Abstract
Extra-large multiple-input multiple-output (XL-MIMO) systems reveal themselves as a potential candidate for the sixth generation (6G) of wireless communication systems due to their features. As XL-MIMO has a large antenna array, and, typically, the urban environment is plenty of obstacles and reflectors, the spatial non-stationarities are introduced in the signal received at the base station (BS), which means that only a portion of the antenna array is visible to users; hence, accurately modeling XL-MIMO channels is paramount. Previous works on XL-MIMO channel modeling have adopted the non-stationarities only in a spatial sense, and do not consider spatial-time evolution scenarios. Moreover, simplified models with only one set of clusters between the BS and the user equipment (UE) are usually adopted; hence, there is a lack of understanding regarding such channels modeling in the literature. This work proposes and extensively analyzes a double-scattering XL-MIMO channel model, by admitting two types of scattering clusters, one placed at the BS side, and another one located near the UEs. In addition, two distinct antenna array configurations are included in the analysis, the uniform linear and planar arrays (ULA and UPA). We propose a new double-scattering channel model under UPA arrangements, suitable for modeling spatial non-stationarities scenarios in XL-MIMO dynamic environment subject to BS-cluster and UE-cluster correlation, and birth-death channel clusters and scatterers. Numerical results for signal-to-interference-plus-noise ratio (SINR), condition number (CN), and spectral efficiency (SE) performance metrics considering different XL-MIMO channels and system configurations are analyzed via Monte-Carlo simulations, under linear combiners MRC, ZF, and MMSE. Also, we characterize the impact of the number of visible clusters per user, the birth-death rate growth effect on the channel clusters and scatterers, and the favorable propagation effect according to the size of visibility region (VR) overlap. It can be observed that the birth and death processes have a significant impact on the system performance. Under the proposed clustered double-scattering channel modeling, the analyzed XL-MIMO linear receivers presented an SINR degradation around 3 to 4 dB for the MMSE when the number of UEs substantially increased, while the ZF and MRC receivers present a decrease of 1 to 2 dB, approximately, in SINR for the considered dynamic configuration compared with static scenarios.
Highlights
E XTRA-LARGE multiple-input multiple-output (XLMIMO) is a promising research direction of multiantenna technology for the sixth-generation (6G) of wireless communication networks [1]–[3]
NUMERICAL RESULTS we evaluate and validate the proposed XLMIMO channel models considering a) the effects of the number of visible clusters on the pos-combining signal-to-interference-plus-noise ratio (SINR); b) favorable propagation effect and visibility region (VR) overlap; c) The attainable spectral efficiency (SE) in XL-MIMO system equipped with uniform linear array (ULA) and uniform planar array (UPA) received antennas, and d) the effect of birth and death Poisson point processes (PPP) and Poisson clustering process (PCP) over the XL-MIMO performance
The average, minimum, and maximum SINR for the XL-MIMO channel is evaluated by increasing the number of users (K) under three linear receiver schemes (MRC, ZF, and minimum mean-square error (MMSE)) at the base station (BS) equipped with massive ULA antennas
Summary
E XTRA-LARGE multiple-input multiple-output (XLMIMO) is a promising research direction of multiantenna technology for the sixth-generation (6G) of wireless communication networks [1]–[3]. Authors in [16] propose a transformation method to model space-time-variant (STV) two-dimensional non-stationary wideband mMIMO channels considering the disappearance of multipath components (MPCs) and the drift and spread of the time of arrival over the array In this case, only a set of scatterers are implemented with a specific distribution governed by a birth and death process. A clustered double-scattering channel model can reflect more appropriately the effects of the nonstationarity phenomenon in XL arrays, since it depends on both spatial correlations at the communication endpoints, as well as on the scattering structure along the propagation environment Against this background, we emphasize that the works in the literature previously mentioned do not present a specific. U(a, b) is a uniform distribution in [a; b] interval. x ∼ LN (μx, σx) is a random variable x with log-normal distribution, where μx and σx denote the distribution parameters
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