LINKPlanner shows a tolerance for the Predicted Receive Signal Strength which varies depending on the product and whether or not the link is Line of Sight (LOS).
In LOS conditions the default tolerance is due to the equipment performance rather than any variations in the prediction method. There are small variations in the equipment which account for production variations and variations across the full operating temperature range of the product. The equipment tolerances are defined separately for the transmitter and receiver.
When predicting the receive signal power we need to combine the tolerance of both the transmitter and the receiver and account for the fact that the transmitter may be at one end of its tolerance range and the receiver at the other. For example where we show a receive level tolerance of ± 5 dB, this is usually comprised of a ± 2 dB tolerance on the transmitter and a ± 3 dB tolerance on the reported receive level.
LINKPlanner is a global product and has to allow for installations at both extremes of the temperature range, which makes it difficult to reduce this tolerance. The majority of typical correctly aligned installs in mid-temperatures should have a tolerance of less than ± 2dB in LOS of conditions.
In non-LOS conditions then there is an additional variation due to the uncertainty of the obstruction loss. Where the obstruction is foliage then there will be fluctuations in the received signal level during normal operation, which can often be seen during install, depending on the weather conditions, how windy it is and whether it is wet or dry, etc.
Due to the resolution of the mapping data (typically 30m) it is also difficult to show the obstructions exactly and this leads to an uncertainty in the Excess Path Loss calculation. In LINKPlanner there is additional tolerance added to the equipment tolerance which is proportional to the amount of excess path loss on the link.