Cooperative bit-loading and fairness bandwidth allocation in ADSL systems

This paper examines the performance of bundled ADSL systems and proposes an extension to their bit-loading mechanism that results to fair allocation of the available bandwidth. The “ratemaximization” bit-loading method provides less average data rate compared to the optimum “target-rate” strategy, which depends on the number of active lines in the system and the length of the DSL loop. Under a non-cooperative bit-loading approach, the total data rate is not distributed uniformly among the different active lines. The individual data rate depends on the activation time of each modem relative to the total number of lines in the system. The proposed bit-loading mechanism is applied to the downstream ADSL traffic, is executed by a management unit of the central office, uses the results of the single-user bit-loading mechanism and leads to fair data rate distribution.