Motorola PTP 400 Series Manual De Usuario

 

 

46

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  

_

 

Free Space Path Loss (dB) 

 

Excess Path Loss (dB) 

 

Fade Margin Required (dB) 

 

Seasonal Fading (dB) 

 

Equipment Capability (dB) 

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.