A capacity comparison between time-multiplexed and superimposed pilots

In pilot-based communication systems, a known pilot (training) sequence is transmitted and used for estimation of the unknown channel. Without any strong motivation, recent publications suggest superimposing the pilot to the data instead of time-multiplexing it. In this paper an information theoretic approach is used to compare the communication performances of systems that employ time-multiplexed or superimposed pilots (SIP) for estimation of a frequency-selective blockwise-fading channel. By maximizing a parameterized expression on the mutual information of a SIP-based scheme, we investigate whether SIP-based systems have any gain in performance compared to conventional time-multiplexed systems.