Hybrid Beamforming With Reduced RF Chain Based on PZF and PD-NOMA in mmWave Massive MIMO Systems

Abstract

Hybrid beamforming (HB) is a solution for reducing radio frequency (RF) chains in millimeter-wave (mmWave) massive MIMO systems. By reducing RF chains, HB can achieve energy efficient transmission compared to fully digital beamforming of massive MIMO system. However, if the resolution of RF precoder is not quantized, the energy consumption of HB may become similar to fully digital beamforming. And, if the resolution of RF precoder is heavily quantized, the spectral efficiency of HB is decreased significantly. Non-orthogonal multiple access (NOMA) is one of the emerging technologies for the fifth generation (5G) or beyond fifth-generation (B5G) wireless communication to support high spectral efficiency. Especially, power domain NOMA (PD-NOMA) can share same resources to transmit signals and divide the signals in power domain by using successive interference cancellation (SIC). In this paper, the adoption of NOMA shows increase of spectral efficiency in a low-resolution RF precoder. To apply NOMA, two users with high channel correlation are selected according to the proposed criterion. Then, the RF precoder and digital precoder that are applied to both users at the same time are determined. Finally, intra-pair user fairness is achieved by power allocation. The ratio of channel power is compared for each user in each pair. Then, users with high channel power are assigned with low power. It is shown that the spectral efficiency of the proposed scheme is higher than the conventional scheme in heavily quantized RF precoder.INDEX TERMS Millimeter-wave, hybrid beamforming, NOMA, spectral efficiency, precoding.

Energy-Efficient Optimization of mm-Wave Communication Using a Novel Approach of Beamspace MIMO-NOMA

“…Thus, the use of MA-MIMO results in a massive number of RF-Chains, resulting in the drawbacks mentioned earlier. According to previous research, RF-chains share up to 70% of total power consumption at the transmitter and receiver ends [5], or approximately 64W for our proposed scheme with 256 antennas. There are numerous strategies for reducing the RF-Chains' number in order to achieve the required EE while also reducing the system's complexity, such as phase shifter networks [6], complex gain combiners [7], beam selection [8], and antenna selection [9].…”

Hybrid Beamforming for Dual Functioning Multi-input Multi-output Radar using Dimension Reduced-baseband Piecewise Successive Approximation

“…The non-orthogonal multiple access (NOMA) had adopted by Lee et al [20] for the efficient hybrid beamforming in massive MIMO systems. The NOMA was applied by selecting two users with the higher channel correlation, and then RF beamforming and digital beamforming were applied to both users.…”

Robust Hybrid Beam-Forming for Non-Orthogonal Multiple Access in Massive MIMO Downlink

“…In Equation (11), the precoding vectors {f n } N RF n=1 should be cautiously designed to minimize the inter-beam interferences. Due to the NOMA, intra-beam interferences are induced by the power domain multiplexing of users within a beam [33,34]. It can be suppressed by conducting SIC in the order of increasing equivalent channel gains, that is, by performing SIC, the kth user in the nth beam eliminates the interferences from the ith user (∀i > k) in the nth beam.…”