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.

Extensive work has been carried out in the past year by various organizations in an effort to determine standardized statistical channel impulse response (CIR) parameters for the newly-released FR3 mid-band spectrum ($7.25 \text{GHz}-24.25 \text{GHz}$) [1]–[5]. In this work, we show that the wireless community currently lacks a unified method for presenting key parameters required for transparency and utilization by several constituencies when presenting propagation data for use by standard bodies or third parties to create statistical CIR models. This paper aims to solve the existing problem by offering a standard method to provide key propagation parameters in a point-data format that supports both statistical and site-specific channel characterization. The proposed method offers tremendous promise when data contributors use the minimum agreed-upon measurement and processing specifications such as bandwidth, antenna beamwidth, and noise threshold level. As shown here, the point-data format enables multiple contributors to create channel model standards or pool measurement data to create larger datasets for exploring ray-tracing (e.g. site-specific) channel modeling or training in AI/ML propagation work, and to ensure the most accurate model using a larger dataset that is continually expanded through measurement contributions. The point-data approach includes sitespecific point-by-point propagation data while readily supporting the creation of commonly-used cumulative distribution function (CDF) plot. The indoor hotspot (InH) datasets collected in Spring 2024 at 6.75 GHz and 16.95 GHZ by NYU WIRELESS [1]–[3] are provided for the first time in point-data form, to augment statistical models previously presented solely as CDFs, in order to demonstrate how a standardized approach to measurement data could allow others to utilize the site-specific locations and key channel parameters observed at each location, to better understand, vet, and build upon statistical or site-specific CIRs from the contributions of many different data sources.

Global allocations in the upper mid-band spectrum (4-24 GHz) necessitate a comprehensive exploration of the propagation behavior to meet the promise of coverage and capacity. This paper presents an extensive Urban Microcell (UMi) outdoor propagation measurement campaign at 6.75 GHz and 16.95 GHz conducted in Downtown Brooklyn, USA, using a 1 GHz bandwidth sliding correlation channel sounder over 40-880 m propagation distance, encompassing seven Line of Sight (LOS) and 13 Non-Line of Sight (NLOS) locations. Analysis of the path loss (PL) reveals lower directional and omnidirectional PL exponents compared to mmWave and sub-THz frequencies in the UMi environment, using the close-in (CI) free space PL (FSPL) model with a 1 m reference distance. Additionally, a decreasing trend in root mean square (RMS) delay spread (DS) and angular spread (AS) with increasing frequency was observed. The measured NLOS RMS DS and RMS AS mean values (as computed by 3GPP methods) are found to be consistently lower compared to 3GPP model predictions. Point-data tables with corresponding site-specific environmental information for all measured statistics at each TX-RX location are provided to support the models and results. The spatio-temporal statistics presented here offer valuable insights for the design of nextgeneration wireless systems and networks.

This paper presents detailed radio propagation measurements for an indoor factory (InF) environment at$\mathbf{6. 7 5 ~ G H z}$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 densescatterer 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 mid-band FR3 spectrum.

We present detailed multipath propagation spatial statistics for next-generation wireless systems operating at lower and upper mid-band frequencies spanning 6–24 GHz. The large-scale spatial characteristics of the wireless channel include Az-imuth angular Spread of Departure (ASD) and Zenith angular Spread of Departure (ZSD) of multipath components (MPC) from a transmitter and the Azimuth angular Spread of Arrival (ASA) and Zenith angular Spread of Arrival (ZSA) at a receiver. The angular statistics calculated from measurements were compared with industry-standard 3GPP models, and ASD and ASA values were found to be in close agreement at both 6.75 GHz and 16.95 GHz. Measured LOS ASD was found larger than 3GPP ASD indicating more diverse MPC departure directions in the azimuth. ZSA and ZSD were observed smaller than the 3GPP modeling results as most multipath arrivals and departures during measurements were recorded at the boresight antenna elevation. The wide angular spreads indicate a multipath-rich spatial propagation at 6.75 GHz and 16.95 GHz, showing greater promise for the implementation of MIMO beamforming systems in the mid-band spectrum.

For decades, the terahertz (THz) frequency band had been primarily explored in the context of radar, imaging, and spectroscopy, where multi-gigahertz (GHz) and even THz-wide channels and the properties of THz photons offered attractive target accuracy, resolution, and classification capabilities. Meanwhile, the exploitation of the THz band for wireless communication had originally been limited due to several reasons:1) no immediate need for such high data rates available via THz bands and 2) challenges in designing sufficiently high-power THz systems at reasonable cost and efficiency, leading to what was often referred to as “the THz gap.” Over the recent decade, advances on many fronts have drastically changed the THz landscape. First, the evolution from 5G-to 6G-grade wireless systems dictates the need to support novel bandwidth-hungry applications and services for both data transfer i.e., eXtended Reality (XR), the Metaverse, and vast modeling needs of artificial intelligence (AI) and machine learning (ML), as well as centimeter-precision sensing and classification (i.e., for standalone position location, vehicle-to-everything (V2X), or unmanned aerial vehicle (UAV) tracking). Second, substantial progress in THz hardware has been achieved, offering promise that the THz technology gap will be closed. Hence, THz-band wireless communication seems inevitably an essential part of the future networking technology landscape in the coming decades. To design efficient THz systems, the peculiarities of THz hardware and THz channels need to be understood and accounted for. This roadmap paper first reviews the evolution of the hardware design approaches for THz systems, including electronic, photonic, and plasmonic approaches, and the understanding of the THz channel itself, in diverse scenarios, ranging from common indoors and outdoors scenarios to intrabody and outer space environments. This article then summarizes the lessons learned during this multidecade process and the cutting-edge state-of-the-art findings, including novel methods to quantify power efficiency, which will become more important in making design choices. Finally, this article presents the authors’ perspective and insights on how the evolution of THz systems design will continue toward enabling efficient THz communications and sensing solutions as an integral part of next-generation wireless systems.

New spectrum allocations in the 4–8 GHz FR1(C) and 7–24 GHz FR3 mid-band frequency spectrum are being considered for 5G/6G cellular deployments. This paper presents results from the world’s first comprehensive indoor hotspot (InH) propagation measurement campaign at 6.75 GHz and 16.95 GHz in the NYU WIRELESS Research Center using a 1 GHz wideband channel sounder system over distances from 11 to 97 m in line-of-sight (LOS) and non-LOS (NLOS). Analysis of directional and omnidirectional path loss (PL) using the close-in free space 1 m reference distance model shows a familiar waveguiding effect in LOS with an omnidirectional path loss exponent (PLE) of 1.40 at 6.75 GHz and 1.32 at 16.95 GHz. Compared to mmWave frequencies, the directional NLOS PLEs are lower at FR3 and FR1(C), while omnidirectional NLOS PLEs are similar, suggesting better propagation distances at lower frequencies for links with omnidirectional antennas at both ends of the links, but also, importantly, showing that higher gain antennas will offer better coverage at higher frequencies when antenna apertures are kept same over all frequencies. Comparison of the omnidirectional and directional RMS delay spread (DS) at FR1(C) and FR3 with mmWave frequencies indicates a clear decrease with increasing frequency. The mean spatial lobe and omnidirectional RMS angular spread (AS) is found to be wider at 6.75 GHz compared to 16.95 GHz indicating more multipath components are found in the azimuthal spatial domain at lower frequencies.

The 4-8 GHz FR1(C) and 7-24 GHz upper mid-band FR3 spectrum are promising new 6G spectrum allocations being considered by the International Telecommunications Union (ITU) and major governments around the world. There is an urgent need to understand the propagation behavior and radio coverage, outage, and material penetration for the global mobile wireless industry in both indoor and outdoor environments in these emerging frequency bands. This work presents measurements and models that describe the penetration loss in co-polarized and cross-polarized antenna configurations, exhibited by common materials found inside buildings and on building perimeters, including concrete, low-emissivity glass, wood, doors, drywall, and whiteboard at 6.75 GHz and 16.95 GHz. Measurement results show consistent lower penetration loss at 6.75 GHz compared to 16.95 GHz for all ten materials measured for co and cross-polarized antennas at incidence. For instance, the low-emissivity glass wall presents 33.7 dB loss at 6.75 GHz, while presenting 42.3 dB loss at 16.95 GHz. Penetration loss at these frequencies is contrasted with measurements at sub-6 GHz, mmWave and sub-THz frequencies along with 3GPP material penetration loss models. The results provide critical knowledge for future 5G and 6G cellular system deployments as well as refinements for the 3GPP material penetration models.

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).

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 ends and were switched between vertical and horizontal polarization. Measurements were conducted with the low RX and high RX 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 at sub-THz frequencies, highlighting the potential for ultra-broadband factory communications in the 6G era.

Radio channels at mmWave and sub-THz frequencies for 5G and 6G communications offer large channel band-widths (hundreds of MHz to several GHz) to achieve multi-Gbps data rates. Accurate modeling of the radio channel for these wide bandwidths requires capturing the absolute timing of multipath component (MPC) propagation delays with sub-nanosecond accuracy. Achieving such timing accuracy is challenging due to clock drift in untethered transmitter (TX) and receiver (RX) clocks used in time-domain channel sounders, yet will become vital in many future 6G applications. This paper proposes a novel solution utilizing precision time protocol (PTP) and periodic drift correction to achieve absolute timing for MPCs in power delay profiles (PDPs) -captured as discrete samples using sliding correlation channel sounders. Two RaspberryPi computers are programmed to implement PTP over a dedicated Wi-Fi link and synchronize the TX and RX Rubidium clocks continuously every second. This synchronization minimizes clock drift, reducing PDP sample drift to 150 samples/hour, compared to several thousand samples/hour without synchronization. Additionally, a periodic drift correction algorithm is applied to eliminate PDP sample drift and achieve sub-nanosecond timing accuracy for MPC delays. The achieved synchronicity eliminates the need for tedious and sometimes inaccurate ray tracing to synthesize omnidirectional PDPs from directional measurements. The presented solution shows promise in myriad applications, including precise position location and distributed systems that require sub-nanosecond timing accuracy and synchronization among components.

In this paper, we expand upon a new metric called the Waste Factor$(W)$, a mathematical framework used to evaluate power efficiency in cascaded communication systems, by accounting for power wasted in individual components along a cascade. We show that the derivation of the Waste Factor, a unifying metric for defining wasted power along the signal path of any cascade, is similar to the mathematical approach used by H. Friis in 1944 to develop the Noise Factor$(F)$, which has since served as a unifying metric for quantifying additive noise power in a cascade. Furthermore, the mathematical formulation of$W$can be utilized in artificial intelligence (AI) and machine learning (ML) design and control for enhanced power efficiency. We consider the power usage effectiveness (PUE), which is a widely used energy efficiency metric for data centers, to evaluate$w$for the data center as a whole. The use of$W$allows easy comparison of power efficiency between data centers and their components. Our study further explores how insertion loss of components in a cascaded communication system influences$w$at 28 GHz and 142 GHz along with the data rate performance, evaluated using the consumption efficiency factor (CEF). We observe CEF's marked sensitivity, particularly to phase shifter insertion loss changes. Notably, CEF variations are more prominent in uplink transmissions, whereas downlink transmissions offer relative CEF stability. Our exploration also covers the effects of varying User Equipment (UE) and Base Station (BS) deployment density on CEF in cellular networks. This work underscores the enhanced energy efficiency at 142 GHz, compared to 28 GHz, as UE and BS numbers escalate.

In the US, people spend 87% of their time indoors and have an average of four connected devices per person (in 2020). As such, providing indoor coverage has always been a challenge but becomes even more difficult as carrier frequencies increase to mmWave and beyond. This paper investigates the outdoor and outdoor-indoor coverage of an urban network comparing globally standardized building penetration models and implementing models to corresponding scenarios. The glass used in windows of buildings in the grid plays a pivotal role in determining the outdoor-to-indoor propagation loss. For 28 GHz with 1 W/polarization transmit power in the urban street grid, the downlink data rates for 90% of outdoor users are estimated at over 250 Mbps. In contrast, 15% of indoor users are estimated to be in outage, with SNR <−3 dB when base stations are 400 m apart with one-fifth of the buildings imposing high penetration loss (∼ 35 dB). At 3.5 GHz, base stations may achieve over 250 Mbps for 90% indoor users if 400 MHz bandwidth with 100 W/polarization transmit power is available. The methods and models presented can be used to facilitate decisions regarding the density and transmit power required to provide high data rates to majority users in urban centers.

Wide swaths of bandwidth at millimeter-wave (mm- Wave) and Terahertz (THz) frequencies stimulate diverse applications in wireless sensing, imaging, position location, cloud computing, and much more. These emerging applications motivate wireless communications hardware to operate with multi- Gigahertz (GHz) bandwidth, at nominal costs, minimal size, and power consumption. Channel sounding system implementations currently used to study and measure wireless channels utilize numerous commercially available components from multiple manufacturers that result in a complex and large assembly with many costly and fragile cable interconnections between the constituents and commonly achieve a system bandwidth under one GHz. This paper presents an evaluation board (EVB) design that features a sliding correlator based channel sounder with 2 GHz null-to-null RF bandwidth in a single monolithic integrated circuit (IC) fabricated in 65 nm CMOS technology. The EVB landscape provides necessary peripherals for signal interfacing, amplification, buffering, and enables integration into both the transmitter and receiver of a channel sounding system, thereby reducing complexity, size, and cost through integrated design. The channel sounder IC on the EVB is the world's first to report gigabit-per-second baseband operation using low-cost CMOS technology, allowing the global research community to now have an inexpensive and compact channel sounder system with nanosecond time resolution capability for the detection of multipath signals in a wireless channel.