Ultra-wideband millimeter-wave (mmWave) propagation measurements were conducted in the 28- and 73-GHz frequency bands in a typical indoor office environment in downtown Brooklyn, New York, on the campus of New York University. The measurements provide large-scale path loss and temporal statistics that will be useful for ultra-dense indoor wireless networks for future mmWave bands. This paper presents the details of measurements that employed a 400 Megachips-per-second broadband sliding correlator channel sounder, using rotatable highly directional horn antennas for both co-polarized and crosspolarized antenna configurations. The measurement environment was a closed-plan in-building scenario that included a line-of-sight and non-line-of-sight corridor, a hallway, a cubicle farm, and adjacent-room communication links. Well-known and new single-frequency and multi-frequency directional and omnidirectional large-scale path loss models are presented and evaluated based on more than 14 000 directional power delay profiles acquired from unique transmitter and receiver antenna pointing angle combinations. Omnidirectional path loss models, synthesized from the directional measurements, are provided for the case of arbitrary polarization coupling, aswell as for the specific cases of co-polarized and cross-polarized antenna orientations. The results show that novel large-scale path loss models provided here are simpler and more physically based compared to previous 3GPP and ITU indoor propagation models that require more model parameters and offer very little additional accuracy and lack a physical basis. Multipath time dispersion statistics formmWave systems using directional antennas are presented for co-polarization, crosspolarization, and combined-polarization scenarios, and show that the multipath root mean square delay spread can be reduced when using transmitter and receiver antenna pointing angles that result in the strongest received power. Raw omnidirectional path loss data and closed-form optimization formulas for all path loss models are given in the Appendices.

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Indoor Office Wideband Millimeter-Wave Propagation Measurements and Channel Models at 28 and 73 GHz for Ultra-Dense 5G Wireless Networks

In this paper we provide a thorough and up to date survey of path loss prediction methods, spanning more than 60 years of fairly continuous research. These methods take a variety of approaches to modeling the signal attenuation between wireless transceivers: purely theoretical models, empirically fitted (often statistical) models, deterministic ray-optical models, and measurement-directed methods. Our work here extends and updates excellent, but now dated prior surveys of this important field. We provide a new taxonomy for reasoning about the similarities and differences of the many approaches and provide a brief but complete overview of the various methods as well as describing insights into future directions for research in this area.

A Survey of Wireless Path Loss Prediction and Coverage Mapping Methods

The rapid growth of Internet-of-Things (IoT) in the current decade has led to the development of a multitude of new access technologies targeted at low-power, wide area networks (LP-WANs). However, this has also created another challenge pertaining to technology selection. This paper reviews the performance of LP-WAN technologies for IoT, including design choices and their implications. We consider Sigfox, LoRaWAN, WavIoT, random phase multiple access (RPMA), narrowband IoT (NB-IoT), as well as LTE-M and assess their performance in terms of signal propagation, coverage and energy conservation. The comparative analyses presented in this paper are based on available data sheets and simulation results. A sensitivity analysis is also conducted to evaluate network performance in response to variations in system design parameters. Results show that each of RPMA, NB-IoT, and LTE-M incurs at least 9 dB additional path loss relative to Sigfox and LoRaWAN. This paper further reveals that with a 10% improvement in receiver sensitivity, NB-IoT 882 MHz and LoRaWAN can increase coverage by up to 398% and 142%, respectively, without adverse effects on the energy requirements. Finally, extreme weather conditions can significantly reduce the active network life of LP-WANs. In particular, the results indicate that operating an IoT device in a temperature of −20 °C can shorten its life by about half; 53% (WavIoT, LoRaWAN, Sigfox, NB-IoT, and RPMA) and 48% in LTE-M compared with environmental temperature of 40 °C.

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Low-Power Wide Area Network Technologies for Internet-of-Things: A Comparative Review

Ubiquitous and pervasive networks and applications include a growing number of research themes. In most use cases, applications require location information to interpret their environment and behave accordingly. In this paper, location algorithms and positioning methods that can be used for wireless geolocation are presented.

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Survey of Wireless Geolocation Techniques

Method and arrangement in a user equipment for transmitting scheduling requests to a base station The base station is adapted to serve the user equipment The user equipment is configured to transmit scheduling requests to the base station only at certain predetermined scheduling request opportunities The method comprises triggering a scheduling request transmission, transmitting a scheduling request to the base station at the next occurring scheduling request opportunity, starting a scheduling request prohibiting timer and prohibiting any further scheduling request retransmission at future scheduling request opportunities while the scheduling request prohibiting timer is running Also, a corresponding method and arrangement in a base station is described

Method and arrangement in a wireless communication system

Empirical propagation models have found favour in both research and industrial communities owing to their speed of execution and their limited reliance on detailed knowledge of the terrain. Although the study of empirical propagation models for mobile channels has been exhaustive, their applicability for FWA systems is yet to be properly validated. Among the contenders, the ECC-33 model, the Stanford University Interim (SUI) models, and the COST-231 Hata model show the most promise. In this paper, a comprehensive set of propagation measurements taken at 3.5 GHz in Cambridge, UK is used to validate the applicability of the three models mentioned previously for rural, suburban and urban environments. The results show that in general the SUI and the COST-231 Hata model over-predict the path loss in all environments. The ECC-33 models shows the best results, especially in urban environments.

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Comparison of empirical propagation path loss models for fixed wireless access systems

This paper examines the temporal characteristics of the fixed wireless access channel resulting from the combined effects of foliage and wind. Measurements at a frequency of 3.5 GHz taken over the course of one year are presented. The temporal variability of the path loss is shown to be well approximated by a Rician process. The dependency of the median K factor on excess path loss, average wind speed and season is investigated. An empirical expression for the median K factor encompassing these variables is presented. The median K factor is found to be approximately inversely proportional to average wind speed.

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Time variability of the foliated fixed wireless access channel at 3.5 GHz

A low complexity, stabilized precoder for broadband indoor radio is presented, which uses radial root reduction for stability, and so avoids the use of a module operator. Simulations show that the stabilized precoder has comparable performance to Tomlinson-Harashima (1971) precoding with perfect automatic gain control (AGC), and is immune to AGC fluctuations which degrade the performance of TH precoding.

Stabilized precoder for indoor radio communications

This paper presents the results of propagation measurements at 3.5 GHz for a broadband fixed wireless access (BFWA) system with a directional subscriber antenna and a sectored base station antenna. First we describe the equipment and data processing methods used for extracting the channel impulse response. This is followed by the results of narrowband path loss measurements, and the statistics of the root mean squared (RMS) delay spread, with respect to subscriber unit (SU) antenna height. We show the influence of SU antenna height on a BWA system employing directional SU antennas and sectored base station antennas at 3.5 GHz. The path loss exponent at a SU antenna height of 10 m is close to 4, and between 2.2 and 2.7 for SU antenna heights between 7 m and 9 m. The wideband characteristics of the BWA channel, as quantified by the RMS delay spread show that 90 % of the channels have a delay spread of less than 100 ns. The average RMS delay spread is also observed to decrease with increasing SU antenna height. The maximum RMS delay spread observed in our measurements is less than 270 ns.

Wideband channel measurements and characterisation for broadband wireless access

Multipath fading is a major obstacle to be overcome in achieving high data rates for wireless LANs. Powerful equalizers needed to combat multipath are costly in terms of processing power, training sequence overhead and training time. In time-division-duplex radio systems, precoding may be used to shift the equalization burden from the receiver to the transmitter, enabling significant reductions in complexity and transmission overhead. This article describes a stabilized precoder with switched antenna diversity which achieves simple and efficient precoding for wireless LANs.

M.P. Sellars

Papers

Comparison of empirical propagation path loss models for fixed wireless access systems

Time variability of the foliated fixed wireless access channel at 3.5 GHz

Stabilized precoder for indoor radio communications

Wideband channel measurements and characterisation for broadband wireless access

Stabilized precoder with antenna diversity for wireless LANs