Enhanced upstream power back-off: For VDSL lines

Very-high rate Digital Subscriber Lines (VDSL) are beginning to be deployed by competitive network operators. Short lines can radiate high power crosstalk into long lines hence the power transmitted on the short lines should be controlled to limit the degradation they may cause to a competitor´s long lines. This paper presents a new method of enhanced upstream power backoff (eUPBO). eUPBO limits the normalized ensemble of transmit power across lines, unlike previous techniques that operated independently per line. This new technique is effective because it limits the weighted sum crosstalk into any given line, and allows flexible optimizations. This paper shows new algorithms for eUPBO optimizing transmit power per band per user (Level 1), and for eUPBO optimizing transmit spectra per user (Level 2). Simulation results show that the flexibility of eUPBO can significantly increase select users´ bit rates as chosen by the VDSL operator.