Time division multiplexed batch mode item identification system

• US 5,539,394 A
• Filed: 06/20/1995
• Issued: 07/23/1996
• Est. Priority Date: 03/16/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Posey, Hollis P., Harris, Richard H., Cato, Robert T.
• Primary Examiner(s): Bowler, Alyssa H.
• Assistant Examiner(s): Rinehart, Mark H.
• Application Number:
  US08/493,847
• Time in Patent Office: 399 Days
• Field of Search: 340/825.35, 340/825.54, 340/825.71, 340/825.72, 340/825.73, 340/825.74, 340/572, 340/508
• US Class Current: 340/10.32
• CPC Class Codes: G06K 17/0022 arrangements or provisious for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• 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 7/10059 transponder driven
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G07G 1/0054 with control of supplementary check-parameters, e.g. weight or number of articles
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/246 Check out systems combined with EAS, e.g. price information stored on EAS tag anti-theft systems in point of sale systems G07G3/003
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: G08B 13/2482 EAS methods, e.g. description of flow chart of the detection procedure
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags
• CPC Class Codes: G08B 13/2488 Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver

Abstract

Apparatus and method are disclosed for communicating between a central location and a plurality of identification tags or labels located in a container or in a space without separately passing each tag or labeled product through a read station. The disclosure includes use of hashing to reduce the amount of time needed to read the possible tags in the space. Reading is accomplished using radio communication with a combination of broadcast and time division multiplex architectures.

Claims

1. A method of reading a plurality of identification tags in a read volume, each tag having a chip, each chip having data storage, logic and communication circuits said storage containing tag identification information comprising the steps of:

1) broadcasting a start command to all of said tags, said start command indicating to said tags that their tag identification information needs to be transmitted;

2) broadcasting a hashing base number to all of said tags from which each tag, to which it has been indicated that their tag identification information needs to be transmitted, use the hashing base number, said tag identification information and a hashing algorithm to determine which of a plurality of time slots to transmit said tag identification information;

3) receiving null and tag identification information transmitted by said tags in the plurality of time slots;

4) detecting a collision state when a plurality of tags transmit tag identification information in a single time slot;

5) detecting a clear signal state when tag identification information from only one tag is received in a time slot;

6) transmitting clear signal acknowledgment information to those tags which transmitted tag identification information in a time slot in which no other tag transmitted, said acknowledgment information indicating to said those tags that their tag identification information need not be retransmitted;

7) repeating steps 2, 3, 4, 5, and 6 using a newly generated hashing base number for each iteration, as the hashing base number until a collision state is not detected; and

8) processing the received tag identification information.

2. The method of claim 1 wherein step 8 includes the steps of:

1) using the tag identification information to identify the product to which the related tag was attached by accessing storage to retrieve product information and price information;

2) tabulating total purchases;

3) accepting payment; and

4) adjusting inventory records.

3. The method of claim 2 wherein said storage is physically located on said related tag and step 1 of claim 2 further comprises the steps of:

1) transmitting a read storage command to said related tag; and

2) receiving from said tag, product information and price related information of the product to which said related tag is attached.

4. The method of claim 1 wherein step 6 further comprises the steps of:

1) transmitting a receive acknowledgement command to all of said tags, said receive acknowledgement command defining the start of a new set of time slots and

2) transmitting tag identification information to a tag for which a clear signal was detected in a unique time slot of said new set of time slots, said unique time slot being the time slot in which later communication may be conducted with said tag.

5. The method of claim 4 wherein said processing step 8 of claim 1 further comprises:

1) broadcasting a group read product data command to all of said tags;

2) receiving product information and price information from said tag in said unique time slot described in step 2 of claim 4

3) receiving product information and price information from others of said tags in other time slots of said new set of time slots;

4) tabulating total purchases;

5) accepting payment, and

6) adjusting inventory records.

16. The method of claim 1 wherein step 6 said acknowledgement information contains tag identification information for those tags which transmitted tag identification information in a time slot in which no other tag transmitted.

18. The method of claim 1 wherein step 1 the start command provides identification of the hashing algorithm that is used to determine the time slot in which to transmit.

6. The method of conveying data from a tag, said tag having data storage, logic and communication circuits said storage containing tag identification information comprising the steps of:

1) receiving a start command;

2) receiving a hashing base number;

3) hashing said hashing base number with said tag'"'"'s tag identification information to identify a time slot;

4) transmitting said tag identification information in said identified time slot, and

5) repeating steps 2, 3 and 4 until a clear signal acknowledgement containing said tag identification information is received.

7. The method of claim 6 further comprising the steps of:

1) receiving a read storage command;

2) transmitting from said tag, product information and price information of the product to which said tag is attached.

8. Apparatus for reading a plurality of identification tags, each tag having data storage, logic and communication circuits, said apparatus comprising:

communication means for transmitting signals to and receiving signals from said plurality of tags;

processor means connected to said communication means and to a storage means;

said processor executing programs stored in said storage means and processing data including data stored in said storage means;

said programs including a broadcast start command means for broadcasting a start command to all of said tags;

said programs including first programmed means for broadcasting a hashing base number to all of said tags;

said programs including second programmed means for receiving null and tag data in a plurality of time slots;

said programs including third programmed means for detecting a collision state when a plurality of tags transmit tag data in a single time slot;

said programs including fourth programmed means for detecting a clear signal state when tag data from only one tag is received in a time slot;

said programs including fifth programmed means for transmitting clear signal acknowledgement information to those tags which transmitted tag data in a time slot in which no other tag transmitted, said acknowledgement information indicating to said those tags that their tag data need not be retransmitted;

said programs including a programmed control means for reactivating said second, third, fourth and fifth programmed means until a collision state is not detected;

said programs including programmed transaction processing means for processing said received tag data.

9. The apparatus of claim 8 wherein said programmed transaction means further comprises:

storage access means responsive to said tag data to identify the product to which the related tag was attached by accessing storage to retrieve product information and price information;

summing means for tabulating total purchases;

means for accepting payment, and

means for updating inventory records.

10. The apparatus of claim 9 wherein said storage is physically located on said related tag and said storage access means further comprises:

means for controlling said communication means to transmit a read storage command to said related tag;

means for controlling said communication means to receive from said tag, product information and information of the product to which said related tag is attached.

11. The apparatus of claim 8 wherein said fifth programmed means further comprises:

means for controlling said communication means to transmit a receive acknowledgement command to all of said tags, said receive acknowledgement command defining the start of a new set of time slots;

means for controlling said communication means to transmit tag identification information to a tag for which a clear signal was detected in a unique time slot of said new set of time slots, said unique time slot being the time slot in which later communication may be conducted with said tag.

12. The method of claim 11 wherein said programmed transaction processing means further comprises:

programmed means for controlling said communication means to broadcast a read product data command to all of said tags;

programmed means for controlling said communication means to receive product information and price information from said tag in said unique time slot;

programmed means for controlling said communication means to receive product information and price information from others of said tags in other time slots of said new set of time slots;

programmed means for controlling said processor means to tabulate total purchases;

programmed means for controlling said processor means to accept payment, and

programmed means for controlling said processor means to adjust inventory records.

17. The apparatus of claim 8 wherein said tag data includes tag identification information and said clear signal information transmitted by said fifth programmed means includes tag identification data for those tags which transmitted tag data in a time slot in which no other tag transmitted.

13. An identification tag comprising:

data storage;

logic connected to said data storage;

communication circuits connected to said logic;

said logic including first means for responding to a start command;

said logic including second means for responding to a hashing base number;

said logic including third means for calculating a time slot using said hashing base number, a hashing algorithm and data from said storage means;

said logic including fourth means for controlling said communication circuits to transmit data in said time slot;

said logic including fifth means for receiving an acknowledgement;

said acknowledgement indicating to said tag that its data need not be retransmitted, and

said logic including control means for reactivating said second, third, fourth and fifth means until an acknowledgement is received.

14. The apparatus of claim 13 wherein said data storage means includes storage for product information and price information, said control means being responsive to a read command to control said communication means to transmit said information.

15. The apparatus of claim 13 wherein said fifth means further comprises:

means for controlling said communication means to receive a receive acknowledgement command, said receive acknowledgement command defining the start of a new set of time slots; and

said logic further comprises sixth means responsive to said acknowledgement command to receive data in a unique time slot of said new set of time slots, said unique time slot being the time slot in which later communication may be conducted with said tag.

19. A method of reading a plurality of identification tags at a Point of Sale checkout counter, each tag associated with an item to be purchased, each tag having a chip, each chip having data storage, logic and communication circuits said storage containing tag identification information comprising the steps of:

1) broadcasting a start command and a hashing base number to all of said tags, said start command indicating to said tags that their tag identification information needs to be transmitted;

2) hashing, in each tag to which it has been indicated that their tag identification information is to be transmitted, using the hashing base number and the tag identification information to determine which of a plurality of time slots to transmit said tag identification information;

3) receiving null and tag identification information transmitted by said tags in the plurality of time slots;

4) detecting a collision state when a plurality of tags transmit tag identification information in a single time slot;

5) detecting a clear signal state when tag identification information from only one tag is received in a time slot;

6) transmitting clear signal acknowledgment information to those tags which transmitted tag identification information in a time slot in which no other tag transmitted, said acknowledgment information indicating to said those tags that their tag identification information need not be transmitted;

7) repeating steps 2, 3, 4, 5, and 6 with a newly generated hashing base number as the hashing base number in each iteration, until a collision state is not detected; and

8) processing the received tag identification information.

20. The method of claim 19 wherein said newly generated hashing base number is generated from said broadcast hashing base number in each of the tags.