Factory Line - Wireless LAN
1-6
PHOENIX CONTACT
7190_en_02
1.2.4.1
Example calculation for a transceiver system
All attenuations and all gains along a transceiver path must be taken into account when
calculating the radio path. The transmission properties for the relevant frequency range
must be known for all components.
For example, for a path in the 2.4 GHz ISM band, all values are added together (gains with
positive sign, attenuations with negative sign):
The receiver reserve should be greater than 10 dB. If the connection deteriorates, WLAN
switches to a more rugged transmission mode. This also changes the receiver sensitivity.
The values that can be achieved are listed in the technical data under "Receiver sensitivity".
1.2.4.2
Notes on receiver reserve and transmission quality
The following table lists guide values for transmission quality (at maximum transmission
speed) depending on the receiver reserve. The values are taken from experience and do
not take fall-back data rates into account; the real radio path may demonstrate different
behavior.
Transmission power
P = 15 dBm
+15.0
dBm
Transmitter cable
3 m cable
1 adapter
-2.9
-0.3
dB
dB
Transmitting antenna
Panel antenna
+8.0
dBi
Free space attenuation
Optimum line of sight 500 m
-94
dB
Receiving antenna
Panel antenna
+8.0
dBi
Receive cable
3 m cable
1 adapter
-2.9
-0.3
dB
dB
Receiver sensitivity
-87 dBm (must be viewed as positive)
+87
dBm
Final total
Receiver reserve
+17.6
dB
Table 1-3
Receiver reserve and transmission quality
Receiver reserve
Transmission quality
> 30 dB
Very high transmission quality
25 dB to 30 dB
High quality
20 dB to 25 dB
Satisfactory quality
15 dB to 20 dB
Sufficient quality, some packets will probably be lost
10 dB to 15 dB
Poor quality with clear loss of packets, communication may
be aborted at any time
< 10 dB
No communication, however may disturb other systems
