| 摘要 |
PROBLEM TO BE SOLVED: To conduct data communication between mobile sets efficiently depending on a state of lines. SOLUTION: Modulation circuits 13, 23 and demodulation circuits 14, 24 of mobile sets 100, 200 cope with a plurality of modulation systems with different information communication speeds. In the case of sending a transmission request at start of data communication to a receiver side, a known pattern of each modulation system is sent together, the receiver side checks an error rate of each modulation system, a modulation system at an information communication speed as fast as possible under a specified error rate is selected and the transmitter side is informed of the selected modulation system. The transmitter side makes data transmission by the informed modulation system to attain efficient transmission in response to the state of lines. Furthermore, when a re-transmission request is received from the receiver side, the re-transmission is made by the modulation system at an information communication speed slower than that of the data transmission to prevent re-transmission from being repeated. |
