Maritime channel modeling is crucial for designing robust nearshore communication systems, yet reliable models that account for the dynamic marine environment with varying sea waves, wind conditions, and vessel motions remain scarce. This article investigates land-to-ship maritime wireless channel characteristics at 5.8 GHz based upon an extensive measurement campaign, with concurrent hydrological and meteorological information collection. First, a novel large-scale path loss model with physical foundation and high accuracy is proposed for dynamic marine environments. Then, we introduce the concept of sea-wave-induced fixed-point (SWIFT) fading, a peculiar phenomenon in maritime scenarios that captures the impact of sea surface fluctuations on received power. An enhanced two-ray model incorporating vessel rotational motion is propounded to simulate the SWIFT fading, showing good alignment with measured data, particularly for modest antenna movements. Next, the small-scale fading is studied by leveraging a variety of models including the two-wave with diffuse power (TWDP) and asymmetric Laplace distributions, with the latter performing well in most cases, while TWDP better captures bimodal fading in rough seas. Furthermore, maritime channel sparsity is examined via the Gini index and Rician K factor, and temporal dispersion is characterized. The resulting channel models and parameter characteristics offer valuable insights for maritime wireless system design and deployment.

Ray-tracing (RT) simulators are essential for wireless digital twins, enabling accurate site-specific radio channel prediction for next-generation wireless systems. Yet, RT simulation accuracy is often limited by insufficient measurement data and a lack of systematic validation. This paper presents site-specific location calibration and validation of NYURay, NYU’s in-house ray tracer, at upper mid-band frequencies (6.75 GHz and 16.95 GHz). We propose a location calibration algorithm that corrects GPS-induced position errors by optimizing transmitter-receiver (T-R) locations to align simulated and measured power delay profiles, improving T-R location accuracy by 42.3% for line-of-sight (LOS) and 13.5% for non-line-of-sight (NLOS) scenarios. Validation across 18 T-R locations over distances from 40 to 880 m between transmitter and receiver shows excellent RT accuracy in path loss prediction, with path loss exponent (PLE) deviations under 0.14 when comparing measured versus RT predicted power at all T-R locations. While RT underestimates measured delay spread and angular spreads, their cumulative distributions remain statistically similar. The validated NYURay advances RT validation and provides reliable channel statistics for 6G deployment.

Joint detection and localization of users and scatterers in multipath-rich channels on multiple bands is critical for integrated sensing and communication (ISAC) in 6G. Existing multiband sensing methods are limited by classical beamforming or computationally expensive approaches. This paper introduces alternating direction method of multipliers (ADMM)-assisted compressed multiband sensing (CMS), hereafter referred to as ADMM-CMS, which is a novel framework for multiband sensing using uplink QAM-modulated pilot symbols. To solve the CMS problem, we develop an adaptive ADMM algorithm that adjusts to noise and ensures automatic stopping if converged. ADMM combines the decomposability of dual ascent with the robustness of augmented Lagrangian methods, making it suitable for large-scale structured optimization. Simulations show that ADMM-CMS achieves higher spatial resolution and improved denoising compared to Bartlett-type beamforming, yielding a 34 dB gain in per-antenna transmit power for achieving a 0.9 successful recovery probability (SRP). Moreover, compared to performing compressed sensing separately on the constituent 7 GHz and 10 GHz sub-bands, ADMM-CMS achieves reductions in delay root mean squared error of 35% and 38.1%, respectively, at -41 dBm per-antenna transmit power, while also yielding improved SRP. Our findings demonstrate ADMM-CMS as an efficient enabler of ISAC in frequency range 3 (FR3, 7-24 GHz) for 6G systems.

In this study, we perform a statistical analysis of the radar cross section (RCS) for various test targets in an indoor factory at 25-28 GHz, with the goal of formulating parameters that may be used for target identification and other sensing applications for future wireless systems. The analysis is conducted based on measurements in monostatic and bistatic configurations for bistatic angles of 20^∘, 40^∘, and 60^∘, which are functions of transmitter-receiver (T-R) and target positions, via accurate 3dB beamwidth of 10^∘ in both azimuth and elevation planes. The test targets include unmanned aerial vehicles, an autonomous mobile robot, and a robotic arm. We utilize parametric statistical distributions to fit the measured RCS data. The analysis reveals that the lognormal and gamma distributions are effective in modeling the RCS of the test targets over different reflecting points of the target itself, i.e. when target is in motion. Additionally, we provide a framework for evaluating the deterministic bistatic RCS of a rectangular sheet of laminated wood, due to its widespread use in indoor hotspot environments. Novel deterministic and statistical RCS models are evaluated, incorporating dependencies on the bistatic angle, T-R distance (2m -10m) and the target. The results demonstrate that some proposed RCS models accurately fit the measured data, highlighting their applicability in bistatic configurations.

Site-specific wireless channel simulations via ray tracers can be used to effectively study wireless, decreasing the need for extensive site-specific radio propagation measurements. To ensure that ray tracer simulations faithfully reproduce wireless channels, calibration of simulation results against real-world measurements is required. In this study we introduce NYURay, a 3D ray tracer specifically tailored for mmWave and sub-THz frequencies. To reliably generate site-specific wireless channel parameters, NYURay is calibrated using radio propagation measurements conducted at 28, 73, and 142 GHz in diverse scenarios such as outdoor areas, indoor offices, and factories. Traditional ray tracing calibration assumes angle-dependent reflection, requiring slow iterative optimization techniques with no closed form solution. We propose a simpler and quicker novel calibration method that assumes angle-independent reflection. The effectiveness of the proposed calibration approach is demonstrated using NYURay. When comparing the directional multipath power predicted by NYURay to the actual measured power, the standard deviation in error was less than 3 dB in indoor office environments and less than 2 dB in outdoor and factory environments. The root mean square (RMS) delay spread and angular spread was underpredicted by NYURay due to incomplete environmental maps available for calibration, however an overall agreement between the measured and simulated values was observed. These results highlight the high level of accuracy NYURay provides in generating the site-specific real-world wireless channel, that could be used to generate synthetic data for machine learning.

The exponential rise in energy consumption across wireless communication systems, particularly in anticipation of next-generation wireless systems, necessitates rigorous frameworks for evaluating and optimizing energy efficiency. This paper revisits and expands the concept of the Waste Factor (W), or Waste Figure (WF) in decibel scale, as a unifying metric that captures both utilized and wasted power in cascaded communication systems. Building upon its foundation in system-level power modeling, we integrate the Waste Factor into a refined formulation of the Consumption Factor (CF), the ratio of data rate to total consumed power, linking it directly to Shannon's theoretical limit on energy per bit. This analysis introduces additive energy waste into the classical energy-per-bit derivation through the Waste Factor term. We derive closed-form expressions for energy-per-bit expenditure in both direct and relay-assisted links and develop a decision rule to determine which communication path is more energy efficient under given conditions. While not modeled explicitly, Reflective Intelligent Surfaces (RIS) can be interpreted as a special case of relay-based architectures within this unified formulation, suggesting broader applicability of the Waste Factor framework to emerging 6G use cases. The framework is then extended to a Fixed Wireless Access (FWA) scenario, where uplink and downlink asymmetries, traffic directionality, and component inefficiencies are jointly considered to analyze energy-optimal deployment strategies.

Sixth-generation (6G) networks are poised to revolutionize communication by exploring alternative spectrum options, aiming to capitalize on strengths while mitigating limitations in current fifth-generation (5G) spectrum. This paper explores the potential opportunities and emerging trends for cmWave and sub-THz spectra as key radio enablers. We pose and answer three key questions regarding motivation of additional spectrum to explore the strategic implementation and benefits of cmWave and sub-THz spectra. We also show using case studies how these complementary spectrum bands will enable new applications in 6G, such as integrated sensing and communication (ISAC), holographic surfaces and space-air-ground integrated networks. Numerical simulations reveal that the ISAC performance of cmWave and sub-THz spectra outperforms that of existing 5G spectrum, including sub-6 GHz and mmWave. Additionally, we discuss the importance of these complementary bands over conventional bands to enable extended ultra reliable and low-latency communications with better rate-latency-reliability trade-off. Finally, ongoing standardization endeavours, challenges and promising directions are elucidated for these complementary spectrum bands.

The upper mid-band FR3 spectrum (7-24 GHz) has garnered significant interest for future cellular services. However, utilizing a large portion of this band requires careful interference coordination with incumbent satellite systems. This paper investigates interference from high-power terrestrial base stations (TN-BSs) to satellite downlink receivers. A central challenge is that the victim receivers, i.e., ground-based non-terrestrial user equipment (NTN-UEs) such as satellite customer premises equipment, must first be detected and their channels estimated before the TN-BS can effectively place nulls in their directions. We explore a potential solution where NTN-UEs periodically transmit preambles or beacon signals that TN-BSs can use for detection and channel estimation. The performance of this nulling approach is analyzed in a simplified scenario with a single victim, revealing the interplay between path loss and estimation quality in determining nulling performance. To further validate the method, we conduct a detailed multi-user site-specific ray-tracing (RT) simulation in a rural environment. The results show that the proposed nulling approach is effective under realistic parameters, even with high densities of victim units, although TN-BS may require a substantial number of antennas.

Integrated sensing and communications (ISAC) is emerging as a cornerstone technology for sixth generation (6G) wireless systems, unifying connectivity and environmental mapping through shared hardware, spectrum, and waveforms. The following paper presents an ISAC imaging framework utilizing channel state information (CSI) per-path components, transmitter (TX) positions, and receiver (RX) positions obtained from the calibrated NYURay ray tracer at 6.75 GHz in the upper mid-band. Our work shows how each resolvable multipath component can be extracted from CSI estimation and cast into an equivalent three-dimensional reflection point by fusing its angle and delay information, which is useful and challenging for multi-bounce reflections. The primary contribution of the paper is the two-segment reflection point optimization algorithm, which independently estimates the path lengths from the TX position and RX position to an equivalent reflection point (ERP) on the object surface, thus enabling precise geometric reconstruction. Subsequently, we aggregate the ERPs derived from multiple pairs of TX and RX positions, generating dense three dimensional point clouds representing the objects in the channel. Experimental results validate that the proposed ISAC imaging framework accurately reconstructs object surfaces, edges, and curved features. To the best of our knowledge, this paper provides the first demonstration of multi bounce ISAC imaging using wireless ray tracing at 6.75 GHz.

The vast bandwidth available at millimeter wave (mmWave) and terahertz (THz) frequencies will allow future 6G wireless networks to support ubiquitous and extremely accurate localization and environmental sensing. Prior geometric localization algorithms typically assume single bounce reflections. This paper describes map-assisted positioning with angle and time (MAP-AT), a novel map-based localization algorithm that takes into account multi-bounce reflections, utilizing the angle of arrival and time of flight of multipath signal components to determine the position of a user. The accuracy of MAP-AT is tested against indoor and factory measurement data at mmWave (28 GHz, 60 GHz) and sub-THz (140 GHz) frequencies. Using a single base station as reference, sub-meter accuracy was achieved at mmWave frequencies, and centimeter-level accuracy was achieved at sub-THz frequencies. Accuracy was improved when more base stations were used. Additionally, the performance of sub-Thz signals for sensing objects behind walls is studied by detecting hidden objects behind plywood and drywall in a laboratory environment, with centimeter-level sensing accuracy and identification of hidden objects successfully achieved. This work shows that the high penetration loss of walls and obstructions at sub-THz frequencies poses a challenge to accurate sensing at sub-THz frequencies. Future work is required to sense objects hidden tens of meters behind walls.

This paper presents two innovative four-port probe stations developed by FormFactor Incorporated (FFI) and MPI Corporation (MPI), and a four-port calibration standard design up to 125 GHz for the probe stations. True four-port probing at mmWave and beyond does not yet exist, but is anticipated for future multi-band wireless devices using several antennas and RF chains. The four-port probe stations are housed in the THz measurement facility at NYU and allow simultaneous probing from East, West, North, and South orientations, which presents challenges for calibration. An on-chip Short-Open-Load-Reciprocal (SOLR) calibration (cal) standard is designed leveraging UMC's 28 nm CMOS process. S/O/L standard S-parameters are extracted using a virtual multiline Thru-Reflect-Line (mTRL) cal and used to validate SOLR cal performance via simulations up to 125 GHz. The novel probing solutions from MPI and FFI, along with the SOLR cal, open up considerable opportunities for precise RF characterization across wide frequency ranges.

This paper presents detailed radio propagation measurements for an indoor factory (InF) environment at 6.75 GHz and 16.95 GHz using a 1 GHz bandwidth channel sounder. Conducted at the NYU MakerSpace in the NYU Tandon School of Engineering campus in Brooklyn, NY, USA, our measurement campaign characterizes the radio propagation in a representative small factory with diverse machinery and open workspaces across 12 locations, comprising five line-of-sight (LOS) and seven non-line-of-sight (NLOS) scenarios. Analysis using the close-in (CI) free space path loss (FSPL) model with a 1 m reference distance reveals path loss exponents (PLE) below 2 in LOS at 6.75 GHz and 16.95 GHz, while in NLOS, PLE is similar to free-space propagation (e.g., PLE = 2). The RMS delay spread (DS) decreases at higher frequencies with a clear frequency dependence. Also, measurements show a wider RMS angular spread (AS) in NLOS compared to LOS at both frequency bands, with a decreasing trend as frequency increases. These observations in a dense-scatterer factory environment demonstrate frequency-dependent behavior that differs from existing industry-standard 3GPP models. Our findings provide crucial insights into complex propagation mechanisms in factory environments, essential for designing robust air interface and industrial wireless networks at the upper midband FR3 spectrum.

We develop tractable characterizations of the interference resulting from terrestrial cellular networks radiating towards passive satellite sensing receivers. Such a setting has important implications for the future allocation and terrestrial use of spectrum in the 100 to 300 GHz band. Building on a recently developed stochastic geometry approach, we focus on the outage probability experienced by to a constellation of satellite sensors, which depends upon the distribution of the interference experienced by a typical satellite sensor. The distribution is a function of spatial and temporal randomness. We obtain upper bounds on the outage probability using a large deviation technique for Poisson shot noise, which is a novel adaptation of the Chernoff technique. This analytical method allows for the distribution of the interference to be tightly and tractably bounded. Our analysis theoretically confirms that the satellite sensor's outage probability decreases exponentially as the interference constraint is relaxed, and allows bounding of very low outage probability values, which would be very difficult to simulate.

For the next-generation wireless networks and beyond, both the upper mid-band (7 GHz-24 GHz) and terahertz (100 GHz-1 THz) spectra are gaining global attention from service providers, academic research groups, policy makers, and standards organizations. This article provides an in-depth analysis of recent regulatory rulings and spectrum preferences issued by international standard bodies such as the International Telecommunications Union and Federal Communications Commission as they seek to identify feasible bands for future wireless networks. In this paper, we present the promising spectrum allocations earmarked for 6G and beyond. We also provide exemplars that illuminate the passive service protections and spectrum feasibility for coexistence between terrestrial wireless networks and satellites and other non-terrestrial networks (NTN), and discuss key technical constraints that will challenge future spectrum use for the wireless industry. The findings highlight promising frequency bands while addressing regulatory and technological challenges for future wireless service deployment.

Ray tracing (RT) simulations require accurate transmitter (TX) and receiver (RX) location information from real-world measurements to accurately characterize wireless propagation behavior in an environment. Such wireless propagation measurements typically employ GPS-based logging for TX/RX locations, which can produce meter-level errors that lead to unreliable RT calibration and validation. These location misalignments cause inaccurate interactions between RT-generated multipath components (MPCs) and the modeled 3D environment, which lead to erroneous channel predictions, and severe discrepancies between simulated and measured power delay profiles (PDPs) and channel characteristics. Moreover, the same RT-generated PDPs using inaccurate locations result in calibration errors when adjusting material properties such as conductivity and permittivity. This paper presents a systematic multi-stage TX/RX location calibration framework to correct location errors and consequently align measured and simulated omnidirectional PDPs. Optimization is performed using a computationally efficient multi-stage grid search and the Powell method. Applying the location calibration framework to NYU WIRELESS urban-microcell (UMi) measurements at 6.75 GHz and 16.95 GHz corrected TX/RX location errors of up to 7 m. The framework reduced the composite loss function by 42.3% for line-of-sight (LOS) and 13.5% for non-line-of-sight (NLOS) scenarios. Furthermore, peak power prediction accuracy improved by approximately 1 dB on average. Such improved geometric alignment enables accurate channel prediction, vital for beam management and infrastructure deployment for next-generation wireless networks.

A comprehensive understanding of outdoor urban radio propagation at mmWave and sub-THz frequencies is crucial for enabling novel applications such as wireless cognition, precise position-location, and sensing. This paper summarizes extensive measurements and statistical analysis of outdoor radio propagation data collected in New York City between 2012 and 2021 to formulate a multi-band empirical 3-D statistical channel model (SCM) for outdoor urban open squares and streets. Path loss models and SCMs are derived from over 21000 power delay profiles (PDP) measured in Brooklyn and Manhattan. Analysis of multipath components in PDPs reveal underlying statistical distributions for wireless channel parameters, including number of time-clusters (TC), subpaths in TCs, delays and powers of TCs and subpaths, and spatial-cluster directions. Observations at 142 GHz suggest a sparse channel as subpaths in TCs are exponentially distributed with narrower spread spatial-clusters and higher Ricean K-factor, unlike uniform distributions at 28 and 73 GHz. The proposed SCMs at 142, 73, and 28 GHz extend the open-source NYUSIM channel simulator into sub-THz bands up to 150 GHz. The SCMs can aid in designing modems, antenna arrays, beamforming, and spatial multiplexing approaches, while providing an empirical baseline for propagation simulation and prediction tools, such as ray tracers.

This paper introduces Waste Factor (W) and Waste Figure (WF) to assess power efficiency in any multiple-input multiple-output (MIMO) or single-input multiple-output (SIMO) or multiple-input single-output (MISO) cascaded communication system. This paper builds upon the new theory of Waste Factor, a systematic model for added wasted power in any cascade for parallel systems such as MISO, SIMO, and MIMO, which are prevalent in current wireless networks. Here, we also show the advantage of W compared to conventional metrics for quantifying and analyzing energy efficiency. This work explores the utility of W in assessing energy efficiency in communication channels, within Radio Access Networks (RANs).

Wide bandwidth requirements for multi-Gbps communications have prompted the global telecommunications industry to consider new mid-band spectrum allocations in the 4–8 GHz FR1(C) and 7–24 GHz FR3 bands, above the crowded bands below 6 GHz. Allocations in the lower and upper mid-band aim to balance coverage and capacity, however, there is limited knowledge about the radio propagation characteristics in the 4–24 GHz frequency bands. Here we present the world’s first comprehensive propagation measurement study at 6.75 GHz and 16.95 GHz in mid-band spectrum conducted at the NYU WIRELESS Research Center spanning distances from 11–97 m using 31 dBm EIRP transmit power with 15 and 20 dBi gain rotatable horn antennas at 6.75 GHz and 16.95 GHz, respectively. Analysis of the omnidirectional and directional propagation loss using the close-in free space model with 1 m reference distance reveals a familiar waveguiding effect in indoor environments for line-of-sight (LOS). Compared to mmWave frequencies, the omnidirectional LOS and non-LOS (NLOS) path loss exponents (PLE) are similar, when using a close-in 1m free space path loss reference distance model. Observations of the omnidirectional and directional RMS delay spread (DS) at FR1(C) and FR3 as compared to mmWave and sub-THz frequencies indicate decreasing RMS DS as the carrier frequency is increased. The RMS angular spreads (AS) at 6.75 GHz are found to be wider compared to 16.95 GHz, showing greater number of multipath components from a broader set of directions in the azimuthal spatial plane when compared to higher frequencies. This work also presents results from extensive material penetration loss measurements at 6.75 GHz and 16.95 GHz using co and cross polarized antenna configurations for ten common construction materials found inside buildings and on building perimeters, including concrete walls, low-emissivity glass, wood, doors, drywall, and whiteboard. Our findings show penetration loss increases with frequency for all of the ten materials and partitions tested, and suggest revisions of 3GPP material penetration loss models for at least infrared reflective (IRR) glass and concrete may be necessary. The empirical data and resulting models for radio propagation and penetration presented in this paper provide critical information for future 5G and 6G wireless communications.

This paper presents sub-Terahertz (THz) channel characterization and modeling for an indoor industrial scenario based on radio propagation measurements at 142 GHz in four factories. We selected 82 transmitter-receiver (TX-RX) locations in both line-of-sight (LOS) and non-LOS (NLOS) conditions and collected over 75,000 spatial and temporal channel impulse responses. The TX-RX distance ranged from 5 to 87 m. Steerable directional horn antennas were employed at both link ends and were switched between vertical and horizontal polarization. Measurements were conducted with low RX and high RX antenna heights of 0.5 m and 1.5 m to characterize the propagation channel for close-to-floor applications such as automated guided vehicles. Results show that the low RXs experience an average path loss increase of 10.7 dB and 6.0 dB at LOS and NLOS locations, respectively. In addition, channel enhancement measurements were conducted using a steerable large flat metal plate as a passive reflecting surface, demonstrating omnidirectional path loss reduction from 0.5 to 22 dB with a mean of 6.5 dB. This paper presents the first statistical channel characterization and path loss modeling for industrial scenarios at sub-THz frequencies, highlighting the potential for ultra-broadband factory communications in the 6G era.

The next generation of wireless communication is expected to harness the potential of the sub-THz bands to achieve exceptional performance and ubiquitous connectivity. However, network simulators such as ns-3 currently lack support for channel models above 100 GHz. This limits the ability of researchers to study, design, and evaluate systems operating above 100 GHz. Here, we use the drop-based NYUSIM channel model to simulate channels above 100 GHz in all 3GPP scenarios including urban microcell (UMi), urban macrocell (UMa), rural macrocell (RMa), indoor hotspot (InH), and indoor factory (InF). We evaluate the full stack downlink end-to-end performance (throughput, latency, and packet drop) experienced by a single user equipment (UE) connected to a Next Generation Node B (gNB) operating in the sub-THz bands for three gNB--UE antenna configurations: 8x8--4x4, 16x16--4x4, and 64x64--8x8 by using the NYUSIM channel model at 140 GHz in the ns-3 mmWave module. Our simulations demonstrate that sub-THz bands can enable high-fidelity applications that require data rates exceeding 1 Gbps and latency below 15 milliseconds (ms) using the current mmWave protocol stack, and large antenna arrays. In addition, we show the variation in throughput vs number of realizations and find the optimal number of realizations required to obtain statistically significant results. We strongly encourage researchers worldwide to adopt a similar approach, as it enables the readers to assess the accuracy and reliability of the reported results and enhance the findings' overall interpretability.