Transform Domain Precoding (TDP) for 5G Evolution and 6G

Due to the availability of wide bandwidth, high frequency band is promising for 5G evolution and 6G. With the increase of antenna ports and bandwidth, existing subband-level precoding consumes high feedback overhead and restricts the precoding granularity. However, channel sparsity can be observed in transformed angular-delay domain in mmWave systems with massive antennas. In this letter, to utilize the sparsity, we propose a transform domain precoding (TDP) to design precoder and feedback. Realistic factors including hybrid beamforming, frequency domain windowing and power allocation are analyzed and evaluated by link-level simulations. Results show that 60%~89% overhead reduction and 2.38%~21% spectrum efficiency (SE) enhancement can be achieved by TDP.

I. Introduction

With the explosive increasing requirement of wireless data rate, high frequency bands, e.g., millimeter wave (mmWave) and terahertz (THz) frequencies, are promising for 5G evolution and 6G due to the large available bandwidth [1]. In 5G new radio (NR), mmWave frequency band between 24.25 GHz and 52.6GHz has been used for wireless transmission [2].