A Downstream Power Back-Off Procedure for Mixed FTTC and FTTDp Scenarios

VDSL2 achieves high bit rates thanks to far-end crosstalk suppression and proper selection of the access network infrastructure. In this paper, we consider one architectural solution, which adopts the standard VDSL2 profile in a Fiber-To-The-Distribution point (FTTDp). During the transition process, FTTDp has to coexist with Fiber-To-The-Cabinet (FTTC) in a mixed VDSL2 scenario. Downstream Power Back-Off (DPBO) for FTTDp is effective to mitigate interference among FTTC and FTTDp. When FTTC terminals are vectored, DPBO leads to reduction of the maximum bit rate for FTTDp as compared to FTTC. In this paper, we propose a modification of the ITU DPBO procedure for FTTC and FTTDp to achieve the same bit rate. The maximum power assigned to FTTDp users is now proportional to the average received power of the vectored FTTC users at the Distribution Point. We obtain the proportionality coefficient, which depends on the number of active FTTC and FTTDp terminals and it is independent of the sub-carrier frequency.