  In many typical mobile communication receivers the channel is estimated based
on pilot symbols to allow for a coherent detection and decoding in a separate
processing step. Currently much work is spent on receivers which break up this
separation, e.g., by enhancing channel estimation based on reliability
information on the data symbols. In the present work, we evaluate the possible
gain of a joint processing of data and pilot symbols in comparison to the case
of a separate processing in the context of stationary Rayleigh flat-fading
channels. Therefore, we discuss the nature of the possible gain of a joint
processing of pilot and data symbols. We show that the additional information
that can be gained by a joint processing is captured in the temporal
correlation of the channel estimation error of the solely pilot based channel
estimation, which is not retrieved by the channel decoder in case of separate
processing. In addition, we derive a new lower bound on the achievable rate for
joint processing of pilot and data symbols.
