| 摘要 |
PROBLEM TO BE SOLVED: To reduce collisions and to shorten the entire processing time by maximizing the number of times of re-transmission for the transmission of a response to a main equipment at the reception of command from the main equipment and repeating it until the transmission succeeds. SOLUTION: A card reader-writer 4 transmits an optional command into a communication area 2 through an antenna 1. In performing first command transmission, the card reader-writer 4 adds the number of times of the re- transmission of the response from respective cards to the command. The number of times of the re-transmission is the maximum number of times capable of re-transmitting the response before receiving the next command when the respective cards fail in response transmission to the card reader-writer 4. The respective cards 3 transmit the response to the card reader-writer 4. At this point, since the probability that the cards 3a and 3b of excellent communication conditions succeed in returning the response to the card reader-writer 4 is high, the card reader-writer 4 attaches acknowledgment(ACK) to the ID and performs the transmission. |
