Patent Document ID: 8238545
Application ID: 12444823
Patent Flag: 1

Claim One:
1. A method performed by a transmitter unit in a multi-tone transmission-based communication system for determining a Power Spectral Density (PSD) of a plurality of users over a physical channel for at least one tone, wherein each of the plurality of users has a minimum required data rate and a maximum allowed power, wherein the method comprises the sequential steps of: a) initializing a weight (w n ) for each user; b) initializing a Lagrange multiplier (μ n ) for each user; c) determining a PSD over the physical channel for at least one tone such that the PSD of all users over the physical channel for said at least one tone minimizes a Lagrangian formulation regarding power, wherein the Lagrangian formulation comprises the weight and the multiplier; d) determining an achieved data rate for each user based on the determined PSD; e) adjusting the Lagrange multiplier of each user; f) without adjusting the weight of each user, iterating steps c) to e) until the achieved data rate of each user is equal to the minimum required data rate of each user respectively; g) only after the achieved data rate of each user is equal to the minimum required data rate of each user, determining the total allocated power of each user; h) adjusting the weight of each user; and i) iterating steps c) to h) until the total allocated power of each user on at least one tone is less than or equal to the maximum allowed power of each user.