The rejection factor defines how the interfering signals produced by transmitters bellonging to any service will affect the desired signal depending on their frequency separation. It is defined using a mask formed by a set of pair of value (separation in frequency and attenuation).

The way in which a receiver is affected by interference depends on the service of the receiver itself as well as the service of the interfering transmitters.

In order to take interference from all types of sources into account, in all interference calculation, it is necessary to set an interservice rejection factor that determines the rejection factors and the co-channel protection relationships for each Txservice - Rxservice relationship that may arise during the calculation.

Co-channel protection ratio is the minimum difference that there must be between the desired signal and the interfering co-channel. This parameter is only used in the calculation of the usable field as described in the "Interference calculation" section.