Variable bandwidth discrete multi-tone (DMT) rate-adaptive asymmetric digital subscriber line (RADSL) transceiver

摘要

The present invention combines the inherent advantages of half-rate and full-rate DMT modulation schemes. A DMT transceiver of a DSL modem includes a variable bandwidth receiver filter which adjusts the bandwidth of the signal received by a DMT receiver. The variable bandwidth receiver filter may be analog or digital in design. The DMT transceiver further includes an AM radio signal detector and useful bandwidth detector which can detect the presence of AM radio interference (e.g., strong AM radio signals) on the service line. Then, either automatically or with user confirmation, the DMT transceiver adaptively adjusts its bandwidth from, e.g., a full-rate DMT mode to a half-rate DMT mode, or from using all sub-channels to using less than all available sub-channels, by changing the parameters of the variable bandwidth receiver filter, in accordance with the principles of the present invention. A highest number of sub-channel used may be transmitted to a corresponding DMT transceiver at the other end (e.g., at a central office).