Method of communication in a radio frequency identification system

• US 20030052161A1
• Filed: 09/18/2001
• Published: 03/20/2003
• Est. Priority Date: 09/18/2001
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rakers, Patrick L., Rachwalski, Richard Stanley, Collins, Timothy James, Bushman, Michael L.
• Granted Patent: US 6,763,996 B2
• Time in Patent Office: Days
• US Class Current: 235/375
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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

Abstract

A first request is transmitted to activate a set of tags in a first state. A first set of data symbols is received. In response to receiving the first set of data symbols, a first acknowledgement symbol transmitted. An acknowledgement symbol is transmitted in response to each subsequent set of data symbols received. A second request is transmitted to activate a second set of tags in a second state when a set of data symbols is not received within a predetermined time, wherein the first state is different from the second state.

Claims

1. A method comprising the steps of:

(a) identifying a plurality of data fields;

(b) transmitting a data symbol comprising a first set of data;

(c) maintaining a data field from which the data symbol was transmitted;

(d) receiving an acknowledgement symbol comprising a second set of data;

(e) comparing the first set of data to the second set of data; and

(f) if the first set of data is equivalent to the second set of data, repeating steps b-f until data transmission is complete;

otherwise, temporarily suspending data transmission.

2. The method of claim 1 further comprising the step of maintaining the data field for a predetermined period of time when power is removed and subsequently re-applied.

3. The method of claim 1 further comprising the step of defaulting to a first data field when power is removed and subsequently re-applied.

4. The method of claim 1 further comprising the steps of, if the first set of data is not equivalent to the second set of data:

receiving a request for devices temporarily suspended in a given data field to resume data transmission;

if the data field that was maintained is equivalent to the given data field identified in the request, repeating steps b-f, starting with a first symbol in the data field that was maintained; and

if the data field is not equivalent to the given data field identified in the request, continuing to temporarily suspend data transmission.

5. The method of claim 1 further comprising the step of becoming inactive when data transmission is complete.

6. The method of claim 1 further comprising the steps of:

initializing to a first data field upon power-up;

receiving a request for devices in a given data field to transmit data; and

becoming active only if the first data field is equivalent to the given data field identified in the request.

7. A method comprising the steps of:

(a) transmitting a request to activate a set of tags in a first state;

(b) receiving a set of data symbols;

(c) in response to receiving the set of data symbols, transmitting an acknowledgement symbol;

(d) continuing to transmit an acknowledgement symbol in response to each set of data symbols received, and when a predetermined number of sets of data symbols is received, repeating steps a-d; and

(e) when a set of data symbols is not received in step b, transmitting a second request to activate a set of tags in a second state, wherein the first state is different from the second state.

8. The method of claim 7 further comprising the step of, after the step of transmitting the second request, looping through steps b-e.

9. A method comprising the steps of:

transmitting a request to activate a set of tags in a first state;

receiving a set of data symbols;

in response to receiving the set of data symbols, transmitting an acknowledgement symbol;

continuing to transmit an acknowledgement symbol in response to each subsequent set of data symbols received;

transmitting at least a second request to activate a set of tags in a second state, wherein the first state is different from the second state.

10. The method of claim 9 further comprising the step of transmitting an excitation signal.

11. The method of claim 9 further comprising the step of copying at least a portion of data represented by each acknowledgement symbol into a storage device.

12. The method of claim 9 further comprising the steps of:

copying at least a portion of data represented by each acknowledgement symbol into a first storage device; and

when the first storage device contains a predetermined amount of data, copying the predetermined amount of data into a first location of a second storage device.

13. The method of claim 10 further comprising the step of clearing at least a portion of the first storage device upon transmitting a request to activate a group of radio frequency identification tags in a given state.

14. The method of claim 10 further comprising the step of copying at least a portion of data represented by each acknowledgement symbol transmitted after the request into the portion of the first storage device that was cleared.

15. A method comprising the steps of:

(a) identifying a plurality of data fields;

(b) transmitting a request;

(c) transmitting a data symbol;

(d) maintaining a data field from which the data symbol was transmitted; and

(e) if the data symbol is acknowledged, repeating steps c-e;

otherwise, returning to a beginning of a data field and repeating steps b-e.

16. A method comprising the steps of:

(a) identifying a plurality of data fields, each data field having a set of field symbols and each field symbol having a first set of data;

(b) receiving a data symbol comprising a second set of data;

(c) identifying a field symbol corresponding to the data symbol in a location;

(d) if the first set of data of the field symbol is equivalent to the second set of data of the data symbol, transmitting an acknowledgement symbol and repeating steps b-d;

otherwise, temporarily suspending data transmission and returning to a beginning of the data field containing the field symbol corresponding to the data symbol in the location.

17. A method comprising the steps of:

(a) identifying a plurality of data fields;

(b) transmitting a request;

(c) transmitting a data symbol corresponding to a position in a data field;

(d) maintaining the data field from which the data symbol was transmitted;

(e) if the data symbol is acknowledged, repeating steps c-f;

otherwise, transmitting a second data symbol corresponding to the position in the data field; and

(f) if the second data symbol is acknowledged, repeating steps c-f;

otherwise, returning to a beginning of the data field and repeating steps b-f.