we show that the sum mean square error (MSE) of channel estimation (MSE-CE) can be minimized if the UTs’ channel power distributions in the angle-delay domain can be made non-overlapping with proper pilot phase shift scheduling. Taking the time-varying nature of the channel into account, we further investigate channel prediction during the data segment using the received pilot signals. We show that the sum MSE of channel prediction (MSE-CP) can also be minimized if the UTs’ channel power distributions in the angle-delay domain can be made non-overlapping with proper pilot phase shift scheduling, which coincides with the optimal channel estimation condition. A simplified pilot phase shift scheduling algorithm is developed based on this optimal channel acquisition condition. The proposed APSP-CA approach is investigated for cases involving both one symbol and multiple consecutive symbols.

-   The proposed APSP-CA is evaluated in several typical propagation scenarios, and significant performance gains in terms of achievable spectral efficiency over the conventional PSOP-based channel acquisition (PSOP-CA) are demonstrated, especially in high mobility scenarios.

Portions of this work previously appeared in the conference paper [@You15Adjustable].

Notations {#sec:prwb_not}
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We adopt the following notation throughout the paper. We use ${\bar{\jmath}}=\sqrt{-1}$ to denote the imaginary unit. $\left\lfloor x\right\rfloor$ 