Path Loss Considerations; Aggregate Ethernet Throughput Rate Versus Maximum Link Loss; Equation 1 - Path Loss - Motorola PTP 400 Series User Manual

6.1.3

Path Loss Considerations

The path loss is the amount of attenuation the radio signal undergoes between the two ends
of the link. The path loss is the sum of the attenuation of the path if there were no obstacles in
the way (Free Space Path Loss), the attenuation caused by obstacles (Excess Path Loss)
and a margin to allow for possible fading of the radio signal (Fade Margin).
Where
6.1.4

Aggregate Ethernet throughput rate versus maximum link loss

The equipment capability is given in Table 8 and Table 9. It gives the Ethernet throughput
rate versus link loss for the PTP 400 Series Bridge in both modes. Adaptive modulation will
ensure that the highest throughput that can be achieved instantaneously will be obtained
taking account of propagation and interference. The calculation of Equation 1 needs to be
performed to judge whether a particular link can be installed. When the link has been installed
web pages provide information about the link loss currently measured by the equipment both
instantaneously and averaged. The averaged value will require maximum seasonal fading to
be added and then the radio reliability of the link can be computed.
The full calculation is relatively complicated and thus Motorola has supplied a PTP Link
Estimator that calculates the radio propagation and reliability of NLOS links using the PTP
400 Series Bridge equipment.
+ +
L L L
free _ space excess fade
L Free Space Path Loss (dB)
free _ space
Excess Path Loss (dB)
L
excess
L Fade Margin Required (dB)
fade
Seasonal Fading (dB)
L
seasonal
L Equipment Capability (dB)
capability

Equation 1 - Path Loss

46
+ <
L L
seasonal capability