHU
and
antenna
can
be
provided
using
the
Remote
Interface
Unit
(RIU).
The
RIU
is
an
accessory
item
that
provides
adjustable
gain
or
attenuation
in
both
the
RF
forward
and
reverse
paths.
The
RIU
connects
to
a
directional
antenna
through
a
duplexer
which
provides
separate
forward
and
reverse
path
connections
for
the
DHU.
In
the
forward
path
(downlink),
the
RIU
provides
the
DHU
with
the
recommended
composite
maximum
RF
input
signal
level
of
–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
is
+13
dBm
which
is
the
maximum
allowed.
In
the
reverse
path,
the
required
RF
output
signal
level
to
the
donor
antenna
will
vary
depending
on
the
distance
from
the
BTS.
When
the
level
of
the
reverse
path
(uplink)
signal
at
the
DRU
is
at
the
recommended
composite
maximum
level
of
–40
dBm,
the
level
of
the
RF
output
signal
from
the
DHU
is
–30
dBm.
Therefore,
it
may
be
necessary
to
add
gain
or
attenuation
to
the
reverse
path
signal
in
order
to
achieve
the
required
output
signal
level
at
the
RIU
antenna
port.
A
block
diagram
showing
a
typical
remote
DHU
to
BTS
interface
is
provided
in
Figure
9.
The
RIU
is
rack
or
wall
mountable
and
is
powered
by
120–240
Vac
(50–60
Hz)
power.
Refer
to
the
Digivance
Remote
Interface
Unit
User
Manual
(ADCP-75-114)
for
a
complete
description
of
the
RIU.
DIRECTIONAL
ANTENNA TO/FROM
CELL SITE BTS
16425-A
REMOTE
INTERFACE
UNIT
FORWARD
(DOWNLINK)
REVERSE
(UPLINK)
+13 dBm
(COMPOSITE
MAX)
-40 dBm
(COMPOSITE
MAX)-20 dBm
(COMPOSITE
MAX)
-30 dBm
(COMPOSITE
MAX)
DIGITAL
HOST
UNIT
OPTICAL LINK
OPTICAL LINK
DIGITAL
REMOTE
UNIT
DIRECTIONAL ANTENNA
TO/FROM HANDSETS
Figure 9. Remote BTS Interface Block Diagram