RFID systems with session-dependent replies
RFID systems may be configured to use session-dependent replies. When an RFID tag is involved in a certain inventorying session, the tag may respond to inventorying commands with a reply that is at least partly generated based on the session. For example, the tag may generate a reply with a string that has parity based on the session or includes an identifier for the session. The string may be a random number, a tag identifier or item identifier, or any other suitable data sent from the tag.
1. A method for a Radio Frequency Identification (RFID) integrated circuit (IC) coupled to an antenna to operate in one of two inventorying sessions, the method comprising:
receiving an inventorying command, the inventorying command specifying one of the two inventorying sessions;
if the specified session is a first session, then selecting an odd parity;
if the specified session is a second session, then selecting an even parity;
generating a reply to the inventorying command indicating the specified session used by the RFID IC by:
generating a string for inclusion in the reply; and
adjusting a parity of the string to correspond to the selected parity; and
sending the reply with the parity-adjusted string indicating the specified session.
2. The method of claim 1 , wherein the string is one of a random number, a pseudorandom number, an algorithmically generated value, a cryptographic value, and a content of an IC memory.
3. The method of claim 1 , wherein adjusting the parity of the string comprises adjusting at least one of a parity bit, a checksum, a cyclic-redundancy-check, an error-detection code, and an error-correction code in the reply.
4. The method of claim 1 , wherein adjusting the parity of the string comprises at least one of:
adding at least one bit to the string such that the parity of the string corresponds to the selected parity; and
adjusting at least one bit of the generated string such that the parity of the string corresponds to the selected parity.
5. The method of claim 1 , further comprising:
receiving an encoding-switch command instructing the IC to begin generating non-parity-adjusted strings;
in response to receiving the encoding-switch command:
generating a string for inclusion in a reply to a subsequent inventorying command; and
sending the reply with the string without adjusting a parity of the string to correspond to the selected parity.
6. A method for a Radio Frequency Identification (RFID) integrated circuit (IC) coupled to an antenna to operate in one of a plurality of inventorying sessions, the method comprising:
receiving an inventorying command, the inventorying command specifying one of the two inventorying sessions;
selecting an encoding scheme based on the specified session;
generating a reply to the inventorying command indicating the specified session used by the RFID IC by:
generating a string for inclusion in the reply; and
adjusting the string according to the selected encoding scheme; and
sending the reply with the encoding-adjusted string indicating the specified session.
7. The method of claim 6 , wherein the string is one of a random number, a pseudorandom number, an algorithmically-generated value, a cryptographic value, and a content of an IC memory.
8. The method of claim 6 , wherein the encoding scheme is one of a parity encoding scheme, a checksum encoding scheme, a cyclic-redundancy-check encoding scheme, an error-detection encoding scheme, and an error-correction encoding scheme.
9. The method of claim 6 , wherein the encoding scheme comprises including a session indicator in the encoding-adjusted string.
10. The method of claim 6 , wherein selecting the encoding scheme comprises:
selecting a first encoding scheme if the specified session is one of a first session and a third session; and
selecting a second encoding scheme if the specified session is one of a second session and a fourth session.
11. The method of claim 10 , wherein the first encoding scheme has an odd parity and the second encoding scheme has an even parity.
12. The method of claim 6 , wherein adjusting the string according to the selected encoding scheme comprises at least one of:
adding at least one bit to the string based on the selected encoding scheme; and
adjusting at least one bit of the generated string based on the selected encoding scheme.
13. The method of claim 6 , further comprising:
receiving an encoding-switch command instructing the IC to begin generating non-encoding-adjusted strings;
in response to receiving the encoding-switch command:
generating a string for inclusion in a reply to a subsequent inventorying command; and
sending the reply with the string without adjusting the string according to the selected encoding scheme.
14. A Radio Frequency Identification (RFID) integrated circuit (IC) configured to be coupled to an antenna, the IC comprising:
a transceiver configured to communicate with RFID readers; and
a processor coupled to the transceiver and configured to:
receive, via the transceiver, an inventorying command, the inventorying command specifying one of a plurality of inventorying sessions;
select an encoding scheme based on the specified session;
generate a string for inclusion in a reply to the inventorying command;
adjust the string according to the selected encoding scheme, the encoding-adjusted string indicating the specified session used by the RFID IC; and
send the reply with the encoding-adjusted string indicating the specified session.
15. The RFID IC of claim 14 , wherein the string is one of a random number, a pseudorandom number, an algorithmically-generated value, a cryptographic value, and a content of an IC memory.
16. The RFID IC of claim 14 , wherein the encoding scheme is one of a parity encoding scheme, a checksum encoding scheme, a cyclic-redundancy-check encoding scheme, an error-detection encoding scheme, and an error-correction encoding scheme.
17. The RFID IC of claim 14 , wherein the processor is configured to select the encoding scheme by:
selecting a first encoding scheme if the specified session is one of a first session and a third session; and
selecting a second encoding scheme if the specified session is one of a second session and a fourth session.
18. The RFID IC of claim 17 , wherein the first encoding scheme has an odd parity and the second encoding scheme has an even parity.
19. The RFID IC of claim 14 , wherein the processor is configured to adjust the string according to the selected encoding scheme by at least one of:
adding a cyclic-redundancy-check to the string based on the selected encoding scheme; and
adjusting at least one bit of the generated string based on the selected encoding scheme.
20. The RFID IC of claim 14 , wherein the processor is further configured to:
receive, via the transceiver, an encoding-switch command instructing the IC to begin generating non-encoding-adjusted strings; and
in response to receiving the encoding-switch command:
generate a string for inclusion in a reply to a subsequent inventorying command; and
send the reply with the string without adjusting the string according to the selected encoding scheme.