| 摘要 |
A sub-rate modulation method that is compatible with full-rate ADSL modems. The method may be used to implement a reduced complexity transceiver, preferably remotely located from the central office or service provider. The method includes instructing the full-rate modem to transmit data using a subset of available carriers; receiving the subset of carriers at the remote location; and performing a reduced complexity time-to-frequency domain transform. The full rate modem is instructed to use every other carrier, resulting in a transmitted time domain sequence that is cyclic-the first half of the symbol is identical to the second half. As a result, the first half of the symbol is treated as an extended cyclic prefix by the sub-rate ADSL modem, resulting in the elimination of the need to perform time-domain equalization at the sub-rate ADSL modem receiver. This substantially reduces the amount of signal processing required by the sub-rate ADSL transceiver. In addition, local echo cancellation need not be performed during the first half of the received symbol period since these values are not utilized in the demodulation process.
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