Isometric multisignature multiuser MC-CDMA in frequency-selective fading

We characterize the asymptotic spectral efficiency of the linear minimum mean squared error (LMMSE) receiver for multiuser multisignature multicarrier (MC) code-division multiple access (CDMA) communication systems. We consider signatures which are orthogonal at each transmitter. Our results are asymptotic as the number of signatures per user and processing gain both tend to infinity with fixed ratio. Our results rely on approximating covariance matrices with unitarily invariant matrices that are asymptotically free.