Costly Power and Symbol Rate Allocation to Sub-Channels for Optimal Real Performance: Water-Filling for Maximal Throughput
The authors analytically allocate to sub-channels costly power and symbol rate to maximize a general throughput function. Link parameters (e.g., modulation order and packet length) are explicitly considered. They provide the structure of the general solution, and for certain scenarios give an explicit solution, which includes the optimal link configuration. A channel can be immediately discarded if its normalized gain is less than the normalized power price. Moreover, when power is "Low", all of it should go to the best sub-channel. In general, the best "M" channels operate at maximal symbol rate, with the SNR that satisfies a single-variable optimizing condition; and at most one additional channel operate at the "Low power" optimum.