Theoretical error for asynchronous multi-user large-scale MIMO channel estimation

In this study, the effects of pilot asynchronism on channel estimation of multi-user multiple-input multiple-output systems are analysed. Classical linear sequences such as Gold, Walsh–Hadamard and quaternary were deployed as pilots in large-scale MIMO context aiming to trace their behaviour in asynchronous scenarios. Through this study, it was derived a closed form expression for the channel estimate error, suggesting that asynchronism on channel estimation may introduce deviations from the actual channel and spatial correlation, which decreases the overall performance. Numerical results also demonstrated performance degradation of the single-cell massive MIMO system as asynchronism increases, besides of highlighting the effect of the bit-error-rate floor as the number of base stations antennas increases in such scenarios.