Patent ID: 6690263
Filing Date: 2004-02-10
Classification: G06K

Abstract:
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.