Optimal Pilot Placement in Cognitive Radio Systems for Wiener Filtered MMSE Channel Estimation
Boyan Soubachov, Neco Ventura · 2011
intriguing situation for optimal pilot-pattern generation. It has been proposed that in order to attain the lowest possible Mean Squared Error (MSE) of a channel estimator, the pilots should be placed adjacent to an interfering Primary User (PU) to allow for the highest pilot to data symbol cross-correlation and the lowest pilot auto-correlation. In past research, this has been shown to provide a significant decrease in the channel estimator’s MSE; moreover the optimal power loading required such that the PU does not experience interference above a certain threshold from the Secondary User (SU) is not taken into account. This leads to a contradiction between the optimal power loading and the optimal pilot pattern. In this paper, the relationship between these two concepts is investigated with the implementation of a Minimum Mean Squared Error (MMSE) Wiener filter and the optimal pilot positioning is derived. Keywords-OFDM; cognitive radio; MMSE estimation; power loading I.