Comunicació presentada en la 16th European Wireless Conference 2010 (EW '10), celebrada els dies 12, 13, 14 i 15 d’abril de 2010 a Lucca (Itàlia), organitzada per l’IMT Institute for Advanced Studies.

The optimization of the pilot overhead in wireless fading channels is investigated, and the dependence of this overhead on various system parameters of interest (e.g., fading rate, signal-to-noise ratio) is quantified. The achievable pilot-based spectral efficiency is expanded with respect to the fading rate about the no-fading point, which leads to an accurate order expansion for the pilot overhead. This expansion identifies that the pilot overhead, as well as the spectral efficiency penalty with respect to a reference system with genie-aided CSI (channel state information) at the receiver, depend on the square root of the normalized Doppler frequency. It is also shown that the widely-used/nblock fading model is a special case of more accurate continuous fading models in terms of the achievable pilot-based spectral efficiency. Furthermore, it is established that the overhead optimization for multiantenna systems is effectively the same as for single-antenna systems with the/nnormalized Doppler frequency multiplied by the number of transmit antennas.

This research was supported by the government of Spain through the project TEC2009-13000 and the/nproject CONSOLIDER-INGENIO 2010 CSD2008-00010 ”COMONSENS”.