Understanding PMP 450m EIRP limits

The PMP 450m product can now use different EIRP values in different modes depending upon the regulatory limit. This only affects the EIRP limits at the AP and does not change anything at the SM, so only affects the downlink to the SM.

The original EIRP limit from previous versions (42 dBm for 5 GHz and 47 dBm for 3.5/3.6 GHz) is now known as the Sector limit. This is the EIRP used in broadcast mode and is the power used to report the receive level on the SM, so the reported SM receive level doesn’t change if the EIRP limit on the AP is increased above this level.

In MU-MIMO mode when the AP is communicating to multiple SMs in the 5 GHz band the transmit EIRP limit can increase to 44 dBm (in the 3 GHz bands it is the same as the sector limit).

When in sector mode or if the SM has sounding (i.e. reporting a spatial frequency) but is not grouping with any other SMs then the PMP 450m can now use beamforming to that individual SM increasing the EIRP to the beamforming limit, which is dependent on band and modulation mode.

The increased EIRP is reported in LINKPlanner as an improved fade margin in the Performance Details tab on the Subscriber Module and can translate into a higher Max Usable Mode.

In LINKPlanner the EIRP limit and maximum configurable value is now the minimum of the beamforming limit and the regulatory limit.


On the Subscriber Module there is new hover help information on the Predicated Receive Power in the Performance to SM section.


In the Performance Details there is new hover help information over the fade margin for each mode in the Performance to Subscriber Modules section, to help guide you on which value is being used and will change depending on the Operating mode configured and whether or not the SM is capable of grouping.

There is the possibility that the fade margin on the SM in lowest mode may look good enough to meet the required Availability requirements from the beamforming power, but in reality the Predicted Receive Power is too low to receive the beacons on the broadcast channel. In this case the Max Usable Mode will be shown as N/A as the link cannot be established.

Where there is the option to run the PMP 450m above the sector EIRP limit then a PMP 450m will now have enhanced performance in the downlink as well as the uplink even without enabling Mu-MIMO compared with a PMP 450i equivalent as the beamforming gain is applied in both directions. However, for users who have been used to switching between Sector and Mu-MIMO mode to compare before and after an upgrade this may appear to reduce the improvement as the Sector performance has improved.