On the Concavity of the Sum-Rate Function in OFDM Systems

We study the power allocation problem for maximizing the sum rate in orthogonal frequency-division multiplexing systems, where multiple point-to-point links share a set of subcarriers. This problem is hard to solve, in general, due to its nonconvexity. In this letter, we characterize the conditions for the problem to be convex, in which case the problem can be solved efficiently using known algorithms such as gradient projection method. We validate our analysis through simulations.