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1. LiDAR-Aided NLoS Path Identification for Enhanced Indoor mmWave Communication

   https://doi.org/10.1109/CCNC54725.2025.10976030  

   Davis, Dalton; Lomboy, Rafaela; Ho, Long Sam; Eltayeb, Mohammed E (January 2025, IEEE)

   IEEE (Ed.)

   Not AvailableThis paper presents a Light Detection and Ranging (LiDAR) based technique for identifying non-line-of-sight (NLoS) communication paths in indoor millimeter-wave (mmWave) environments. This is achieved by using LiDAR distance and backscattered intensity measurements to i) create a map of the communication environment, and ii) identify a set of potential reflective surfaces for NLoS communication. Experimental results demonstrate that the proposed technique, which combines environmental geometry and LiDAR scatter data for ray-tracing, achieves performance comparable to traditional exhaustive search beam training methods, particularly for first-ranked (top- 1) alternative NLoS paths. This offers a promising solution for enhancing indoor mmWave communications in dynamic environments prone to line-of-sight link blockages without the need for a fully dedicated beam training stage. 

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2. Second-Best Beam-Alignment via Bayesian Multi-Armed Bandits

   https://doi.org/10.1109/GLOBECOM38437.2019.9013578  

   Hussain, Muddassar; Michelusi, Nicolo (December 2019, IEEE Global Communications Conference (GLOBECOM))

   Millimeter-wave (mm-wave) systems rely on narrow- beams to cope with the severe signal attenuation in the mm- wave frequency band. However, susceptibility to beam mis- alignment due to mobility or blockage requires the use of beam- alignment schemes, with huge cost in terms of overhead and use of system resources. In this paper, a beam-alignment scheme is proposed based on Bayesian multi-armed bandits, with the goal to maximize the alignment probability and the data-communication throughput. A Bayesian approach is proposed, by considering the state as a posterior distribution over angles of arrival (AoA) and of departure (AoD), given the history of feedback signaling and of beam pairs scanned by the base-station (BS) and the user- end (UE). A simplified sufficient statistic for optimal control is identified, in the form of preference of BS-UE beam pairs. By bounding a value function, the second-best preference policy is formulated, which strikes an optimal balance between exploration and exploitation by selecting the beam pair with the current second-best preference. Through Monte-Carlo simulation with analog beamforming, the superior performance of the second- best preference policy is demonstrated in comparison to existing schemes based on first-best preference, linear Thompson sampling, and upper confidence bounds, with up to 7%, 10% and 30% improvements in alignment probability, respectively. 

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3. Uplink Power Control and SNR-Dependent Beam Alignment Errors in MmWave Cellular Networks

   https://doi.org/10.1109/PIMRC54779.2022.9977460  

   Zia, Muhammad Saad; Blough, Douglas M.; Weitnauer, Mary Ann (January 2022, Proceedings of the IEEE International Symposium on Personal, Indoor and Mobile Radio Communications)

   Beam alignment is a critical aspect in millimeter wave (mm-wave) cellular systems. However, the inherent limitations of channel estimation result in beam alignment errors, which degrade the system performance. For systems with a large number of antennas at the base station, downlink channel estimation is performed using uplink pilot signals. The beam alignment errors, thus, depend on the user equipment (UE) transmit power, which needs to be managed properly as the UEs are battery powered. This paper investigates how the use of uplink power control for the transmission of pilot signals in a mm-wave network affects the downlink beam alignment errors, which depend on various link parameters. We use stochastic geometry and statistics of the Student's t -distribution to develop an analytical model, which captures the interplay between the uplink power control and downlink signal-to-noise ratio (SNR) coverage probability. Our results indicate that using uplink power control significantly reduces UE power consumption without adversely affecting the downlink SNR coverage. 

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4. 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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5. Improving free-space optical communication with adaptive optics for higher order modulation

   https://doi.org/10.1117/12.2568713  

   Nafria, Vijay; Han, Xiao; Djordjevic, Ivan (August 2020, Proceedings Volume 11509, Optics and Photonics for Information Processing XIV)

   Iftekharuddin, Khan M.; Awwal, Abdul A.; Márquez, Andrés; Diaz-Ramirez, Victor H. (Ed.)

   One of the biggest challenges of free-space optical (FSO) communication is the wave-front aberration due to atmospheric turbulence. In FSO links the wave-front distortion manifests as a significant drop in received power, beam wander, information loss, and scintillation effects. The performance of FSO communication system is degraded significantly by the atmospheric turbulence effects. Fortunately, the adaptive optics system offers potential to mitigate the performance degradation, which is relevant for quantum communication applications as well. In our FSO experiment, we perform the transmission of 6.25 GBd QPSK signal over an FSO link without and with adaptive optics, operating at 1550nm. We emulate the atmospheric aberration in our indoor experimental setup by applying random Kolmogorov phase screens on spatial light modulators (SLMs). We demonstrate significant improvements in the power-collected, signal-to-noise-ratio (SNR), and bit-error-rate (BER) performance due to the application of adaptive optics. 

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