Probabilistic Methods
This method is based on RSS and RSSI but uses the data from the offline survey ( Scene
Analysis ) in it’s advantage. The main idea is that it determinates the node based on the
RSS by using a predefined probability formula. Ex: if the RSS from the node in position
1 and 2 is equal and P(1) > P(2) then the system determinates that the position of the
node is 1.
In literature this method is commonly used in outdoor scenario because of the huge
problems with RSS in indoor environments.
Some interesting algorithms have been created and studied from empirical formulas and
specific environments but the drawback of these algorithms is they are applicable in good
conditions only in those cases, for our case we have to modify them to account for the
errors.
There are different ways of applying this method either in the network or the node, but
some need good computational power and can’t be done in real time. The accuracy for
this method is very high but it needs a lot of data and calibration from the offline survey.
Also while reading for this method I found RADAR a method developed by Microsoft to
keep track of there employs in the building and I attached it along the literature for this
summary.
Literature:
Vaidyanathan Ramadurai, Mihail L. Sichitiu; “Localization in Wireless Sensor
Networks:A Probabilistic Approach” {1}
Paramvir Bahl and Venkata N. Padmanabhan; “RADAR: An In-Building RF-based User
Location and Tracking System” {2}
Radu Stoleru , John A. Stankovic; “Probability Grid: A Location Estimation Scheme for
Wireless Sensor Networks” {3}