Communicating With Extremely Large-Scale Array/Surface: Unified Modeling and Performance Analysis

By Haiquan Lu, Yong Zeng. IEEE Transactions on Wireless Communications, 2021

319 citations recorded by the source corpus.

Wireless communications with extremely large-scale array (XL-array) correspond to systems whose antenna sizes are so large that conventional modeling assumptions, such as uniform plane wave (UPW) impingement, are no longer valid. This paper studies the mathematical modeling and performance analysis of XL-array communications. By deviating from the conventional modeling approach that treats the array elements as sizeless points, we explicitly model their physical area/aperture, which enables a unified modeling for the classical discrete antenna arrays and the emerging active continuous surfaces. As such, a generic array/surface model that accurately takes into account the variations of signal phase, amplitude and projected aperture across array elements is proposed. Based on the proposed model, a closed-form expression of the resulting signal-to-noise ratio (SNR) with the optimal single-user maximum ratio combining/transmission (MRC/MRT) beamforming is derived. The expression reveals that instead of scaling linearly with the antenna number $M$ as in conventional UPW modeling, the SNR with the more generic model increases with $M$ with diminishing return, which is governed by the collective properties of the array, such as the array occupation ratio and the physical sizes of the array along each dimension, while irrespective of the properties of the individual array element. In addition, we have derived an alternative insightful expression for the optimal SNR in terms of the vertical and horizontal angular spans, which are fully determined by the geometric angles formed by the array/surface and user location. Furthermore, we also show that our derived results include the far-field UPW modeling as a special case. One important finding during the study of far-field approximation is the necessity to introduce a new distance criterion to complement the classical Rayleigh distance, termed uniform-power distance (UPD), which concerns the signal amplitude/power variations across array elements, instead of phase variations as for Rayleigh distance. Extensive numerical results are provided to demonstrate the necessity of proper modeling for XL-array communications by comparing the proposed model with various benchmark models.

Subfields: Aerospace Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/8754b04236992acdaa58b033db97e6f35ceb03b7

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Citations in the corpus

6G Wireless Communications: From Far-Field Beam Steering to Near-Field Beam Focusing (2022, background): “Thus, in the near-field channel model, the wireless link from each antenna element to the target user has different path gain and phase variations [3].”
Target Sensing With Intelligent Reflecting Surface: Architecture and Performance (2022, background): “We assume the element-wise channel is in the far field from the IRS controller to IRS elements, while the results can be extended to the case of near-field channel condition when the IRS controller is placed extremely close to IRS elements [38], [39].”
A Tutorial on Extremely Large-Scale MIMO for 6G: Fundamentals, Signal Processing, and Applications (2023, methodology): “The authors in [119] investigated the XL-MIMO system operated in the THz band with 300 GHz carrier frequency.”
A Tutorial on Near-Field XL-MIMO Communications Toward 6G (2023, unknown): “Moreover, the impacts of polarization mismatch and spatial-wideband effect are other factors to consider for accurate near-ﬁeld modelling.”
Holographic MIMO Communications: Theoretical Foundations, Enabling Technologies, and Future Directions (2022, methodology): “The study was later extended to a modular ULA system in [189], and to an UPA system in [190] with a suggested unified modeling for discrete antenna array and continuous surface.”
A Tutorial on Environment-Aware Communications via Channel Knowledge Map for 6G (2023, background): “For example, by dramatically increasing the array size beyond massive MIMO, extremely large-scale MIMO (XL-MIMO) [15]–[18] or extremely large-scale aperture array (ELAA) [13] is expected to achieve super spatial resolution, beamforming gain, and ultra-high spectral efficiency.”
Near-Field Communications: A Tutorial Review (2023, methodology): “Then, the power gain due to the effective antenna aperture is given as follows [39]:”