User's Manual

WaveIP Ltd. GigAccess™ OFDM 5.8
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5
5
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A
A
p
p
p
p
e
e
n
n
d
d
i
i
x
x
B
B
–
–
R
R
F
F
L
L
i
i
n
n
k
k
B
B
u
u
d
d
g
g
e
e
t
t
C
C
a
a
l
l
c
c
u
u
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a
a
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n
n
Proper RF link planning ensures that the AU/SU receives sufficient signal power to
maintain the desired Bit Error Rate (BER). The following section gives a brief
description of the basic RF terms and describes the calculation of the maximum safe
distance versus the antenna gain.
A typical radio system is given hereunder:
AU
(Transmitter)
SU
(Receiver)
Gt
Gr
Pt Pr
Ct
Cr
Figure 5-1: Radio Link – General description
The following variables are used to calculate the link budget:
P
t
- Transmitted Power in dBm.
C
t
– Transmitter Cable Attenuation in dB.
G
t
- Transmitting antenna Gain in dBi.
EIRP – Effective Isotropic Radiated Power in dBm. This is the power radiating from
the antenna, taking into account the output power from the transmitter, connector
losses, cable losses and antenna gain.
PL - Path Loss in dB. This is the signal loss as it travels through the air.
G
r
- Receiving antenna Gain in dBi.
C
r
– Receiver cable attenuation in dB.
P
r
– Receiving Power Level at Receiver in dBm.
S
r
– Receiver Sensitivity in dBm (The minimum RF signal power level required at the
input of the receiver for certain performance: E^-5 BER).
F.M. – Fade margin in dB. The fade margin is the amount by which the system gain
plus total gain exceeds the path loss or in other words this is the number of dB
that the received signal strength exceeds the minimum receiver sensitivity. Any
wireless system requires some level of fade margin to compensate for RF path
fading due to weather conditions or multi-path interference. (The transmitted
signal arrives at the receiver from different directions, with different path length,
attenuation and delays. The summed signal at the receiver may result an
attenuated signal). GigAccess™ recommended fade margin at 5.8 GHz is
minimum of 6-10 dB.