| 摘要 |
PURPOSE:To perform error correction coding by an optimum coding rate corresponding to channel conditions and to secure efficient communication by providing a means for grasping the channel conditions and the means for changing the coding rate corresponding to the channel conditions. CONSTITUTION:A reception response packet is received on a transmission side and when a power source is not off, a data transmission operation is ended and reception standby is returned. In the meantime, when an error is detected in a packet received on a reception side, retransmission is requested. Then, on the transmission side, it is judged that the channel conditions are unsatisfactory and the coding rate to be used is lowered. For instance, the coding rate is lowered to 0.73 and 196, 144 codes are used. The data are transmitted to an error correction coder 6 by the unit of 144 bytes, header information such as the data for indicating the coding rate or the like is added to the coded data of 196 bytes and transmission to a channel is performed. In such a manner, by repeating an operation for lowering the coding rate until reaching the prescribed number of times of the retransmission, the use of the coding rate corresponding to the conditions of a radio channel is made possible and transmission efficiency is improved. |
