On capacity of frequency selective multipath channels with path correlations

This paper presents results of ergodic capacity of frequency selective multipath fading channels with path correlations. The exact capacity expression is derived. The main result establishes that, for the uncorrelated case, the ergodic capacity does not depend on either the number of taps or the power delay profile of the channel. However when tap correlation is taken into account, this statement is no longer valid, and high dependence on the channel profile is observed. Although it is impossible to test the impact of different tap correlation models exhaustively, detailed analytical study is carried out under a particular neighbor tap correlation model, i.e., only two neighbor taps are correlated. The worst case that yields the minimal capacity is identified after the intractable and non-convex problem is translated into a convex optimization one. An exact analytical power delay profile for arbitrary number of taps is derived in this case.