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Massive multiple-input multiple-output (MIMO) networks, where the basestations (BSs) are equipped with large number of antennas and serve a number ofusers simultaneously, are very promising, but suffer from pilot contamination.Despite its importance, delayed channel state information (CSI) due to usermobility, being another degrading factor, lacks investigation in theliterature. Hence, we consider an uplink model, where each BS applieszero-forcing decoder, accounting for both effects, but with the focal point onthe relative users' movement with regard to the BS antennas. In this setting,analytical closed-form expressions for the sum-rate with finite number of BSantennas, and the asymptotic limits with infinite number of BS antennasepitomize the main contributions. In particular, the probability densityfunction of the signal-to-interference-plus-noise ratio and the ergodicsum-rate are derived for any finite number of antennas. Insights of the impactof the arising Doppler shift due to user mobility into the low signal-to-noiseratio regime as well as the outage probability are obtained. Moreover,asymptotic analysis performance results in terms of infinitely increasingnumber of antennas, power, and both numbers of antennas and users (while theirratio is fixed) are provided. The numerical results demonstrate the performanceloss in various Doppler shifts. An interesting observation is that massive MIMOis favorable even in time-varying channel conditions.

Uplink Performance of Conventional and Massive MIMO Cellular Systems with Delayed CSIT