Correction to “SDMA With a Sum Feedback Rate Constraint”

This correspondence corrects an error in the proof for theorem, the concavity of the logarithmic function was incorrectly applied to obtain the sum-rate lower bound even though it leads to an upper bound. The revised proof is provided in section II-A, where the aforementioned error has been removed. The changes include replacing the average of a set of signal-to-noise- interference (SINR) terms with an arbitrary term in this set, which allows the use of the concavity of the logarithm function for obtaining a sum-rate lower bound [(5)]. In addition, the proof for the sum-rate upper bound in [1, App. E] has been also modified to replace with a more appropriate one. The modified proof is presented in section II-B.