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1. Simulating Motion - Incorporating Spatial Consistency into NYUSIM Channel Model

   https://doi.org/10.1109/VTCFall.2018.8690738  

   Ju, Shihao; Rappaport, Theodore S. (August 2018, 2018 IEEE 88th Vehicular Technology Conference (VTC-Fall))

   Abstract: This paper describes an implementation of spatial consistency in the NYUSIM channel simulation platform. NYUSIM is a millimeter wave (mmWave) channel simulator that realizes measurement-based channel models based on a wide range of multipath channel parameters, including realistic multipath time delays and multipath components that arrive at different 3-D angles in space, and generates life-like samples of channel impulse responses (CIRs) that statistically match those measured in the real world. To properly simulate channel impairments and variations for adaptive antenna algorithms or channel state feedback, channel models should implement spatial consistency which ensures correlated channel responses over short time and distance epochs. The ability to incorporate spatial consistency into channel simulators will be essential to explore the ability to train and deploy massive multiple- input and multiple-output (MIMO) and multi-user beamforming in next-generation mobile communication systems. This paper implements spatial consistency in NYUSIM for when a user is moving in a square area with the side length 15 m. The spatial consistency extension will enable NYUSIM to generate realistic evolutions of temporal and spatial characteristics of the wideband CIRs for mobile users in motion, or for multiple users who are in close proximity to one another. 

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2. A Millimeter-Wave Channel Simulator NYUSIM with Spatial Consistency and Human Blockage

   https://doi.org/10.1109/globecom38437.2019.9013273  

   Ju, Shihao; Kanhere, Ojas; Xing, Yunchou; Rappaport, Theodore S. (December 2019, 2019 IEEE Global Communications Conference)

   null (Ed.)

   Abstract—Accurate channel modeling and simulation are indispensable for millimeter-wave wideband communication systems that employ electrically-steerable and narrow beam antenna arrays. Three important channel modeling components, spatial consistency, human blockage, and outdoor-to-indoor penetration loss, were proposed in the 3rd Generation Partnership Project Release 14 for mmWave communication system design. This paper presents NYUSIM 2.0, an improved channel simulator which can simulate spatially consistent channel realizations based on the existing drop-based channel simulator NYUSIM 1.6.1. A geometry-based approach using multiple reflection surfaces is proposed to generate spatially correlated and time-variant channel coefficients. Using results from 73 GHz pedestrian measurements for human blockage, a four-state Markov model has been implemented in NYUSIM to simulate dynamic human blockage shadowing loss. To model the excess path loss due to penetration into buildings, a parabolic model for outdoorto- indoor penetration loss has been adopted from the 5G Channel Modeling special interest group and implemented in NYUSIM 2.0. This paper demonstrates how these new modeling capabilities reproduce realistic data when implemented in Monte Carlo fashion using NYUSIM 2.0, making it a valuable measurement-based channel simulator for fifth-generation and beyond mmWave communication system design and evaluation. Index Terms—5G; mmWave; NYUSIM; channel modeling; channel simulator; spatial consistency; human blockage; outdoor-to-indoor loss; building penetration 

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3. Millimeter Wave and Sub-Terahertz Spatial Statistical Channel Model for an Indoor Office Building

   Shihao Ju, Yunchou Xing (December 2021, IEEE journal on selected areas in communications)

   Abstract—Millimeter-wave (mmWave) and sub-Terahertz (THz) frequencies are expected to play a vital role in 6G wireless systems and beyond due to the vast available bandwidth of many tens of GHz. This paper presents an indoor 3-D spatial statistical channel model for mmWave and sub-THz frequencies based on extensive radio propagation measurements at 28 and 140 GHz conducted in an indoor office environment from 2014 to 2020. Omnidirectional and directional path loss models and channel statistics such as the number of time clusters, cluster delays, and cluster powers were derived from over 15,000 measured power delay profiles. The resulting channel statistics show that the number of time clusters follows a Poisson distribution and the number of subpaths within each cluster follows a composite exponential distribution for both LOS and NLOS environments at 28 and 140 GHz. This paper proposes a unified indoor statistical channel model for mmWave and sub-Terahertz frequencies following the mathematical framework of the previous outdoor NYUSIM channel models. A corresponding indoor channel simulator is developed, which can recreate 3-D omnidirectional, directional, and multiple input multiple output (MIMO) channels for arbitrary mmWave and sub-THz carrier frequency up to 150 GHz, signal bandwidth, and antenna beamwidth. The presented statistical channel model and simulator will guide future air-interface, beamforming, and transceiver designs for 6G and beyond. Index Terms—Millimeter-wave, terahertz, radio propagation, indoor office scenario, channel measurement, channel modeling, channel simulation, NYUSIM, 28 GHz, 140 GHz, 142 GHz, 5G, 6G. 

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4. High Dynamic Range mmWave Massive MU-MIMO with Householder Reflections

   V. Palhares; G. Marti; O. Castañeda; C. Studer (October 2023, Asilomar Conference on Signals, Systems, and Computers)

   All-digital massive multiuser (MU) multiple-input multiple-output (MIMO) at millimeter-wave (mmWave) frequencies is a promising technology for next-generation wireless systems. Low-resolution analog-to-digital converters (ADCs) can be utilized to reduce the power consumption of all-digital basestation (BS) designs. However, simultaneously transmitting user equipments (UEs) with vastly different BS-side receive powers either drown weak UEs in quantization noise or saturate the ADCs. To address this issue, we propose high dynamic range (HDR) MIMO, a new paradigm that enables simultaneous reception of strong and weak UEs with low-resolution ADCs. HDR MIMO combines an adaptive analog spatial transform with digital equalization: The spatial transform focuses strong UEs on a subset of ADCs in order to mitigate quantization and saturation artifacts; digital equalization is then used for data detection. We demonstrate the efficacy of HDR MIMO in a massive MU-MIMO mmWave scenario that uses Householder reflections as spatial transform. 

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5. Resolution-Adaptive All-Digital Spatial Equalization for mmWave Massive MU-MIMO

   https://doi.org/10.1109/SPAWC51858.2021.9593110  

   Castaneda, Oscar; Mirfarshbafan, Seyed Hadi; Ghajari, Shahaboddin; Molnar, Alyosha; Jacobsson, Sven; Durisi, Giuseppe; Studer, Christoph (September 2021, IEEE 22nd International Workshop on Signal Processing Advances in Wireless Communications (SPAWC))

   All-digital basestation (BS) architectures for millimeter-wave (mmWave) massive multi-user multiple-input multiple-output (MU-MIMO), which equip each radio-frequency chain with dedicated data converters, have advantages in spectral efficiency, flexibility, and baseband-processing simplicity over hybrid analog-digital solutions. For all-digital architectures to be competitive with hybrid solutions in terms of power consumption, novel signal-processing methods and baseband architectures are necessary. In this paper, we demonstrate that adapting the resolution of the analog-to-digital converters (ADCs) and spatial equalizer of an all-digital system to the communication scenario (e.g., the number of users, modulation scheme, and propagation conditions) enables orders-of-magnitude power savings for realistic mmWave channels. For example, for a 256-BS-antenna 16-user system supporting 1 GHz bandwidth, a traditional baseline architecture designed for a 64-user worst-case scenario would consume 23 W in 28 nm CMOS for the ADC array and the spatial equalizer, whereas a resolution-adaptive architecture is able to reduce the power consumption by 6.7×. 

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