Indoor distance estimation for passive UHF RFID tag based on RSSI and RCS

We develop a new procedure to estimate the indoor distance for passive UHF RFID tag, the estimation concept relies on the relationship between radar cross section RCS of the maximum effective reading distance and any measured distance at 928 MHz multiplied by received signal strength indicator RSSI ratio. It gives a high accuracy in two stages. In the first stage, the percentage accuracy of the estimated distance is trained, and a percentage polynomial curve is created; this curve is used to increase the accuracy in the second stage which ranges from 90.3% to 100.0% with root mean square error RMSE 0.02.