Various embodiments of the invention may use code division multiple access (CDMA) technology in communications from radio frequency identification (RFID) tags to RFID readers, so that multiple RFID tags may respond to the same RFID reader at the same time on the same frequency and still be reliably decoded by the RFID reader. In some embodiments, orthogonal CDMA PN sequences for the RFID tags to use in creating their responses may first be transmitted to those RFID tags, possibly using a non-CDMA technique.