Analysis of SC-FDMA spectral efficiency over Rayleigh fading channels

Although there are many similarities between SC-FDMA and OFDMA, results presented in literature show that the pre-coding stage in the former worsens the system performance. However, to the best of our knowledge, the reduction of the spectral efficiency has not been quantified yet. Besides, related literature is based mostly on simulations results and there is not an analytical study that validates the conclusions reached through simulations. The purpose of this paper is to perform an analytical study of the spectral efficiency for SC-FDMA when a zero forcing frequency-domain equalizer is applied. Thus, a closed-form expression for the spectral efficiency is provided supposing independence among the frequency channel responses for the allocated sub-carriers. We first show that this expression is a good approximation for interleaved FDMA, and then we analyze its suitability to describe actual ITU channels with a certain coherence bandwidth.