Interference control method for RFID systems

A method for managing interrogation activities in a radio frequency identification (RFID) system having an RF reader unit and a plurality of RF tag devices, said method comprising the steps of:

• determining that an interrogation operation needs to be performed in the RFID system, said interrogation operation requiring the transmission of an interrogation signal from the RF reader unit to the plurality of RF tag devices;
• checking a spectral environment about the reader unit to determine whether an RF signal meeting a predetermined criterion exists within an operative frequency range of the RFID system;
• when an RF signal meeting the predetermined criterion does not exist within the operative frequency range of the RFID system, immediately transmitting said interrogation signal;
• when an RF signal meeting the predetermined criterion does exist within the operative frequency range of the RFID system, delaying transmission of the interrogation signal for a quasi-random delay period;
• and
• when transmission of the interrogation signal has been delayed a predetermined number of times, transmitting said interrogation signal regardless of whether an RF signal meeting the predetermined criterion does exist within the operating frequency range of the RFID system.

A method for use within a radio frequency identification (RFID) system having an RF reader unit and a plurality of RF tag devices, said method comprising the steps of:

• determining that an interrogation operation needs to be performed in the RFID system, said interrogation operation requiring the transmission of an interrogation signal from the RF reader unit to the plurality of RF tag devices;
• measuring a magnitude of radio frequency (RF) energy in a region surrounding the RF reader unit;
• comparing said magnitude of said RF energy to a predetermined threshold value;
• and
• transmitting said interrogation signal from said RF reader unit to said plurality of RF tag devices when said magnitude of said RF energy is less than said predetermined threshold value.