Multiuser Discrete Bit-loading for Digital Subscriber Lines

This paper proposes an efficient algorithm that produces near-optimal discrete bit-loading for a Gaussian interference channel that models a DSL network. It first takes a continuous bit-loading initialization, and then rounds one user´s bits in each tone independently, with rounding direction determined by evaluating a weighted sum rate objective function. After adjusting all the tones of a user, that user´s power constraint is met by a power tightening procedure; then, the algorithm moves to the next user. Convergence of the proposed algorithm is proved. This algorithm can be made distributed by only allowing rounding DOWN the bits, and it can be also applied to Gaussian Multiple Access Channel (MAC) and Gaussian Broadcast Channel (BC) with slight modifications.