IMPROVEMENTS IN, OR RELATING TO, DIGITAL TRANSMISSION

摘要

The present invention combines the advantages of OFDD with Frequency Divided Duplex (FDD), thus enabling the reach of a vdsl transmission system to be extended. The present invention requires that: the use of an extra cyclic prefix; and for longer lines, the frequencies above the FDD band are not used, in other words. This in turn means that: time-synchronisation is performed between all transmitters in the ONUs and the NTs; timing advance is calculated from the line length; and different sub-carriers are used in up-stream and down-stream directions.