Performance Analysis for Optimal Pilot Spacing in MIMO-OFDM Systems

This paper investigates pilot symbol-assisted channel estimation in multiple-input multiple-output orthogonal frequency division multiplexing systems. Especially, under multipath fading channels, we perform the analysis for optimal pilot spacing that maximizes the effective data rate which represents the number of correctly detected data per unit time. To do this, we first find the statistical properties of the estimated effective channel including interpolation error. After that, utilizing the statistical properties of the estimated effective channel, the average bit error probability and the effective data rate according to the pilot spacing are derived. Furthermore, based on the derived results, we obtain the average optimal pilot spacing to maximize the effective data rate of the systems. In simulation results, we verify analysis for the average bit error probability and effective data rate by comparing analytical and simulation results according to the frequency selectivity of the channel models. The existence of optimal pilot spacing which compromises the average bit error probability and data rate is also confirmed by the analytical results of the effective data rate. Finally, we discuss the relationship between the frequency selectivity of the channels and optimal pilot spacing, and the effectiveness of utilizing average optimal pilot spacing in practical channel models. Simulation results show that, regardless of the frequency selectivity of the channels, the average optimal spacing can achieve at least 93% of maximum effective data rate performance except for the case of the bottom 5%.