\subsection{\docWIFI}

	the smartphone's \docWIFI{} component provides an absolute location estimation $(x,y,z)^T$ by
	measuring the signal-strengths of nearby transmitters (\docAP{}) and comparing them with the signal-strengths
	that should be measurable. The latter are determined using a signal-strength prediction model.
	Thus, no fingerprinting is required. Solely the positions of the \docAP{}s must be known beforehand.%
	%
	Prediction uses the wall-attenuation-factor model \cite{ebner-15}
	which needs just three parameters: 
	the senders transmission power, the attenuation based on the distance from the sender, and the attenuation by floors/ceilings.
	To reduce the setup-time, the same values can be used for all transmitters at the expense of a worse location estimation / higher
	uncertainties.
	
\subsection{\docIBeacon{}s}

	If the building is equipped with \docIBeacon{}s, those may additionally be used as absolute location source.
	Like \docWIFI{}, measurements are compared with a model prediction based on the known transmitter position.
	The transmission power of the \docIBeacon{} is transmitted by the beacon itself and does not need any estimation beforehand.