RFID Huffman encoded commands

• US 7,562,083 B2
• Filed: 11/09/2005
• Issued: 07/14/2009
• Est. Priority Date: 11/07/2003
• Status: Active Grant

• Current Assignee: RUIZHANG TECHNOLOGY LIMITED COMPANY
• Original Assignee: Alien Technology Corporation
• Inventors: Smith, John Stephen, Carrender, Curtis L.
• Primary Examiner(s): Robinson; Greta L
• Assistant Examiner(s): Wilcox; James J
• Application Number:
  US11/271,628
• Publication Number:
  US 20060143163A1
• Time in Patent Office: 1,343 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing

Abstract

Methods and Apparatuses for RFID with Huffman encoded commands are provided. Each command of a plurality of commands is Huffman encoded. A rarely used command of the plurality of commands has more command bits than another command of the plurality of commands. The plurality of commands includes QueryA, QueryB, QueryRep, ACK, and NAK.

Claims

1. An RFID reader configured to perform an inventorying of RFID tags, the RFID reader comprising:

first and second antennas;

a transmitter coupled to the first antenna;

a receiver coupled to the second antenna; and

a microprocessor configured to transmit to a tag a plurality of Huffman encoded commands including a first command having a first number of first bits and a second command having a second number of second bits,

wherein the first number of the first bits of the first command of the plurality of encoded commands is greater than the second number of the second bits of the second command to improve bandwidth of the inventorying, wherein the first bits include third bits associated with a probability of reply by the tag, and wherein the first command is a first query command to query a subset of tags with a parameter, and the second command is a second query command to repeat querying the subset of tags with the parameter.

2. The RFID reader of claim 1 operating in a frequency range of about 900 megahertz.

3. The RFID reader of claim 1 wherein the microprocessor is a microcontroller.

4. The RFID reader of claim 1 further comprising dynamic random access memory and a memory controller that controls the operation of the memory.

5. The RFID reader of claim 1 further comprising a network interface.

6. The RFID reader of claim 5 wherein the network interface is an Ethernet interface.

7. The RFID reader of claim 1 wherein the plurality of encoded commands includes a handshake command, the second query command having fewer command bits than the handshake command.

8. The RFID reader of claim 7 wherein the second query command comprises 6 command bits and the handshake command comprises 7 command bits.

9. The RFID reader of claim 7 wherein the plurality of encoded commands further includes a NAK command preventing a state change in the tag, the NAK command having more command bits than both the query and handshake commands.

10. The RFID reader of claim 1 wherein the second command is a QueryRep command, and the first command is a QueryA command.

11. The RFID reader of claim 1 wherein the second command has fewer command bits than a NAK command.

12. The RFID reader of claim 11 wherein an ACK command has fewer command bits than the NAK command.

13. The RFID reader of claim 1 wherein the reader transmits a signal to the tag which signal is used by the tag to synchronize an internal clock in the tag.

14. An RFID tag comprising:

an antenna, the antenna configured to receive RF energy to power operation of the tag; and

an integrated circuit coupled to the antenna, the integrated circuit comprising;

a receiver; and

a state machine configured to implement a command protocol to perform an inventorying of RFID tags, the command protocol including a plurality of Huffman encoded commands including a first command having a first number of first bits and a second command having a second number of second bits,

wherein the first number of the first bits of the first command of the plurality of encoded commands is greater than the second number of the second bits of the second command of the plurality of encoded commands to improve bandwidth of the inventorying, wherein the first bits include third bits associated with a probability of reply by the RFID tag, and wherein the first command is a first query command to query a subset of tags with a parameter, and the second command is a second query command to repeat querying the subset of tags with the parameter.

15. The RFID tag of claim 14 wherein the tag receives a signal from a reader and uses the signal to synchronize an internal clock in the tag.

16. An RFID tag comprising:

an antenna, the antenna configured to receive RF energy to power operation of the tag; and

an integrated circuit coupled to the antenna, the integrated circuit comprising;

a receiver; and

logic configured to implement a command protocol to perform an inventorying of RFID tags, the command protocol including a plurality of Huffman encoded commands including a first command having a first number of first bits and a second command having a second number of second bits, wherein the first number of the first bits of the first command of the plurality of encoded commands is greater than the second number of the second bits of the second command of the plurality of encoded commands to improve bandwidth of the inventorying, wherein the first bits include third bits associated with a probability of reply by the RFID tag, and wherein the first command is a first query command to query a subset of tags with a parameter, and the second command is a second query command to repeat querying the subset of tags with the parameter.

17. The RFID tag of claim 16 wherein the plurality of encoded commands includes a handshake command, the second query command having fewer command bits than the handshake command.

18. The RFID tag of claim 17 wherein the second query command comprises 6 command bits and the handshake command comprises 7 command bits.

19. The RFID tag of claim 17 wherein the plurality of encoded commands further includes a NAK command preventing a state change in the tag, the NAK command having more command bits than both the query and handshake commands.

20. The RFID tag of claim 16 wherein the integrated circuit is configured for fluidic self-assembly.

21. The RFID tag of claim 16 wherein the integrated circuit further comprises a switch coupled to a transmitter and the receiver.

22. The RFID tag of claim 16 wherein the tag receives a signal from a reader and uses the signal to generate an internal clock in the tag.

23. A method of operating an RFID reader configured to perform an inventorying of RFID tags, the method comprising:

transmitting, through a first antenna, a first command of a plurality of Huffman encoded commands having a first number of first bits;

receiving a response from a tag; and

transmitting a second command of the plurality of Huffman encoded commands having a second number of second bits, wherein the second number of the second bits of the second command is greater than the first number of first bits of the first command to improve bandwidth of the inventorying, wherein the first command is a query command to query a subset of tags, and the second command is a second query command to repeat querying the subset of tags with the parameter.

24. The method of claim 23 further comprising transmitting a handshake command.

25. The method of claim 24 wherein the second query command comprises 6 command bits and the handshake command comprises 7 command bits.

26. The method of claim 24 wherein the plurality of encoded commands further includes a NAK command preventing a state change in a tag, the NAK command having more command bits than both the query and handshake commands.

27. The method of claim 23 wherein the first command is a QueryRep command and the second command is a QueryA command.

28. The method of claim 23 further comprising transmitting a NAK command.

29. The method of claim 23 further comprising transmitting a third command, the third command being an ACK command and having fewer bits excluding data bits than a NAK command.

30. The method of claim 23 wherein the reader includes the first antenna and a second antenna.

31. The method of claim 23 further comprising transmitting a signal to the tag, which signal is used by the tag to synchronize an internal clock in the tag.

32. A machine readable storage medium storing instructions which when executed on a data processing system configured to perform an inventorying of RFID tags, causes the system to transmit a plurality of Huffman encoded commands including a first command having a first number of first bits and a second command having a second number of second bits, wherein the first number of the first bits of the first command of the plurality of encoded commands is greater than the second number of the second bits of the second command to improve bandwidth of the inventorying, wherein the first bits include third bits associated with a probability of reply, and wherein the first command is a first query command to query a subset of tags with a parameter, and the second command is a second query command to repeat querying the subset of tags with the parameter.

33. The medium of claim 32 wherein the second command is a QueryRep command, and the first command is a QueryA command.

34. The medium of claim 32 wherein the second command is a QueryRep command, and wherein the plurality of encoded commands has a NAK command, wherein the QueryRep command has fewer command bits than the NAK command.

35. The medium of claim 34 wherein an ACK command of the plurality of encoded commands has fewer command bits than the NAK command.

36. The medium of claim 32 wherein the data processing system is coupled to a manufacturing tool.

37. The medium of claim 32 wherein the instructions further causes the system to transmit a signal to a tag, which signal is used by the tag to synchronize an internal clock in the tag.

38. An RFID reader configured to perform an inventorying of RFID tags, the RFID reader comprising:

an antenna;

a transmitter; and

a microprocessor configured to broadcast a plurality of commands including a first command having a first number of first bits and a second command having a second number of second bits with the antenna and transmitter, each command of the plurality of commands being Huffman encoded, whereby the first number of the first bits of the first command of the plurality of commands is greater than the second number of the second bits of the second command of the plurality of commands to improve bandwidth of the inventorying and command bits of any command is not a prefix for another command to comply with Huffman encoding, wherein the first bits includes third bits associated with a probability of reply, and wherein the first command is a first query command to query a subset of tags with a parameter, and the second command is a second query command to repeat querying the subset of tags with the parameter.

39. The reader of claim 38 further comprising an Ethernet network interface.

40. The reader of claim 38 wherein the reader transmits a signal to a tag which signal is used by the tag to synchronize an internal clock in the tag.