Gyre Precoding for MU-MIMO Systems

Abstract

This work introduces Gyre Precoding (GP), a novel linear multi-user multiple-input multiple-output (MU-MIMO) precoding approach. GP performs rotations of the symbols of each spatial layer to optimize the precoding performance. To find the rotation angles, we propose a near-optimal, gradient descent-based low-complexity algorithm. GP is constellationagnostic and does not require significant changes to conventional receiver procedures or wireless standards. Computer evaluation results show that GP can achieve 8 dB SNR gains over linear precoding techniques and 2 dB over suboptimal symbol-level precoding (SLP) methods for a 16 × 16 MU-MIMO system. Furthermore, in a 64×12 massive-MIMO scenario in a 5G New Radio (5GNR) setup, GP achieves a 13% higher throughput gain over zero-forcing precoding.

Gyre Precoding and T-Transformation-Based GFDM System for UAV-Aided mMTC Network

“…In the GFDM modulation, the zero padded complex symbols are circularly convolved with the BTRC filter, followed by frequency up conversion [16,26]. The GFDM modulated symbols are power scaled and subsequently precoded with channeldependent multi-user transmit GP schemes [21]. The transmission of the spatially multiplexed precoded signals from the ground BS to the main UAV with ending signal processing operations in the ground segment section of this proposed system.…”

“…The BTRC pulse shaping filter addressed in [21] and used in signal model of Equation ( 5) can be written in the time domain as:…”

“…where (•) T indicates the non-conjugate transpose operator. Considering the GP, a novel linear multiuser multiple-input multiple-output (MU-MIMO) precoding scheme cited at [21], the ZF precoding of matrix size N T × N T can be represented as:…”

“…• T-transformation spreading codes in combination with the walsh Hadamard transform (WHT) and discrete Fourier transform (DFT) is proposed along with recently the introduced gyre precoding (GP) [21] technique. This reduces multi-user interference (MUI) and computational complexity.…”