RSSI FingerPrinting and Localization in WSN

WSN(Wireless Sensor Network) is a network includes sensor nodes,gateways and communication between sensor nodes is radio.In a wireless sensor network,if you want to localize where a node is is so difficult because there are many sensor nodes wherefore Localization in WSN is a problem needs accurate solutions.
At present there are a lot of algorithms for how to localize for example classical algorithms (Triangulation,FingerPrinting...), recently algorithms(RFID...).In this post I will introduction FingerPrinting algorithms by using RSSI (so called RSSI Fingerprinting).
This algorithm is divided in 2 phases:

1. Creating Fingerprinting database(called offline phases): It means the RSS is measured at each predetermined location to create a database of RSS patterns.The database of RSS patterns is called a radio map.
   
2. Location estimation(called online phases):It means from received RSS will compare with the database of RSS patterns and use a positioning algorithm to estimate the location of the mobile station.

The advantage of this algorithm is that not require the mobile station to see at least three base station in order to determine the location.
The disadvantage of this algorithm is that it is very time-consuming to perform an exhaustive data collection.

PS:My english really is so bad...Thx for reading!