Multi-user discrete bit-loading for DMT-based DSL systems

Abstract

This paper investigates the multiuser bit and power allocation problem in discrete multi-tone digital subscriber line modems. A spectrum-management center with knowledge of direct and crosstalk-coupled channel gains allocates the bits and the available power to the subchannels for all users in a common binder. The center uses a multiuser discrete bit-loading algorithm that attempts to minimize the total transmit power given a target sum-rate. This algorithm extends the greedy algorithm for the single-user channel to the multi-user channel. Simulation results for the upstream transmission in very high-speed digital subscriber line show that the total power can be reduced using the multi-user discrete bit-loading algorithm instead of applying. the single-user greedy algorithm iteratively.