CramÉr–Rao Lower Bounds for Subcarrier SNR Estimates Over Multicarrier Channels

Considering orthogonal frequency-division multiplexing transmissions, analytical expressions for the Cramer-Rao lower bounds for the subcarrier signal-to-noise ratio (SNR) estimates are derived. The transmitted signal is assumed to be corrupted by additive white Gaussian noise on the different subcarriers. The channel is assumed to be slowly time-varying over the observation interval, so that it can be assumed constant. It will be shown that the achievable performance on subcarrier SNR estimation can be significantly improved by exploiting the mutual information (the same experienced noise power) between the different tones.