| 摘要 |
A system for multi-carrier transmission which can secure the transmission capacity under the noise environment whose noise changes cyclically is provided. A mapping section in an ATU-C (ADSL transceiver unit, central office end) memorizes the bit allocation allocating to each carrier and transmission power allocation using for each carrier at the period that the noise generated at the data transmission to a downstream direction is large and the bit allocation allocating to each carrier and transmission power allocation using for each carrier at the period that the noise generated at the data transmission to an upstream direction is large. And a demapping section in an ATU-R (ADSL transceiver unit, remote terminal end) also memorizes the memorized bit allocation and transmission power allocation. At the time of the data transmission to the downstream direction, the bit allocation and transmission power allocation is allocated to each carrier of the high frequency band, by making the bit rate at the period that the noise generated at the data transmission to the downstream direction is small higher than the bit rate at the period that the noise is large. With this, the transmission capacity to the downstream direction can be secured.
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