In coherent systems, when the channel is not known at the receiver, pilot-assisted techniques are needed to estimate the channel. Using OFDM, this paper overcomes the problem of designing such optimum pilot patterns that efficiently estimate doubly selective (in time and frequency)fading channels. We show that,decoupling time- and frequency- selectivity, the challenging process of estimating such channels can be seen as a two-dimensional sampling problem. We further propose efficient sampling patterns depending on the spreading (multipath and Doppler) function of the channel.

Teoría de la Señal y Comunicaciones