A novel bit and power allocation algorithm for duplex operation of DMT based DSL modems

DMT-based DSL modems allocate power and information bits for quadrature amplitude modulation of discrete tones in each DMT frame. The algorithms in the literature apply only to modems that operate in the simplex mode. This paper describes an algorithm that is suitable for echo cancelled duplex DMT-modems that use overlapping frequency bands for upstream and downstream transmissions. The algorithm minimizes the weighted sum of the power transmitted by the central office (CO) and the customer premise equipment or the remote terminal (RT) with the objective of reducing crosstalk at the CO. The paper also discusses how the algorithm can be used to determine echo canceller performance requirements.