Patent ID: 7050489

Claim:
For a very high rate digital subscriber line transmission system having a plurality of modems operating on an access network in which at least some of said modems operate on wires of different lengths and in which there is a target bit rate for each modem, a method of redistributing available bandwidth which includes reducing the transmit power of modems on relatively short wires so that far-end cross talk produced by said modems is reduced, enabling modems on substantially longer wires to transmit at higher bit rates, the method further including producing, in each of at least some of said modems, an energy loading E k for a k th sub-carrier given by: E k = λ ⁢ ⁢ n k F k where n k is the background noise on the k th sub-carrier, F k is a far-end cross talk transfer function for a given wire and λ is a constant, λ being adjusted so that R = ∑ k = 0 N - 1 ⁢ ⁢ log 2 ⁢ ⁢ ( 1 + E k Γ ⁢ ⁢ ( n k + Fext k ) ⁢ ⁢ Γ M ) where Fext k is a far-end cross talk from other very high rate digital subscriber line modems, Γ is a signal to noise ratio-gap, Γ M is a system margin and R is a target bit rate per discrete multitone frame.