A theoretical framework for capacity-achieving multi-user waterfilling in OFDMA

This paper introduces a theoretical framework for subcarrier and power allocation algorithms in rate-adaptive OFDMA systems. The focal point is locating “capacity-achieving” waterlevels for a given allocation in order to minimize the distance to the boundary of the capacity region. We prove that it is possible to restrict the choice of waterlevels to an optimality polyhedron. This paper introduces weighted subcarrier allocations which have a natural correspondence to this polyhedron, and are therefore promising candidates for the above problem. Based on the introduced theory, a low-complexity algorithm is designed and shown to reliably locate capacity-achieving waterlevels.