Nuts and Bolts of a Realistic Stochastic Geometric Analysis of mmWave HetNets: Hardware Impairments and Channel Aging

Abstract

Motivated by heterogeneous networks (HetNets) design in improving coverage and by millimeter-wave (mmWave) transmission offering an abundance of extra spectrum, we present a general analytical framework shedding light to the downlink of realistic mmWave HetNets consisting of K tiers of randomly located base stations (BSs). Specifically, we model, by virtue of stochastic geometry tools, the multi-tier multi-user multipleinput multiple-output (MU-MIMO) mmWave network degraded by the inevitable residual additive transceiver hardware impairments (RATHIs) and channel aging. Given this setting, we derive the coverage probability and the area spectral efficiency (ASE), and we subsequently evaluate the impact of residual transceiver hardware impairments (RTHIs) and channel aging on these metrics. Different path-loss laws for line-of-sight (LOS) and nonline-of-sight (NLOS) are accounted for the analysis, which are among the distinguishing features of mmWave systems. Among the findings, we show that the RATHIs have a meaningful impact at the high signal-to-noise ratio (SNR) regime, while the transmit additive distortion degrades further than the receive distortion the system performance. Moreover, serving fewer users proves to be preferable, and the more directive the mmWaves are, the higher the ASE becomes.

Towards the assessment of realistic hybrid precoding in millimeter wave MIMO systems with hardware impairments

“…The additive impairments are modelled as power-dependent Gaussian additive noise [23,27], and results from [27] show that the transmitter distortions have a greater impact than the receive RATHIs. However, in the case of mmWave MIMO systems, only a few works have considered RTHIs in mmWave MIMO systems [31][32][33][34][35]. In [31], the performance of an mmWave system employing analog beamforming under RTHIs is evaluated by using a logarithmic model, which assumes that the combiner losses are only dependent on the number of RF chains.…”

“…However, analog beamforming is not robust for multi‐stream and multi‐user scenarios. In [32], although the major RTHIs are studied, the study is based on orthogonal frequency‐division multiplexing (OFDM) modulation, while in [33] and [34], digital precoding was assumed to obtain the coverage probability in the realistic case of randomly located base stations. Notably, a first attempt to address the impact of HIs was made in [35], where the authors also considered multiplicative phase noise (PN).…”