Comments on "Symmetric capacity and signal design for L-out-of-K symbol-synchronous CDMA Gaussian channels

For original paper see A. A. Alsugair and R. S. Cheng, ibid., vol. 41, p. 1072-1082 (July, 1995). We show that the signature sequences set that maximizes the lower bound on symmetric capacity derived in the above paper also maximizes the sum capacity of the Gaussian synchronous code-division multiple-access (CDMA) channel. This is done by relying on the equivalence of the eigenvalues of energy-weighted correlation matrices. This result establishes the missing link between the above paper and the sum capacity maximization result by Viswanath et al. (1999).