High Beamforming Gain Precoding Weight Design Scheme with Null-Space Expansion for Multiuser Massive MIMO in Time-Varying Channels

Prediction-aided precoding for multiuser massive MIMO null-space expansion

“…The proposed scheme has a smaller degradation of the desired power than NSE, because the proposed weight is designed to follow the time-varying channel as formulated in Eq. (7). Meanwhile, the desired signal power of the NSE-based schemes, including our proposal, is less than ZF-AR since they consume DoFs for extensive null-steering.…”

“…Note that it is not practical to update the weight vector completely continuously in Eq. (7). It is enough to update the weight vector for every symbol duration as long as that is smaller than the channel coherence time.…”

“…(a) Prop. : the proposed scheme, (b) NSE: the conventional NSE, (c) ZF-AR: Zero-Forcing precoding [7] using the prediction channel based on AR model in Eq. (3), (d) ZF: Zero-Forcing precoding (without compensation for time-varying channel impact).…”