PERFECTED PROCESS FOR COLLISION MANAGEMENT IN A DATA EXCHANGE SYSTEM WITHOUT CONTACT.

摘要

The invention relates to a method for controlling collisions in a system of exchanging data between portable objects and at least one sending-receiving terminal capable of cooperating with a series of portable objects that are simultaneously present in the communications field of the terminal. The procedure consists of the following steps: a) the transmission by the terminal of call messages to portable objects; b) the conditional transmission from the portable object to the terminal of a call message response message with a probability possibly less than 100%, wherein the response message contains a specific identification code for the portable object; c) when the terminal receives a response from an identified portable object and if the response does not collide with the response sent by another portable object, a specific data communication link is established between the terminal and the identified portable object, the data is exchanged and the process returns to step a) to perform another iteration; and d) if there is no reception without collision, return to step a) to perform another iteration. According to the invention, the terminal transmissions comprise two types of call messages: interrogation messages, which initialize the probability of response of portable objects and marker messages sent in succession after interrogation messages. Dialer messages are able to instruct portable objects to adjust the probability value when a marker message is received in the absence of a previous response to a call message.