Method of managing collisions in a non-contact data interchange system

• US 6,690,263 B1
• Filed: 12/06/1999
• Issued: 02/10/2004
• Est. Priority Date: 01/15/1998
• Status: Expired due to Term

• Current Assignee: La Regie Autonome Des Transports Parisiens, Societe Anonyme D.B.A.
• Original Assignee: Innovatron Electronique
• Inventors: Grieu, Francois
• Primary Examiner(s): Lieu, Julie
• Application Number:
  US09/381,019
• Time in Patent Office: 1,527 Days
• Field of Search: 340/572.1, 340/10.2, 340/10.3, 340/10.32, 340/10.4, 340/10.41, 340/572.4
• US Class Current: 340/10.4
• 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
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles

Abstract

A method manages collisions in a system for interchanging data between portable objects and at least one terminal suitable for co-operating with a plurality of the portable objects simultaneously. The terminal sends out call messages to the portable objects. A portable object conditionally sends a message to the terminal in response to the call with a probability that may be less than 100%, the response containing an identifier specific to the portable object. The receiver receives a response from an identified portable object and in absence of the response colliding with a response sent out by another portable object, a specific data communication link is established between the terminal and the identified portable object. The portable object modulates the probability of response over time depending on whether or not it has itself already responded previously to a call message sent out by the terminal.

Claims

1. A method of managing collisions in a system of interchanging data between a plurality of portable objects and a data transceiver terminal suitable for cooperating with the portable objects simultaneously present in a communicating range of the terminal, the method comprising the following steps:

a) transmitting call messages from the at least one terminal to the plurality of portable objects, at least one of the terminal, the call messages, and the portable objects including a probability modulation parameter (PMP), the probability modulation parameter corresponding to a probability that at least one of the portable objects will respond to the call messages, wherein the one portable object changes the probability modulation parameter based on whether the one portable object previously responded to the call messages transmitted by the terminal;

b) using the PMPs corresponding to those portable objects, determining which ones of the portable objects will respond to the call messages;

c) transmitting a response message from each portable object determined in step (b) to respond to the call messages, each response including an identifier uniquely identifying the respective portable object transmitting the response message;

d) upon the terminal receiving at least one response message and determining an absence of a collision between the respective response messages of portable objects, establishing a specific data communication link between the at least one terminal and each of portable object transmitting the response message, respectively, and repeating steps (a) through (d);

e) upon the terminal determining a collision between the response messages of portable objects and not receiving the response message from any of the portable objects, repeating steps (a) through (d); and

wherein the terminal sends out two types of call messages;

query messages initializing the probability modulation parameter and marker messages sent out after the query messages for causing the portable objects optionally and in the absence of any prior response to the call messages to modify the probability modulation parameter upon receiving one of the marker messages.

2. The method of claim 1, wherein the probability modulation parameter is sent out by the at least one terminal.

3. The method of claim 1, wherein the probability modulation parameter is increased over time if the portable object has not previously responded to a call message sent out by the at least one terminal.

4. The method according to claim 3, wherein the probability modulation parameter is increased up to a 100% probability of a response by at least one of the plurality of portable objects over a finite time interval or after a finite number of call messages has been sent out by the at least one terminal.

5. The method of claim 1, wherein the portable object reinitializes said probability modulation parameter after responding to the respective call message sent out by the at least one terminal.

6. The method of claim 1, wherein the portable objects respond selectively in time slots following reception of the marker messages.

7. The method of claim 6, wherein selection between time intervals is determined in a probabilistic manner by drawing one of a random number and a pseudo-random number in the portable object on receiving one of the query messages.

8. The method of claim 1, wherein the at least one terminal sends out one of the query messages again on detecting a collision.

9. The method of claim 1, wherein the at least one terminal reduces a time interval between two successive call messages in the absence of any response from an identified portable object within a predetermined period.

10. A method of managing collisions in a system of interchanging data between a plurality of portable objects and a data transceiver terminal suitable for cooperating with the portable objects simultaneously present in a communicating range of the terminal, the method comprising the following steps:

a) transmitting call messages from the terminal, at least one of the terminal, the call messages, and the portable objects including a probability modulation parameter (PMP), the probability modulation parameter corresponding to a probability that one of the portable objects will respond to one of the call messages, wherein the one portable object changes the probability modulation parameter based on whether the one portable object previously responded to one of the call messages transmitted by the terminal;

b) using the PMPs corresponding to those portable objects, determining which ones of the portable objects will respond to the call messages;

c) transmitting a response message from each of portable object determined in step (b) to respond to the call messages, each response message including an identifier uniquely identifying the respective portable object transmitting the response message;

d) upon the terminal receiving at least one response message and determining an absence of a collision between the respective response messages of portable objects, establishing a specific data communication link between the terminal and each portable object transmitting the response message, respectively, and repeating steps (a) through (d);

e) upon the terminal determining a collision between the response messages of portable objects and not receiving the response message from any of the portable objects, repeating steps (a) through (d); and

wherein the call message includes a field representing one or more types of applications managed by the terminal, the portable object contains in its memory one or more types of applications for which the portable object is intended, and the portable object compares the application types received with the call message with the application types contained in memory of the portable object, and inhibits responding in step b) whenever the comparison detects no application-type in common.

11. A method of managing collisions in a system of interchanging data between a plurality of portable objects and a data transceiver terminal suitable for cooperating with portable objects simultaneously present in a communicating range of the terminal, the method comprising the following steps:

a) transmitting call messages from the terminal, at least one of the terminal, the call messages, and the plurality of portable objects including a probability modulation parameter (PMP), the probability modulation parameter corresponding to a probability that one of the portable objects will respond to one of the call messages, wherein the one portable object changes the probability modulation parameter based on whether the at least one portable object previously responded to one of the call messages transmitted by the terminal;

b) using the PMPs corresponding to those portable objects, determining which ones of the portable objects will respond to the call messages;

c) transmitting a response message by each plurality of portable objects determined in step (b) to respond to the call messages, each response message including an identifier uniquely identifying the respective portable object transmitting the response message;

d) upon the terminal receiving at least one response message and determining an absence of a collision between the respective response messages of portable objects, establishing a specific data communication link between the terminal and each portable object transmitting the response message, respectively, and repeating steps (a) through (d);

e) upon the terminal determining of a collision between the response messages of portable objects and not receiving the response message from any of the portable objects, repeating steps (a) through (d); and

wherein the portable object modifies the probability modulation parameter upon receiving one of the marker messages in the absence of any prior response to the call messages as a function of a value of an index that is modified upon receiving one of the marker messages.

12. The method of claim 11, wherein said index is incremented each time a new marker message is received and is reinitialized on receiving a subsequent query message.

13. A method of managing collisions in a system of interchanging data between a plurality of portable objects and a data transceiver terminal suitable for cooperating with portable objects simultaneously present in a communicating range of the terminal, the method comprising the following steps:

a) transmitting call messages from the terminal, at least one of the terminal, the call messages, and the plurality of portable objects including a probability modulation parameter (PMP), the probability modulation parameter corresponding to a probability that at least one of the plurality of portable objects will respond to one of the call messages, wherein the one portable object changes the probability modulation parameter based on whether the one portable object previously responded to one of the call messages transmitted by the terminal;

b) using the PMPs corresponding to those portable objects, determining which ones of the portable objects will respond to the call messages;

c) transmitting a response message from each of the portable objects determined in step (b) to respond to the call messages, each of the response messages including an identifier uniquely identifying the respective portable object transmitting the response message;

d) upon the terminal receiving at least one response message and determining an absence of a collision between the respective response messages of portable objects, establishing a specific data communication link between the terminal and each portable object transmitting the response message, respectively, and repeating steps (a) through (d);

e) upon the terminal determining a collision between the response messages of portable objects and not receiving the response message from any of the portable objects, repeating steps (a) through (d); and

wherein a portable object is capable of being inhibited from sending out a response to the call messages by the portable object receiving a special message sent out by the terminal and containing an identifier corresponding to the portable object, the inhibition being removable upon one of initialization of the portable object and reception of a message.

14. For use in a system for controlling collisions that may occur during interchange of data between a data transceiver terminal and portable objects simultaneously present in a communicating range of the terminal, the terminal comprising:

a transmitter for transmitting call messages from the terminal to the portable object, where at least one of the terminal, the call messages, and the portable objects includes a probability value corresponding to a probability that one of the portable objects will respond to the call messages, the call messages including query messages for initializing the probability value and marker messages for permitting the portable objects to modify the probability value upon receiving the marker messages in an absence of a response to the call messages, wherein the transmitter is configured to transmit the marker messages after the query messages;

a receiver for receiving a response message from each portable object for which it was determined should send a response message based on a corresponding probability value, each response message including an identifier identifying the respective portable object sending the response message;

wherein upon receiving a response message, and in an absence of a collision between response messages of portable objects, the terminal is configured to establish a data communication link between the terminal and one of the portable objects sending the response message, and

wherein upon the terminal determining a collision between the response messages of portable objects and not receiving the response message from one of the portable plurality of objects, the terminal is configured to transmit one or more further call messages.

15. The terminal of claim 14, wherein the terminal is configured to transmit another query message upon detecting a collision.

16.The terminal of claim 15, wherein the terminal is configured to reduce a time interval between two successive call messages in the absence of a response from a portable object within a predetermined period.

16. The terminal of claim 14, wherein the terminal is configured to inhibit a portable object from responding to the call messages by transmitting an inhibit message containing an identifier corresponding to the portable object.