A radio frequency identification (RFID) tag and a method of monitoring Quality of Service (QoS) of a RFID tag

The RFID tag (200) comprising: a first communication module (201) to receive signals from a RFID reader (100) and including means for extracting energy from the received signals providing a supply voltage Vdd to the RFID tag (200); an energy storage module (203) to store said extracted energy from the received signals of the RFID reader (100); a second communication module (202) to communicate with an external device (300); a power output (204) to provide a power-supply voltage to the external device (300) using said stored energy; a control module (205) to perform a tracking of said power-supply voltage provided by said power output (204), wherein the first communication module (201) also transmits to the RFID reader (100) a quality indicator of an energy status of the RFID tag (200) based on the result of said tracking.