Loss), the attenuation caused by obstacles (Excess Path Loss), and a margin to allow for possible fading
of the radio signal (Fade Margin). The following calculation needs to be performed to judge whether a
particular link can be installed:
Free space path loss is a major determinant in received (Rx) signal level. Rx signal level, in turn, is a major
factor in the system operating margin (fade margin), which is calculated as follows:
System Operating Margin (fade margin) dB = Rx signal level (dB) – Rx sensitivity (dB)
Thus, the fade margin is the difference between the strength of the received signal and the strength that
the receiver requires for maintaining a reliable link.
Adaptive modulation
Adaptive modulation ensures that the highest throughput that can be achieved instantaneously will be
obtained, taking account of propagation and interference. When the link has been installed, web pages
provide information about the link loss currently measured by the equipment, both instantaneously and
averaged.
Data network planning
This section describes factors to be considered when planning ePMP data networks.
Ethernet interfaces
The ePMP Ethernet ports conform to the specifications listed in Table 130.
Table 130 Ethernet bridging specifications
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