Fast Near-Field Beam Training for Extremely Large-Scale Array

Wang²,

et al. 2023

IEEE Commun. Lett.

Extremely large-scale Array (ELAA) promises to deliver ultra-high data rates with more antenna elements. Meanwhile, the increase of antenna elements leads to a wider realm of near-field, which challenges the traditional design of codebooks. In this paper, we propose novel codebook design schemes which provide better quantized correlation with limited overhead. First, we analyze the correlation between codewords and channel vectors uniform linear array (ULA) and uniform planar array (UPA). The correlation formula for the ULA channel can be expressed as an elliptic function, and the correlation formula for the UPA channel can be represented as an ellipsoid formula. Based on the analysis, we design a uniform sampling codebook to maximize the minimum quantized correlation and a dislocation ULA codebook to reduce the number of quantized bits further. Besides, we give a better sampling interval for the codebook of the UPA channel. Numerical results demonstrate the appealing advantages of the proposed codebook over existing methods in quantization bit number and quantization accuracy.

“…Remark 2: When the r is sufficiently large, the last 3 terms in (7) can be omitted, and b (r, θ, ϕ) is simplified as…”

Section: B Upa Near-field Channel Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Near-Field Channel Estimation for Extremely Large-Scale Array Communications: A Model-Based Deep Learning Approach

Wang²,

et al. 2023

IEEE Commun. Lett.

IEEE Trans. Veh. Technol.

“…A hierarchical codebook is proposed in [25], whereas, a two-step approach is taken in [26], in which, first, the channel angles are determined using a far-field codebook, and subsequently, distance is determined using a customized polar codebook.…”

Section: B Related Workmentioning

confidence: 99%

“…3) HSPWM: The HSPWM channel of ( 22) can be written using the same matrix form of (26) with some changes. The angles of A R and A T are changed across the channels between the 𝑞 T th Tx SA and 𝑞 R th Rx SA as well as the complex path gains 𝛼 ℓ , ℓ ∈ {1, • • • , 𝐿}.…”

Section: Beamspace Representationmentioning

confidence: 99%

TeraMIMO: A Channel Simulator for Wideband Ultra-Massive MIMO Terahertz Communications

Tarboush

Sarieddeen

Chen

et al. 2021

Following recent advances in terahertz (THz) technology, there is a consensus on the crucial role of THz communications in the next generation of wireless systems. Aiming at catalyzing THz communications research, we propose TeraMIMO, an accurate stochastic MATLAB simulator of statistical THz channels. We simulate ultra-massive multiple-input multipleoutput antenna configurations as critical infrastructure enablers that overcome the limitation in THz communications distances. We consider both line-of-sight and multipath components and propose frequency-and delay-domain implementations for singleand multi-carrier paradigms in both time-invariant and timevariant scenarios. We implement exhaustive molecular absorption computations based on radiative transfer theory alongside alternative sub-THz approximations. We further model THz-specific constraints, including wideband beam split effects, spherical wave propagation, and misalignment fading. We verify TeraMIMO by analogy with measurement-based channel models in the literature and ergodic capacity analysis. We introduce a graphical user interface and a guide for using TeraMIMO in THz channel generation and analyses.

“…However, this method incurs prohibitively high beam training overhead and hence leaving less time for data transmission. To reduce the training overhead, an efficient two-phase beam training method was proposed in [16] that first estimates the spatial angle and then determines the user distance. This method relies on a key fact that the true user spatial angle approximately lies in the middle of a dominant angular region with sufficiently high received signal powers when using far-field DFT beams for beam training.…”

Section: Introductionmentioning

confidence: 99%

6G Wireless Communications: From Far-Field Beam Steering to Near-Field Beam Focusing

et al. 2023

Extremely large-scale array (XL-array) has emerged as a promising technology to enhance the spectrum efficiency and spatial resolution in future wireless networks by exploiting massive number of antennas for generating pencil-like beamforming. This also leads to a fundamental paradigm shift from conventional far-field communications towards the new nearfield communications. In contrast to the existing works that mostly considered simultaneous wireless information and power transfer (SWIPT) in the far field, we consider in this paper a new and practical scenario, called mixed near-and far-field SWIPT, where energy harvesting (EH) and information decoding (ID) receivers are located in the near-and far-field regions of the XL-array base station (BS), respectively. Specifically, we formulate an optimization problem to maximize the weighted sum-power harvested at all EH receivers by jointly designing the BS beam scheduling and power allocation, under the constraints on the maximum sum-rate and BS transmit power. First, for the general case with multiple EH and ID receivers, we propose an efficient algorithm to obtain a suboptimal solution by utilizing the binary variable elimination and successive convex approximation methods. To obtain useful insights, we then study the joint design for special cases. In particular, we show that when there are multiple EH receivers and one ID receiver, in most cases, the optimal design is allocating a portion of power to the ID receiver for satisfying the rate constraint, while the remaining power is allocated to one EH receiver with the highest EH capability. This is in sharp contrast to the conventional far-field SWIPT case, for which all powers should be allocated to ID receivers. Numerical results show that our proposed joint design significantly outperforms other benchmark schemes without the optimization of beam scheduling and/or power allocation.Index Terms-Simultaneous wireless information and power transfer (SWIPT), extremely large-scale array (XL-array), mixed near-and far-field channels, beam scheduling, power allocation.