Optimally balancing data and pilot power for adaptive MIMO-OFDM systems

While pilot symbols facilitate channel estimation, they reduce the transmit energy for data symbols per OFDM symbol under a fixed total transmit power constraint. In this paper, we investigate the effect of the pilot-to-data power ratio (PDPR) on multilevel quadrature amplitude modulation (M-QAM) multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with adaptive modulation in order to provide a basic framework for finding the optimal PDPR in current and emerging standards using MIMO-OFDM. In particular, we derive the optimal PDPR in terms of average symbol error rate (SER) and spectral efficiency according to different receiver types such as zero-forcing (ZF) and minimum mean square error (MMSE). Employing the optimal PDPR results in higher spectral efficiency and lower SER without using any additional resource.