.
Page
All Rights Reserved
Shyam Telecom Limited
33/43
Next Generation
Signal Enhancement
•
A
dequate separation is to be ensured from the power lines to
avoid damage to the equipment and humans.
•
A
ntenna with proper characteristics to maintain adequate isolation
to avoid oscillations.
N
ormally, isolation should be
15
d
B
more
than the gain set for the repeater. It should have good front to
back ratio.
•
T
he beam width for the
DONOR
antenna should be as small as
possible.
•
T
he
SERVER
antenna with proper gain required, is installed.
•
T
here should be adequate vertical
&
horizontal separation
between the
DONOR
&
SERVER
antennas to avoid
interference and noise.
S
eparation can be determined by the mathematical formulas:
V
ertical
S
eparation:
I
solation
(
d
B)
=
28
+
40
log
(D/
λ
in meters
)
H
orizontal
S
eparation:
I
solation
(
d
B)
=
22
+ 20
log
(D/
λ
in meters
)
–
(
Gain of donor
antenna
+
gain of server antenna
)
D
-
D
istance between donor
&
server antennas in meters
λ
–
W
ave length in meters
c) O
verlapping
C
overage
I
deally, the repeater system will be engineered with minimal overlapping
coverage between the donor base station and the repeater.
H
owever, the
mobile users will occasionally receive signals from both the donor and the
repeater at similar levels.
T
his situation is comparable to a mobile receiving
multiple signals at varying times due to multi-path propagation.
T
he repeater contributes a maximum signal delay of 5.5 microseconds in
one direction.
d) C
all
P
rocessing
T
he mobile communication system perceives calls handled by the repeater
as actually being handled by the donor site
(BTS);
the repeater is just an
extension of the base station’s coverage. Therefore, the donor handles call
initiation, power control messages, hand-over requests, etc., for mobiles in
the repeater area.
W
hen the base station assigns a channel to the mobile,
that channel is sent through the repeater and then re-radiated under the
same frequency.
S
ince the repeater is technically part of the base station,
no hand-over takes place when a mobile moves from the repeater’s
coverage area to that of the base station.
W
hen the mobile moves from the
