Convex-programming bounds on the capacity of flat-fading channels

We propose a technique to derive analytic upper bounds on channel capacity via its dual expression. This is demonstrated on single- and multi-antenna flat fading channels where the receiver has no side information regarding the pathwise realisation of the fading process. The results indicate that the capacity of such channels typically grows double-logarithmically in the SNR and not logarithmically as the piecewise constant fading models predict