The basic goal of the probabilistic relation based positioning is to get both user signal strength relations and database fingerprint positions signal strength relations

The basic goal of the probabilistic relation based positioning is to get both user signal strength relations and database fingerprint positions signal strength relations, and calculate probability for every candidate position, after which the position with the highest probability is chosen. The position method assumes, that AP signal strength values are Gaussian distributed with a common variance.
The relation in the context of this document means the difference between the signal strengths in logarithmic decibel scale. As demonstrated in the previous example, relation of two signal strength values ¬83dBm and ¬81dBm is +2dBm. If we have two signal strengths X and Y that are Gaussian distributed, then the random variable in probabilistic relation based method is the difference between them: Z = X ¬- Y , that is also Gaussian distributed. Mean of the random variable Z is