On Single-Antenna Rayleigh Block-Fading Channels at Finite Blocklength

This paper concerns the maximum coding rate at which data can be transmitted over a noncoherent, singleantenna, Rayleigh block-fading channel using an error-correcting code of a given blocklength with a block-error probability not exceeding a given value. A high-SNR normal approximation of the maximum coding rate is presented that becomes accurate as the signal-to-noise ratio (SNR) and the number of coherence intervals L over which we code tend to infinity. Numerical analyses suggest that the approximation is accurate already at SNR values of 15 dB and when the number of coherence intervals is 10 or more.