Anti-collision method for contactless electronic module

• US 20040012486A1
• Filed: 06/03/2003
• Published: 01/22/2004
• Est. Priority Date: 06/04/2002
• Status: Active Grant

• Current Assignee: Stmicroelectronics France (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Mani, Christophe
• Granted Patent: US 7,053,754 B2
• Time in Patent Office: Days
• 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 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot

Abstract

An anti-collision method to identify and select contactless electronic modules (MDL) by a terminal is provided. A module may generate a random identification number prior to a communication, and respond to a general or complementary identification request on a time slot that varies according to its identification number. A non-selected module may generate a new random identification number when it receives a complementary identification request. Thus, the time slot of a non-selected module provided in response to a complementary identification request is not statistically the same as its time slot in response to a previous identification request, and it varies according to its identification number (ID).

Claims

1. Anti-collision method to identify and select contactless electronic modules (MDL, TAG1-TAG8) by a terminal, in which:

prior to a communication, a module generates a random identification number (TD);

the terminal sends a general identification request (PCALL16) to trigger the sending of identification messages by the modules, and sends one or more non-nominative complementary identification requests (PCALL16) when identification messages collide;

a module is selected when it receives a select message (SELFCT(ID)) comprising its identification number;

in response to a general or complementary identification request, a non-selected module sends an identification message (R(ID)) comprising its identification number, when it reaches a determined time slot on a time scale;

characterized in that

a module responds to a general or complementary identification request on a time slot that varies according to its identification number (ID), and in that

a non-selected module generates a new random identification number when it receives a complementary identification request (PCALL16), such that the time slot of a non-selected module in response to a complementary identification request is not statistically the same as its time slot in response to a previous identification request, while varying according to its identification number (ID).

2. Method according to claim 1, in which a general identification request (PCALL16) is identical in format and in code to a complementary identification request (PCALL16).

3. Method according to one of claims 1 and 2, in which a module determines a time slot that is equal to a determined part (ID2) of its identification number, the determined part (ID2) comprising bits of determined rank the rank of which does not vary when the module responds to successive identification requests (PCALL16).

4. Method according to claim 3, in which the determined part (ID2) of the identification number of a module comprises least significant bits of the identification number (ID).

5. Method according to one of claims 1 to 4, in which, to generate a new random identification number, a module keeps a first part (ID1) of its current identification number, and randomly generates a second part (ID2) of the identification number.

6. Method according to claim 5, in which a module determines a time slot that is equal to the second part (ID2) of the identification number.

7. Method according to one of claims 5 and 6, in which the first part (ID1) of the identification number (ID) of a module is generated randomly by the module prior to a communication.

8. Method according to one of claims 5 and 6, in which the first part (ID1) of the identification number of a module is a constant datum logged in the module.

9. Method according to one of claims 1 to 8, in which the terminal also sends a complementary identification request (PCALL16) when it receives, in response to a previous complementary identification request, an identification message from a module that is not colliding with another identification message but which comprises an identification number (ID) already used by another module.

10. Method according to one of claims 1 to 9, in which a module is automatically activated (READY) when it is in the presence of a magnetic field sent by the terminal, and generates a random identification number when it is activated.

11. Method according to one of claims 1 to 10, in which the time slots on the time scale are marked by marking commands (PCALL16, SLOT-MARKER) sent by the terminal.

12. Method according to one of claims 1 to 11, in which a general identification request (PCALL16) forms a marking command of the first time slot on the time scale.

13. Method according to one of claims 11 and 12, in which a marking command (SLOT-MARKER(i)) comprises a time slot number (i), at least for time slots that are above a first time slot.

14. Method according to claim 13, in which the terminal sends marking commands in an order that does not correspond to an ascending rank of the time slots.

15. Method according to one of claims 1 to 14, in which the terminal only sends a complementary identification request after all the time slots of the time scale have been covered.

16. Method according to one of claims 1 to 15, in which, to start a communication, the terminal first of all sends an immediate identification request (PCALL0) to which the modules respond immediately, without time scale.

17. Method according to one of claims 1 to 16, in which a module comprises a selected state (SELECTED) and a deselected or deactivated state (DESELECTED, DEACTIVATED) to which the terminal may cause it to switch after selecting it, and in which a module in the selected state or in the deselected or deactivated state does not respond to a general or complementary identification request (PCALL16).

18. Contactless electronic module (MDL), comprising means (DMD, LMD) for sending and receiving messages without contact, means (CPU) for decoding received messages arranged to decode at least one general identification request (PCALL16), one non-nominative complementary identification request (PCALL16) and a select message (SELECTED(ID)), means for switching to a selected state (SELECTED) upon receiving a select message (SELECT(ID)) comprising an identification number (ID) of the module, the module being arranged to:

generate a random identification number (ID) before a communication;

upon receiving a general or complementary identification request, determine, if the module is not in the selected state, a time slot on a time scale then send, when the time slot is reached, an identification message (R(ID)) comprising the identification number (ID) of the module;

characterized in that it is arranged to

in response to a general (PCALL16) or complementary (PCALL16) identification request, determine a time slot that varies according to its identification number (ID); and

generate a new random identification number (ID) when it receives a complementary identification request (PCALL16), such that the time slot of the module in response to a complementary identification request is not statistically the same as its time slot in response to a previous identification request, while varying according to its identification number.

19. Module according to claim 18, arranged to decode a complementary identification request (PCALL16) identical in format and in code to a general identification request (PCALL16).

20. Module according to one of claims 18 and 19, arranged to determine a time slot that is equal to a determined part (ID2) of its identification number (ID), the determined part (ID2) comprising bits of determined rank the rank of which does not vary when the module responds to successive identification requests.

21. Module according to claim 20, in which the determined part (TD2) comprises least significant bits of the identification number of the module.

22. Module according to one of claims 18 to 21, arranged to generate a new identification number by keeping a first part (ID1) of its current identification number, and by randomly generating a second part (ID2) of the identification number.

23. Module according to claim 22, arranged to determine a time slot equal to the second part (ID2) of the identification number (ID), in response to a general or complementary identification request (PCALL16).

24. Module according to one of claims 22 and 23, in which the first part (ID1) of the identification number (ID) of a module is a constant datum logged in the module.

25. Module according to one of claims 22 and 23, in which the first part (ID1) of the identification number of a module is generated randomly by the module prior to a communication.

26. Module according to one of claims 22 to 25, arranged to determine a time slot that is equal to the second part (ID2) of the identification number (ID).

27. Module according to one of claims 18 to 26, arranged to switch automatically to an activated state (READY) when it is in the presence of a magnetic field of a determined frequency, and to generate an identification number (ID) when it switches to the activated state.

28. Module according to one of claims 18 to 27, arranged to decode marking commands (SLOT-MARKER) sent by the terminal, enabling the module to mark out time slots on the time scale.

29. Module according to claim 28, arranged to decode marking commands (SLOT-MARKER(i)) comprising a time slot number (i), at least for time slots that are above a first time slot.

30. Module according to one of claims 28 and 29, arranged to decode a general identification request (PCALL16) as a marking command of a first time slot on the time scale.

31. Module according to one of claims 18 to 30, arranged to decode an immediate identification request (PCALL0) and to send immediately, without time scale, in response to an immediate identification request (PCALL0), an identification message (R(ID)).

32. Module according to one of claims 18 to 31, comprising a deselected or deactivated state (DESELECTED, DEACTIVATED) to which it may switch after being in the selected state (SELECTED), the module being arranged to not respond to a general or complementary identification request when it is in the deselected or deactivated state.