Balanced capacity of wireline multiple access channels with individual power constraints

This paper applies the concept of balanced capacity, a fair trade-off between individual and global performance, to the uplink of a Gaussian frequency-selective multiuser channel with K users, where K can be much larger than 2. Individual power constraints are applied to each transmitter, which makes the computation of the balanced capacity very complex. The concept of ´equivalent channel´ is used to derive an explicit expression of the optimal power allocation, that remains compatible with the individual power constraints. The computation of the balanced capacity is then formulated as a set of 2K nonlinear equations. An iterative algorithm providing the exact solution is firstly introduced. A suboptimal solution, based on the Iterative Multiuser Water-Filling (IMWF) algorithm, is then proposed and shown to be very close to the optimal solution. The idea of this alternative method, called ´balanced water-filling´, is to modify the power allocation obtained with the IMWF algorithm in order to get balanced data rates. Results are provided for a wireline access network with 20 users.