Bandwidth scaling for fading channels

The issue of bandwidth scaling has always caused some confusion for channels subject to additive white Gaussian noise plus multipath fading. On the one hand, there is an old result saying that the capacity of the channel (under a power constraint but no bandwidth constraint) is the same as the infinite bandwidth capacity of the non-fading additive noise channel with the same average received power as the fading channel. On the other hand, it appears intuitively that when a CDMA system is spread too widely in bandwidth, it becomes increasingly difficult for a RAKE receiver to measure the channel and correspondingly difficult for detection to take place. Here the authors look at a particularly simple model of the fading channel, but the methodology appears to be extendable to more general models