Method for managing collisions in a contactless data exchanging system

• US 6,646,543 B1
• Filed: 11/22/1999
• Issued: 11/11/2003
• Est. Priority Date: 03/03/1997
• Status: Expired due to Term

• Current Assignee: Societe Anonyme D.B.A.
• Original Assignee: Regie Autonome Des Transports Parisiens
• Inventors: Grieu, Francois, Mardinian, Grégory
• Primary Examiner(s): Lieu, Julie
• Application Number:
  US09/380,486
• Time in Patent Office: 1,450 Days
• Field of Search: 340/572, 340/10.2, 340/10.3, 340/10.32, 340/10.4, 340/10.41, 340/572.4, 340/572.2
• 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 7/10059 transponder driven

Abstract

A method handles collisions in a data interchange between portable objects and at least one data transceiver. The method includes the steps of the transceiver transmitting to said plurality of portable objects general call messages, each including a collision probability modulation parameter. Each portable object conditionally transmits to the transceiver a general call response with a probability of less than 100% as a function of the collision probability modulation parameter and having a specific identifier. The transceiver receives a general call response message, and in the absence of any collision between said message and a message transmitted by another portable object, a specific data communication link is established. Otherwise the method returns to the first step and repeats, optionally modifying the dynamic range of the probability modulation parameter.

Claims

1. For use in a system of interchanging data between a plurality of portable objects and at least one data transceiver terminal suitable for cooperating with portable objects simultaneously present in a field of action of the terminal, the terminal comprising circuitry configured to perform the following:

store a collision probability modulation parameter (PMP), the value of which is a function of a mean number of said portable objects likely to be found in a field of action of said terminal;

transmit a general call message to the portable objects, the general call message including said PMP;

receive a general response message from each of the portable objects determined to respond to the general call message, each of the general response messages including an identifier uniquely identifying the respective portable object transmitting the general response message;

in the absence of a collision between the general response messages of portable objects, establish a specific data communication link between the terminal and each portable object transmitting the general response message, respectively; and

determine a collision has occurred between the general response messages of portable objects when the general response message is not received from any of the portable objects and transmit the general call message again.

2. The terminal of claim 1, wherein the circuitry is configured to modify the probability modulation parameter of before the general call response message is transmitted again.

3. The terminal of claim 2, wherein the circuitry is configured to decrease the probability modulation parameter when a collision is determined.

4. The terminal of claim 1, wherein when a collision is determined, the circuitry is configured to modify the probability modulation parameter so that the probability of any of the portable objects transmitting the general call response message is less than 100%.

5. A system where data is interchanged between a plurality of portable objects and a data transceiver terminal suitable for cooperating with the plurality of portable objects simultaneously present in a field of action of the terminal, comprising:

means for setting in the terminal a collision probability modulation parameter (PMP), the value of which is a function of a mean number of said portable objects likely to be found in a field of action of said terminal;

means for transmitting a general call message from the terminal to the portable objects, the general call message including said PMP set in the terminal;

means for determining which portable objects will respond to the general call message based on the PMP;

means for transmitting a general response message by each portable object determined to respond to the general call message, each of the general response messages including an identifier uniquely identifying the respective portable object transmitting the general response message;

upon the one terminal receiving the general call message and the absence of a collision between the general response messages of portable objects, means for establishing a specific data communication link between the one terminal and each of the plurality of portable objects transmitting the general call message;

wherein when the terminal determines at least one of a collision between the general response messages of portable objects and not receiving the general call message from any of the plurality of objects, the means for transmitting is configured to transmit another subsequent general call message.

6. The system of claim 5, further comprising:

means for modifying the probability of the general call response message being transmitted.

7. The system of claim 5, further comprising:

means for decreasing the probability of the general call response message being transmitted in an event of a collision.

8. The system of claim 5, each of the portable objects comprising:

means for producing a pseudo-random value and comparing said pseudo-random value with the received probability modulation parameter.

9. The system of claim 8, wherein the probability modulation parameter includes a first field containing data representative of a predetermined type of terminal, and a second field containing data for modifying the probability modulation parameter.

10. The system of claim 5, the terminal further comprising:

means for generating a control message (COM) including the identifier specific to the respective portable object, as received by the terminal in response to the general call message, and a communications channel number;

means for sending said control message from the terminal to the respective portable object and continuing a data interchange on the channel identified by the communications channel number.

11. The system of claim 10, further comprising:

a plurality of terminals,

wherein the channel number includes a data item specific to the terminal which established a link with the portable object, said data item differing between adjacent ones of the terminals.

12. The system of claim 5, wherein the probability modulation parameter is dynamically modifiable from one general call message to another subsequent general call message.

13. The system of claim 5, wherein the plurality of portable objects are badges.

14. A method of controlling collisions in a system of interchanging data between a plurality of portable objects and at least one data transceiver terminal suitable for co-operating with the plurality of portable objects simultaneously present in a field of action of the at least one terminal, the method comprising the following steps:

a) setting in the terminal a collision probability modulation parameter (PMP), the value of which is a function of a mean number of said portable objects likely to be found in a field of action of said terminal;

b) transmitting a general call message from the at least one terminal to the plurality of portable objects, the general call message including said PMP set in the terminal;

c) receiving a general response message from each of the plurality of portable objects determined to respond to the general call message, each of the general response messages including an identifier uniquely identifying the respective portable object transmitting the general response message;

d) upon the at least one terminal determining the general response message and the absence of a collision between the general response messages of portable objects, establishing a specific data communication link between the at least one terminal and each of the plurality of portable objects transmitting the general response message, respectively, and repeating steps b) through d), for a new iteration;

e) upon the at least one terminal determining at least one of a collision between the general response messages of portable objects and not receiving the general response message from any of the plurality of objects, repeating steps (b) through (e) for a new iteration.

15. The method of claim 14, wherein the probability modulation parameter of the general call response message being transmitted is modified on each new consecutive iteration.

16. The method of claim 15, wherein the probability modulation parameter of the general call response message being transmitted is decreased in an event of a collision on the respective new iteration.

17. The method of claim 14, wherein at least within iterations following step d in an event of a collision subsequent to a first transmission of the general call message, the probability modulation parameter is transmitted by the at least one terminal so as to define the probability of less than 100% for transmission of the general call response message by any of the plurality of portable objects.

18. A method of controlling collisions in a system of interchanging data between a plurality of portable objects and at least one data transceiver terminal suitable for co-operating with the plurality of portable objects simultaneously present in a field of action of the at least one terminal, the method comprising the following steps:

a) setting in the terminal a collision probability modulation parameter (PMP), the value of which is a function of a mean number of said portable objects likely to be found in a field of action of said terminal;

b) transmitting a general call message from the at least one terminal to the plurality of portable objects, the general call message including said PMP set in the terminal;

c) determining which ones of the plurality of portable objects will respond to the general call message based on the PMP;

d) transmitting a general response message by each of the plurality of portable objects determined to respond to the general call message, each of the general response messages including an identifier uniquely identifying the respective portable object retransmitting the general response message;

e) upon the at least one terminal receiving the general response message and the absence of a collision between the general response messages of portable objects, establishing a specific data communication link between the at least one terminal and each of the plurality of portable objects transmitting the general response message, respectively, and repeating steps b) through e), for a new iteration;

f) upon the at least one terminal determining at least one of a collision between the general response messages of portable objects and not receiving the general response message from any of the plurality of objects, repeating steps b) through f) for a new iteration.

19. The method of claim 18, wherein the probability of the general call response message being transmitted is modified on each new consecutive iteration in at least one of step e) and f).

20. The method of claim 19, wherein the probability of the general call response message being transmitted is decreased in an event of a collision on the respective new iteration following step f).

21. A method of claim 18, wherein at least within iterations following step f in an event of a collision subsequent to a first transmission of the general call message, the probability modulation parameter (PMP) is transmitted by the at least one terminal so as to define the probability of less than 100% for transmission of the general call response message by any of the plurality of portable objects.

22. The method of claim 21, wherein when the respective portable object receives the probability modulation parameter (PMP), the respective portable object produces a pseudo-random value and compares said pseudo-random value with the received probability modulation parameter.

23. The method of claim 22, wherein:

the probability modulation parameter includes a first field containing fixed data representative of a predetermined type of terminal, and a second field containing specific data for modulating the probability;

in step c), the fixed data is subjected to a prior comparison with corresponding data contained in the respective portable object; and

the pseudo-random value is generated and the transmission by any of the plurality of portable objects of the general response message of step d) is performed only if the prior comparison has also given rise to a “

true”

result.

24. The method of claim 18, wherein in step e), establishing the specific link includes:

generating a control message (COM) including both the identifier specific to the respective portable object as received by the at least one terminal in response to the general call message, and an unambiguous communications channel number;

sending said control message from the at least one terminal to the respective portable object, and

continuing the data interchange on the channel.

25. The method of claim 24, wherein for a portable object simultaneously in the fields of action of a plurality of terminals, the channel number includes a data item specific to the respective terminal which has established the link with the respective portable object, said data item differing between adjacent terminals.

26. The method of claim 18, wherein:

the probability modulation parameter is a parameter that is dynamically modifiable from one general call message to a subsequent general call message;

the at least one terminal includes means operative in step f) to discriminate between an absence of the general call response message being received and a non-compliant message being received, particularly in an event of a collision between general response messages transmitted by different portable objects;

in step f), in a presence of a non-compliant message, the probability modulation parameter is modified before returning to step b), with the modification decreasing the probability of a “

true”

result being obtained in the subsequent step c), and

in step e), in the absence of the at least one terminal receiving the general call response message, the probability modulation parameter is modified prior to returning to step b) increasing the probability of obtaining a “

true”

result in the subsequent step c).

27. The method of claim 18, wherein after each comparison of step c), the respective portable object counts a number of consecutive “

false”

result produced in response to the respective general call messages transmitted by the at least one terminal, and forces a response message to be transmitted to the respective general call message whenever a corresponding count has reached a predetermined threshold, even when a protocol defined by the probability modulation parameter requires a random response.

28. A The method of claim 18, wherein the plurality of portable objects are badges.