Worst-case expected-rate loss of slow-fading channels

For delay-limited communication over block-fading channels, the difference between the ergodic capacity and the maximum expected rate for coding over a finite number of coherent blocks represents the penalty incurred by the delay constraint. This paper introduces a notion of worst-case expected-rate loss. Focusing on the slow-fading scenario (one block delay), the worst-case expected-rate loss is precisely characterized for the point-to-point fading channel and is characterized to within one bit for the fading-paper channel.