Duality bounds on the cut-off rate with applications to Ricean fading

We propose to use an expression of Csiszar & Korner´s to upper bound Gallager´s E₀(ρ,Q,r) function. We demonstrate this approach by computing the high SNR asymptotic expansion of the computational cut-off rate of the peak-or average-power limited discrete-time memoryless Ricean fading channel with no-or with only partial-side information at the receiver.