Showing papers by "Theodore S. Rappaport published in 2019"
TL;DR: This paper offers the first in-depth look at the vast applications of THz wireless products and applications and provides approaches for how to reduce power and increase performance across several problem domains, giving early evidence that THz techniques are compelling and available for future wireless communications.
Abstract: Frequencies from 100 GHz to 3 THz are promising bands for the next generation of wireless communication systems because of the wide swaths of unused and unexplored spectrum. These frequencies also offer the potential for revolutionary applications that will be made possible by new thinking, and advances in devices, circuits, software, signal processing, and systems. This paper describes many of the technical challenges and opportunities for wireless communication and sensing applications above 100 GHz, and presents a number of promising discoveries, novel approaches, and recent results that will aid in the development and implementation of the sixth generation (6G) of wireless networks, and beyond. This paper shows recent regulatory and standard body rulings that are anticipating wireless products and services above 100 GHz and illustrates the viability of wireless cognition, hyper-accurate position location, sensing, and imaging. This paper also presents approaches and results that show how long distance mobile communications will be supported to above 800 GHz since the antenna gains are able to overcome air-induced attenuation, and present methods that reduce the computational complexity and simplify the signal processing used in adaptive antenna arrays, by exploiting the Special Theory of Relativity to create a cone of silence in over-sampled antenna arrays that improve performance for digital phased array antennas. Also, new results that give insights into power efficient beam steering algorithms, and new propagation and partition loss models above 100 GHz are given, and promising imaging, array processing, and position location results are presented. The implementation of spatial consistency at THz frequencies, an important component of channel modeling that considers minute changes and correlations over space, is also discussed. This paper offers the first in-depth look at the vast applications of THz wireless products and applications and provides approaches for how to reduce power and increase performance across several problem domains, giving early evidence that THz techniques are compelling and available for future wireless communications.
1,352 citations
TL;DR: Results show that the coordination can improve network performance by suppressing interference when it exists, and that macrodiversity alone may offer sufficient link and capacity improvement and that CoMP may not be necessary for interference coordination at mmWave when narrow directional beams are used.
Abstract: Millimeter-wave (mmWave) will be used for fifth-generation (5G) wireless systems. While many recent empirical studies have presented propagation characteristics at mmWave bands, macrodiversity and Coordinated Multipoint (CoMP) have not been carefully studied. This paper describes a large-scale mmWave base station diversity measurement campaign at 73 GHz in an urban microcell (UMi) in downtown, Brooklyn, NY, USA, and provides the first detailed analysis of CoMP and macrodiversity performance based on extensive measurements. The research employed nine different base station locations in a 200 m by 200 m area and considered 36 individual transmitter–receiver combinations for extensive co- and cross-polarized varying directional beam channel impulse response measurements. From the measured data, hypothesis testing with cross-validation shows that large-scale shadow fading of directional path loss at an RX from multiple base stations can be modeled as being independent. To consider life-like human blockage in CoMP and macrodiversity analysis, simulated human blockage traces are superimposed on the directional measurements to quantitatively show that a user that is served by multiple base stations undergoes dramatically less outage in the presence of rapid fading events, compared to a single serving base station. Moreover, the base station diversity measurements are used to determine the effectiveness of downlink precoding techniques for mmWave CoMP. While results show that the coordination can improve network performance by suppressing interference when it exists, nearly half of the 680 000 directional CoMP measurements (~43%) result in no interference for either user, meaning that macrodiversity alone may offer sufficient link and capacity improvement and that CoMP may not be necessary for interference coordination at mmWave when narrow directional beams are used.
97 citations
01 Dec 2019
TL;DR: In this paper, the main propagation mechanisms at millimeter wave and Terahertz frequencies at 28, 73, and 140 GHz were analyzed using a wideband sliding correlation based channel sounder system with rotatable narrow-beam horn antennas.
Abstract: This paper provides indoor reflection, scattering, transmission, and large-scale path loss measurements and models, which describe the main propagation mechanisms at millimeter wave and Terahertz frequencies. Channel properties for common building materials (drywall and clear glass) are carefully studied at 28, 73, and 140 GHz using a wideband sliding correlation based channel sounder system with rotatable narrow-beam horn antennas. Reflection coefficient is shown to linearly increase as the incident angle increases, and lower reflection loss (e.g., stronger reflections) are observed as frequencies increase for a given incident angle. Although backscatter from drywall is present at 28, 73, and 140 GHz, smooth surfaces (like drywall) are shown to be modeled as a simple reflected surface, since the scattered power is 20 dB or more below the reflected power over the measured range of frequency and angles. Partition loss tends to increase with frequency, but the amount of loss is material dependent. Both clear glass and drywall are shown to induce a depolarizing effect, which becomes more prominent as frequency increases. Indoor propagation measurements and large-scale indoor path loss models at 140 GHz are provided, revealing similar path loss exponent and shadow fading as observed at 28 and 73 GHz. The measurements and models in this paper can be used for future wireless system design and other applications within buildings for frequencies above 100 GHz.
64 citations
20 May 2019
TL;DR: It is shown that scattering can become a prominent propagation mechanism as frequencies extend to millimeter-wave (mmWave) and beyond, but at other times can be treated like simple reflection.
Abstract: This paper provides an analysis of radio wave scattering for frequencies ranging from the microwave to the Terahertz band (e.g., 1 GHz–1 THz), by studying the scattering power reradiated from various types of materials with different surface roughnesses. First, fundamentals of scattering and reflection are developed and explained for use in wireless mobile radio, and the effect of scattering on the reflection coefficient for rough surfaces is investigated. Received power is derived using two popular scattering models — the directive scattering (DS) model and the radar cross section (RCS) model through simulations over a wide range of frequencies, materials, and orientations for the two models, and measurements confirm the accuracy of the DS model at 140 GHz. This paper shows that scattering can become a prominent propagation mechanism as frequencies extend to millimeter-wave (mmWave) and beyond, but at other times can be treated like simple reflection. Knowledge of scattering effects is critical for appropriate and realistic channel models, which further support the development of massive multiple input-multiple output (MIMO) techniques, localization, ray tracing tool design, and imaging for future 5G and 6G wireless systems.
64 citations
01 Dec 2019
TL;DR: In this paper, a geometry-based approach using multiple reflection surfaces is proposed to generate spatially correlated and time-variant channel coefficients for mmWave wideband communication systems that employ electrically steerable and narrow beam antenna arrays.
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 outdoor-to-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.
55 citations
Posted Content•
TL;DR: Indoor propagation measurements and large-scale indoor path loss models at 140 GHz are provided, revealing similar path loss exponent and shadow fading as observed at 28 and 73 GHz.
Abstract: This paper provides indoor reflection, scattering, transmission, and large-scale path loss measurements and models, which describe the main propagation mechanisms at millimeter wave and Terahertz frequencies. Channel properties for common building materials (drywall and clear glass) are carefully studied at 28, 73, and 140 GHz using a wideband sliding correlation based channel sounder system with rotatable narrow-beam horn antennas. Reflection coefficient is shown to linearly increase as the incident angle increases, and lower reflection loss (e.g., stronger reflections) are observed as frequencies increase for a given incident angle. Although backscatter from drywall is present at 28, 73, and 140 GHz, smooth surfaces (like drywall) are shown to be modeled as a simple reflected surface, since the scattered power is 20 dB or more below the reflected power over the measured range of frequency and angles. Partition loss tends to increase with frequency, but the amount of loss is material dependent. Both clear glass and drywall are shown to induce a depolarizing effect, which becomes more prominent as frequency increases. Indoor propagation measurements and large-scale indoor path loss models at 140 GHz are provided, revealing similar path loss exponent and shadow fading as observed at 28 and 73 GHz. The measurements and models in this paper can be used for future wireless system design and other applications within buildings for frequencies above 100 GHz.
45 citations
TL;DR: Adaptive tuning for varying atmospheric absorption meets the military requirements for quickly adjusting covert communication zones to accommodate potentially rapid movements of network nodes, dynamic output power constraints, and changing environmental conditions.
Abstract: Military communications networks can leverage much of the millimeter-wave (mm-wave) technology being investigated and developed for 5G cellular but require special attention to the unique military requirements. This paper highlights the special communications' requirements of specific military local area networks and discusses how higher band mm-wave technology can contribute to high data rates and simultaneously achieve covertness. Adaptive tuning for varying atmospheric absorption meets the military requirements for quickly adjusting covert communication zones to accommodate potentially rapid movements of network nodes, dynamic output power constraints, and changing environmental conditions.
39 citations
01 Dec 2019
TL;DR: This work develops an accurate 3-D ray tracer for an indoor office environment and shows how increasing the number of base stations improves the average non-line-of-sight position location accuracy to 5.5 cm at 21 locations with a maximum propagation distance of 24.5 m.
Abstract: Accurate precise positioning at millimeter wave frequencies is possible due to the large available bandwidth that permits precise on-the-fly time of flight measurements using conventional air interface standards. In addition, narrow antenna beamwidths may be used to determine the angles of arrival and departure of the multipath components between the base station and mobile users. By combining accurate temporal and angular information of multipath components with a 3-D map of the environment (that may be built by each user or downloaded a-priori), robust localization is possible, even in non-line-of-sight environments. In this work, we develop an accurate 3-D ray tracer for an indoor office environment and demonstrate how the fusion of angle of departure and time of flight information in concert with a 3-D map of a typical large office environment provides a mean accuracy of 12.6 cm in line-of- sight and 16.3 cm in non-line-of-sight, over 100 receiver distances ranging from 1.5 m to 24.5 m using a single base station. We show how increasing the number of base stations improves the average non-line-of-sight position location accuracy to 5.5 cm at 21 locations with a maximum propagation distance of 24.5 m.
35 citations
Posted Content•
TL;DR: NYUSIM 2.0 is presented, an improved channel simulator which can simulate spatially consistent channel realizations based on the existing drop-based channel simulator NYUSIM 1.6.1, making it a valuable measurement- based channel simulator for fifth-generation and beyond mmWave communication system design and evaluation.
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 outdoor-to-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.
29 citations
Posted Content•
TL;DR: In this article, the authors provide an analysis of radio wave scattering for frequencies ranging from the microwave to the Terahertz band (e.g., 1 GHz - 1 THz), by studying the scattering power reradiated from various types of materials with different surface roughness.
Abstract: This paper provides an analysis of radio wave scattering for frequencies ranging from the microwave to the Terahertz band (e.g., 1 GHz - 1 THz), by studying the scattering power reradiated from various types of materials with different surface roughnesses. First, fundamentals of scattering and reflection are developed and explained for use in wireless mobile radio, and the effect of scattering on the reflection coefficient for rough surfaces is investigated. Received power is derived using two popular scattering models - the directive scattering (DS) model and the radar cross section (RCS) model through simulations over a wide range of frequencies, materials, and orientations for the two models, and measurements confirm the accuracy of the DS model at 140 GHz. This paper shows that scattering can become a prominent propagation mechanism as frequencies extend to millimeter-wave (mmWave) and beyond, but at other times can be treated like simple reflection. Knowledge of scattering effects is critical for appropriate and realistic channel models, which further support the development of massive multiple input-multiple output (MIMO) techniques, localization, ray tracing tool design, and imaging for future 5G and 6G wireless systems.
27 citations
20 Nov 2019
TL;DR: In this article, the authors proposed a fully-digital direct-conversion array receiver at 28 GHz. The design consists of a custom 28 GHz patch antenna sub-array providing gain in the elevation plane, with azimuthal plane beamforming provided by real-time digital signal processing (DSP) algorithms running on a Xilinx Radio Frequency System on Chip (RF SoC).
Abstract: This paper discusses early results associated with a fully-digital direct-conversion array receiver at 28 GHz. The proposed receiver makes use of commercial off-the-shelf (COTS) electronics, including the receiver chain. The design consists of a custom 28 GHz patch antenna sub-array providing gain in the elevation plane, with azimuthal plane beamforming provided by real-time digital signal processing (DSP) algorithms running on a Xilinx Radio Frequency System on Chip (RF SoC). The proposed array receiver employs element-wise fully-digital array processing that supports ADC sample rates up to 2 GS/second and up to 1 GHz of operating bandwidth per antenna. The RF mixed-signal data conversion circuits and DSP algorithms operate on a single-chip RFSoC solution installed on the Xilinx ZCU1275 prototyping platform.
Posted Content•
TL;DR: In this paper, an accurate 3D ray tracer for an indoor office environment and demonstrate how the fusion of angle of departure and time of flight information in concert with a 3-D map of a typical large office environment provides a mean accuracy of 12.6 cm in line-of-sight and 16.3 cm in non-line of sight, over 100 receiver distances ranging from 1.5 m to 24.5 cm using a single base station.
Abstract: Accurate precise positioning at millimeter wave frequencies is possible due to the large available bandwidth that permits precise on-the-fly time of flight measurements using conventional air interface standards. In addition, narrow antenna beamwidths may be used to determine the angles of arrival and departure of the multipath components between the base station and mobile users. By combining accurate temporal and angular information of multipath components with a 3-D map of the environment (that may be built by each user or downloaded a-priori), robust localization is possible, even in non-line-of-sight environments. In this work, we develop an accurate 3-D ray tracer for an indoor office environment and demonstrate how the fusion of angle of departure and time of flight information in concert with a 3-D map of a typical large office environment provides a mean accuracy of 12.6 cm in line-of-sight and 16.3 cm in non-line-of-sight, over 100 receiver distances ranging from 1.5 m to 24.5 m using a single base station. We show how increasing the number of base stations improves the average non-line-of-sight position location accuracy to 5.5 cm at 21 locations with a maximum propagation distance of 24.5 m.
26 May 2019
TL;DR: In this paper, a programmable ultra-wideband sliding correlator-based channel sounder with high temporal and spatial resolution is designed in standard 65 nm CMOS, which can be configured either as a baseband transmitter to generate a pseudo-random spread spectrum signal with flexible sequence lengths, or as a receiver having an absolute timing reference to obtain power delay profiles of the multipath components of the wireless channel.
Abstract: A programmable ultra-wideband sliding correlator-based channel sounder with high temporal and spatial resolution is designed in standard 65 nm CMOS. The baseband chip can be configured either as a baseband transmitter to generate a pseudo-random spread spectrum signal with flexible sequence lengths, or as a baseband receiver with sliding correlator having an absolute timing reference to obtain power delay profiles of the multipath components of the wireless channel. The sequence achieved a chip rate of one Giga-bit-per-second, resulting in a multipath delay resolution of 1 ns. The baseband chip occupies an area of 0.66 mm × 1 mm with a power dissipation of 6 mA at 1.1 V in 65 nm CMOS. The sliding correlator-based channel sounder in this work is a critical block for future low-cost, miniaturized channel sounding systems used in accurate and efficient channel propagation measurements at millimeter-wave frequencies.
TL;DR: This paper discusses early results associated with a fully-digital direct-conversion array receiver at 28 GHz that makes use of commercial off-the-shelf (COTS) electronics, including the receiver chain, installed on the Xilinx ZCU1275 prototyping platform.
Abstract: This paper discusses early results associated with a fully-digital direct-conversion array receiver at 28~GHz. The proposed receiver makes use of commercial off-the-shelf (COTS) electronics, including the receiver chain. The design consists of a custom 28~GHz patch antenna sub-array providing gain in the elevation plane, with azimuthal plane beamforming provided by real-time digital signal processing (DSP) algorithms running on a Xilinx Radio Frequency System on Chip (RF SoC). The proposed array receiver employs element-wise fully-digital array processing that supports ADC sample rates up to 2~GS/second and up to 1~GHz of operating bandwidth per antenna. The RF mixed-signal data conversion circuits and DSP algorithms operate on a single-chip RF SoC solution installed on the Xilinx ZCU1275 prototyping platform.
01 Nov 2019
TL;DR: In this paper, the authors examined the interference power distribution in an mmWave network employing beamforming transmission under different user association schemes, and contrast with those under omnidirectional transmission.
Abstract: We study the distribution of the interference power in a millimeter wave (mmWave) cellular network. Such interference is random and highly dependent on the employed transmission technique, as well as the varying channel conditions and the varying association between users and base stations. Traditional networks at lower frequencies usually employ omnidirectional transmission which creates an (almost) equal amount of interference in any direction. MmWave networks, however, must employ directional beamforming transmission in order to compensate for the high path loss in mmWave frequency bands. These directional transmissions drastically change the network interference structure. We examine the interference power distributions in an mmWave network employing beamforming transmission under different user association schemes, and contrast with those under omnidirectional transmission. Numerical results using an analytical mmWave channel model and a measurement-based channel generator, NYUSIM, show that beamforming not only reduces the amount of strong interference and hence significantly enhances network throughput, but also user association can considerably alter network interference and throughput structures.
Posted Content•
TL;DR: A programmable ultra-wideband sliding correlator-based channel sounder with high temporal and spatial resolution is designed in standard 65 nm CMOS, a critical block for future low-cost, miniaturized channel sounding systems used in accurate and efficient channel propagation measurements at millimeter-wave frequencies.
Abstract: A programmable ultra-wideband sliding correlator-based channel sounder with high temporal and spatial resolution is designed in standard 65 nm CMOS. The baseband chip can be configured either as a baseband transmitter to generate a pseudorandom spread spectrum signal with flexible sequence lengths, or as a baseband receiver with sliding correlator having an absolute timing reference to obtain power delay profiles of the multipath components of the wireless channel. The sequence achieved a chip rate of one Giga-bit-per-second, resulting in a multipath delay resolution of 1 ns. The baseband chip occupies an area of 0.66 mm x 1 mm with a power dissipation of 6 mA at 1.1 V in 65 nm CMOS. The sliding correlator-based channel sounder in this work is a critical block for future low-cost, miniaturized channel sounding systems used in accurate and efficient channel propagation measurements at millimeter-wave frequencies.
Posted Content•
TL;DR: Numerical results show that beamforming not only reduces the amount of strong interference and hence significantly enhances network throughput, but also user association can considerably alter network interference and throughput structures.
Abstract: We study the distribution of the interference power in a millimeter wave (mmWave) cellular network. Such interference is random and highly dependent on the employed transmission technique, as well as the varying channel conditions and the varying association between users and base stations. Traditional networks at lower frequencies usually employ omnidirectional transmission which creates an (almost) equal amount of interference in any direction. MmWave networks, however, must employ directional beamforming transmission in order to compensate for the high path loss in mmWave frequency bands. These directional transmissions drastically change the network interference structure. We examine the interference power distributions in an mmWave network employing beamforming transmission under different user association schemes, and contrast with those under omnidirectional transmission. Numerical results using an analytical mmWave channel model and a measurement-based channel generator, NYUSIM, show that beamforming not only reduces the amount of strong interference and hence significantly enhances network throughput, but also user association can considerably alter network interference and throughput structures.