Distributed Adaptive Bit-Loading for Spectrum Optimization in Multi-User Multicarrier Systems

This paper presents a discrete bit-loading algorithm for multi-user multicarrier systems with application to spectrum balancing in digital-subscriber-lines. The algorithm can be implemented in a distributed manner using limited information that is sent to modems by a spectrum management center (SMC). The SMC first classifies users as strong and weak. Strong users then form a rate-penalty table that is used along with the Levin-Campello bit-loading algorithm to limit the interference to weak users. Simulation results show that the proposed algorithm can achieve near-optimal performance. Moreover, the structure of the algorithm enables easy implementation of polite bit and gain adaptation procedures without the need for executing the entire bit-loading algorithm again.