Enhanced identification protocol for RFID systems

• US 7,486,172 B2
• Filed: 03/04/2005
• Issued: 02/03/2009
• Est. Priority Date: 08/07/2003
• Status: Active Grant

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Inventors: Heinrich, Harley, Pillai, Vijay, Ramamurthy, Shashi, Martinez, Rene
• Primary Examiner(s): Zimmerman; Brian
• Assistant Examiner(s): Syed; Nabil H
• Application Number:
  US11/073,145
• Publication Number:
  US 20050253687A1
• Time in Patent Office: 1,432 Days
• Field of Search: 340/10.2, 340/10.1, 340/10.3, 340/572.1, 340/573.1, 340/825, 342/42
• US Class Current: 340/10.2
• 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 7/10039 interrogator driven, i.e. synchronous

Abstract

An identification protocol that includes multiple identification methodologies is used to isolate and identify a radio frequency (RF) transponder. In accordance with a preferred embodiment of the present invention, the RF transponder includes a memory device, an RF front end, a random number generator (RNG), a counter, and a signal processing circuit connected thereto and programmed to operate in accordance with an identification protocol (or portions thereof). If multiple RF transponders are transmitting their ID numbers simultaneously, the radio frequency identification (RFID) base station may chose to resolve these conflicts later by transmitting the {a} Next_Cycle command, which moves the transponders back to a ready state. Alternatively, the {a} Fail command can be used to isolate and identify individual RF transponders. Once the transponder is isolated, it can be acknowledged and/or move to a 20 data_exchange state by transmitting a Read_New, FAK, PAK or AAK command, each one having unique characteristics.

Claims

1. A method of identifying a radio frequency (RF) transponder, comprising:

receiving a first set of identifying information from at least one RF transponder in an identification_transmitting state;

generating a first Fail command if said first set of identifying information is from more than one RF transponder, said first Fail command including a first_integer for identifying a number of times a routine is to be performed in response to receiving said first Fail command;

transmitting said first Fail command to said at least one RF transponder, said first Fail command prompting said at least one RF transponder to perform said routine said first_integer number of times, said routine comprising;

generating a random number, said random number being one of two integers; and

incrementing a counter by one if said random number is a particular one of said two integers;

receiving a second set of identifying information from each one of said at least one RF transponder that includes a counter that is equal to a second_integer after said routine is performed said first_integer number of times;

generating and transmitting a second Fail command if said second set of identifying information is from more than one RF transponder; and

transmitting an Isolation command if said second set of identifying information is from one RF transponder, said isolation command being adapted to move said one RF transponder from an identification_transmitting state to a data_exchange state, said one RF transponder in said data_exchange state being adapted to not respond to subsequently transmitted Fail commands.

2. The method of claim 1, wherein said step of receiving a first set of identifying information further comprises receiving at least one identification number from said at least one RF transponder.

3. The method of claim 1, further comprising the steps of:

estimating the number of RF transponders that transmitted said first set of identifying information; and

using said estimation to determine said first_integer.

4. The method of claim 1, wherein said step of generating a random number further comprises generating a random number, said random number being selected from a list of integers consisting of one and zero.

5. The method of claim 1, wherein said step of transmitting an isolation command further comprises transmitting a Read_New command that includes said second set of identifying information and a start address and is adapted to prompt (i) a first RF transponder in an identification_transmitting state and having a counter equal to said second_integer to transmit data starting at said start address and to move itself into said data_exchange state if said second set of identifying information matches an identification number stored on said first RF transponder and (ii) a second RF transponder in an identification_transmitting state and having a counter that is not equal to said second integer to decrement its counter by one.

6. The method of claim 1, wherein said step of transmitting an isolation command further comprises transmitting a Full_Acknowledgement command that includes at least said second set of identifying information and prompts (i) a first RF transponder in an identification_transmitting state and having a counter equal to said second_integer to move itself into said data_exchange state if said second set of identifying information matches a full identification (ID) number stored on said first RF transponder and (II) a second RF transponder in an identification transmitting state and having a counter that is not equal to said second_integer to decrement its counter by one, said full ID number being a unique identifier of said first RF transponder.

7. The method of claim 1, wherein said step of transmitting an isolation command further comprises transmitting a Partial_Acknowledgement command that includes at least said second set of identifying information and prompts (i) a first RF transponder in an identification_transmitting state and having a counter that is equal to said second_integer to move itself into said data_exchange state if said second set of identifying information matches a compact identification (ID) number stored on said first RF transponder and (ii) a second RF transponder in an identification_transmitting state and having a counter that is not equal to said second integer to decrement its counter by one, said compact ID number being smaller than a full ID number, which is a unique identifier, and usable to distinguish said first RF transponder from at least one other RF transponder.

8. The method of claim 1, wherein said step of transmitting an isolation command further comprises transmitting an Ambiguous_Aacknowledgement command that does not include said second set of identifying information and prompts (i) a first RF transponder in an identification_transmitting state and having a counter equal to said second_integer to move itself into said data_exchange state and (ii) a second RF transponder in an identification_transmitting state and having a counter not equal to said second_integer to decrement its counter by one.

9. A method of identifying a radio frequency (RF) transponder, comprising:

transmitting an identification command to a plurality of RF transponders in an identification_transmitting state, said identification command being adapted to prompt each one of said plurality of RF transponders having a counter equal to a first_integer to transmit identifying information;

receiving said identifying information;

transmitting an isolation command if said identifying information is intelligible and identified as being transmitted from a single RF transponder, wherein said isolation command is adapted to prompt (i) said single RF transponder to move itself from an identification_transmitting state to a data_exchange state, which prevents said single RF transponder from responding to subsequently transmitted identification commands, and (ii) said plurality of RF transponders, with the exception of said single RF transponder, to decrement their counters by a second_integer; and

generating a Fail command if said identifying information is identified as being transmitted from more than one RF transponder, said Fail command including a second_integer for identifying a number of times a routine is to be performed in response to receiving said Fail command; and

transmitting said Fail command to said plurality of RF transponders, said Fail command prompting said each one of said plurality of RF transponders to perform said routine, said routine comprising the steps of;

generating a random number, said random number being one of two integers; and

incrementing a counter by one if said random number is a particular one of said two integers; and

transmitting identifying information if said counter is equal to said first_integer after said routine is performed said second_integer number of times.

10. A radio frequency identification (RFID) system comprising:

a radio frequency (RF) transponder and a RFID base station, said RF transponder comprising;

a front end circuit adapted to receive and transmit RF signals;

an antenna electrically connected to said front end circuit;

a random number generator (RNG);

a counter; and

a signal processing circuit electrically connected to said front end circuit, said RNG and said counter, and adapted to;

determine whether a Fail command has been received, said Fail command including at least a first_integer for identifying a number of times a routine is to be performed in response to receiving said Fail command;

perform said routine said first_integer number of times in response to receiving said Fail command if said RF transponder is in an identification_transmitting state, said routine comprising;

a first step of running said RNG to produce a result; and

a second step of incrementing said counter by one if a first RNG result is produced; and

transmitting identifying information if said counter is equal to a second_integer after said routine is performed said first_integer number of times.

11. The RFID system of claim 10, wherein said signal processing circuit is further adapted to:

determine whether an Isolation command has been received;

move said RF transponder from said identification_transmitting state to a data_exchange state if said counter is equal to said second_integer, said signal processing circuit being adapted to not respond to said Fail command when said RF transponder is in said data_exchange state; and

decrement said counter by one if said counter is not equal to said second_integer.

12. The RFID system of claim 10, wherein said signal processing circuit is further adapted to receive and respond to at least two Isolation commands, said two Isolation commands being selected from a list of commands consisting of a Ready_New command, a Full_Acknowledgement command, a Partial_Acknowledgement command, and an Ambiguous_Acknowledgement command.

13. The RFID system of claim 10, wherein said signal processing circuit is further adapted to:

determine whether an Next_Cycle command has been received;

move said RF transponder from said identification_transmitting state to a ready state if said counter is equal to said second integer, said signal processing circuit being adapted to not respond to said Fail command and said Isolation command when said RF transponder is in said ready state.

14. The RFID system of claim 10, further comprising a single device that includes said RNG and said counter.