Localization using RFID reader

Hello ,
I am trying to Localize the position of an Asset tag using Active RFID reader,
Search Results : RFID reader, RFID tag, RFID solutions - GAO RFID Inc., for more detail on the reader.
The RSSI i have obtained are not logical.
Any suggestions?
Regards,
Sara

What make you think, that the RSSI values give a reliable distance information? They are e.g. affected by antenna
directional characteristics (of both tag and receiver) and multipath receiption within the fresnel zone.