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Frequency Dependence and Propagation Mechanisms of Path Loss in Indoor Environments
Abstract
This paper presents the frequency dependence of the path loss exponent (PLE) based on measurement results of multiple frequency bands in indoor environments and explains the propagation mechanisms that cause frequency dependence. Path loss measurements from 0.8 GHz to 66.5 GHz in two indoor open office environments were used to derive the parameters of a close-in free space reference distance model (CI model) and an alpha-beta-gamma model (ABG model). We revealed that the PLE of the single-frequency CI model tended to decrease with increasing frequency, while the frequency coefficient of the ABG model was smaller than that of the free space loss (FSPL), indicating a different frequency dependence than FSPL in these environments. Furthermore, the propagation mechanisms of the waveguide effect and the first Fresnel zone shielding cause this frequency dependence. Ray-tracing simulations revealed that the PLE becomes large and small in the low- and high-frequency bands, respectively, when the ceiling height is low, consistent with the measurements. The PLE becomes small regardless of the frequency band when the ceiling height is high, indicating frequency dependence along the propagation mechanism in both the ray-tracing simulation and measurement results.
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This letter provides a comparison of indoor radio propagation measurements and corresponding channel statistics at 28, 73, and 140 GHz, based on extensive measurements from 2014-2020 in an indoor office environment. Side-by-side comparisons of propagation characteristics (e.g., large-scale path loss and multipath time dispersion) across a wide range of frequencies from the low millimeter wave band of 28 GHz to the sub-THz band of 140 GHz illustrate the key similarities and differences in indoor wireless channels. The measurements and models show remarkably similar path loss exponents over frequencies in both line-of-sight (LOS) and non-LOS (NLOS) scenarios, when using a one meter free space reference distance, while the multipath time dispersion becomes smaller at higher frequencies. The 3GPP indoor channel model overestimates the large-scale path loss and has unrealistic large numbers of clusters and multipath components per cluster compared to the measured channel statistics in this letter.
Millimeter-wave (mmWave) and sub-Terahertz (THz) frequencies are expected to play a vital role in 6G wireless systems and beyond due to the vast available bandwidth of many tens of GHz. This paper presents an indoor 3-D spatial statistical channel model for mmWave and sub-THz frequencies based on extensive radio propagation measurements at 28 and 140 GHz conducted in an indoor office environment from 2014 to 2020. Omnidirectional and directional path loss models and channel statistics such as the number of time clusters, cluster delays, and cluster powers were derived from over 15,000 measured power delay profiles. The resulting channel statistics show that the number of time clusters follows a Poisson distribution and the number of subpaths within each cluster follows a composite exponential distribution for both LOS and NLOS environments at 28 and 140 GHz. This paper proposes a unified indoor statistical channel model for mmWave and sub-Terahertz frequencies following the mathematical framework of the previous outdoor NYUSIM channel models. A corresponding indoor channel simulator is developed, which can recreate 3-D omnidirectional, directional, and multiple input multiple output (MIMO) channels for arbitrary mmWave and sub-THz carrier frequency up to 150 GHz, signal bandwidth, and antenna beamwidth. The presented statistical channel model and simulator will guide future air-interface, beamforming, and transceiver designs for 6G and beyond.
This paper presents results of path loss measurements, in two indoor environments for both LoS and NLoS scenarios across a frequency range from 0.6-73 GHz using the multi-band custom designed channel sounders developed at Durham University. The data are analysed to estimate the path loss parameters for each frequency band with either the close in path loss model which assumes free space loss at 1 m reference distance and the floating intercept path loss model which estimates both parameters of the path loss model. The data across the multiple bands are then combined to generate a single set of coefficients for a frequency dependent path loss model. The median and 90% values of the rms delay spread values for a 20 dB threshold are presented across the frequency range of 0.6-39 GHz.
Recent research into radio propagation and large-scale channel modeling shows that frequencies can be used above 6 GHz for the new generation of mobile communications (5G). This article provides a detailed account of measurement campaigns that use directional horn antennas in co-polarization (V-V and H-H) and cross-polarization (V-H) in line-of-sight (LOS) and obstructed-line-of-sight (OLOS) situations between the transmitter and receptor; they were carried out in a corridor and computer laboratory located at the Federal University of Para (UFPA). The measurement data were used to adjust path loss prediction models of radio propagation, through the minimum mean square error (MMSE) method, for indoor environments in the frequencies of 8, 9, 10 and 11 GHz. The parameters for the models that were determined are as follows: path loss exponent (PLE), polarization exponent (co-and cross-polarization), effects of shadowing and path loss exponent for wall losses. Standard deviation and standard deviation point by point are included as statistical metrics. The approximations with regard to the large-scale path loss models for frequencies of 8, 9, 10 and 11 GHz show a convergence with the measured data, owing to the method employed for the optimization of the MMSE to determine the parameters of the model.
The 60 GHz frequency band enables the combination of high bandwidth free of interference and very high throughput WLANs such as 802.11ad, 802.11ay and maybe 5G. Propagation loss in millimeter-wave band may be a strong limitation to deployment and practical usage, in particular in non-line of sight. For this purpose, this paper presents 60 GHz channel sounding and throughput measurement results in an indoor residential environment. The presented results are focused on non-direct multipath characteristics that could be potentially used by smart antenna solution to extend 60 GHz communications in non-line of sight.
This paper presents path loss models based on extensive propagation measurements performed at 2.4 GHz and 5.8 GHz in a modern indoor office layout typical of small and medium-sized businesses, namely: the open-space office. Measurements were conducted using a vector network analyzer which covers frequencies up to 6 GHz, and ultra-wideband omnidirectional vertically-polarized antennas. The data were recorded under the same conditions and with the same antennas for both 2.4 GHz and 5.8 GHz. 940 transmitter-receiver location and height combinations were studied, as well as antenna configurations in both line-of-sight and non-line-of-sight. A second measurement campaign was conducted to quantify the variation amount on the expected power loss in realistic scenarios that include the effect of people movement and showed that the mean path loss further increases by up to 4 dB due to people's presence and movement, with variations up to 9 dB when the activity level is high.
This paper presents millimeter-wave propagation measurements for urban micro-cellular and indoor office scenarios at 28 GHz and 73 GHz, and investigates the corresponding path loss using five types of path loss models, the single-frequency floating-intercept (FI) model, single-frequency close-in (CI) free space reference distance model, multi-frequency alpha-beta-gamma (ABG) model, multi-frequency CI model, and multi-frequency CI model with a frequency-weighted path loss exponent (CIF), in both line-of-sight and non-line-of-sight environments. Results show that the CI and CIF models provide good estimation and exhibit stable behavior over frequencies and distances, with a solid physical basis and less computational complexity when compared with the FI and ABG models. Furthermore, path loss in outdoor scenarios shows little dependence on frequency beyond the first meter of free space propagation, whereas path loss tends to increase with frequency in addition to the increased free space path loss in indoor environments. Therefore, the CI model is suitable for outdoor environments over multiple frequencies, while the CIF model is more appropriate for indoor modeling. This work shows that both the CI and CIF models use fewer parameters and offer more convenient closed-form expressions suitable for analysis, without compromising model accuracy when compared to current 3GPP and WINNER path loss models.
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 l- ss data and closed-form optimization formulas for all path loss models are given in the Appendices.
This paper presents 28 GHz and 73 GHz millimeter- wave propagation
measurements performed in a typical office environment using a 400
Megachip-per-second broadband sliding correlator channel sounder and highly
directional steerable 15 dBi (30 degrees beamwidth) and 20 dBi (15 degrees
beamwidth) horn antennas. Power delay profiles were acquired for 48
transmitter-receiver location combinations over distances ranging from 3.9 m to
45.9 m with maximum transmit powers of 24 dBm and 12.3 dBm at 28 GHz and 73
GHz, respectively. Directional and omnidirectional path loss models and RMS
delay spread statistics are presented for line-of-sight and non-line-of-sight
environments for both co- and cross-polarized antenna configurations. The LOS
omnidirectional path loss exponents were 1.1 and 1.3 at 28 GHz and 73 GHz, and
2.7 and 3.2 in NLOS at 28 GHz and 73 GHz, respectively, for
vertically-polarized antennas. The mean directional RMS delay spreads were 18.4
ns and 13.3 ns, with maximum values of 193 ns and 288 ns at 28 GHz and 73 GHz,
respectively.
Modelling of path loss behaviour in ultra wideband radio channels was revisited. Although simple but realistic standardized channel models have already been established, this paper attempts to provide detailed insights about the precision of the standardized model based on an extensive measurement campaign which covered whole areas inside an office room. Attention was paid to the frequency and distance dependency of path loss and their interrelation. It was found that the two dependencies can be modelled separately as the standardized UWB channel model assumed. Furthermore, this paper clarified the path loss modelling methodology to combat an ambiguous and non-unified model parameter derivation procedure. Finally, model parameters for path loss and shadow fading were derived based on the clarified method to complement the channel model parameter set.
This paper provides the results of indoor radio propagation measurements at current and potential wireless LAN frequency bands, 2.4, 5.2 10, 17 and 24 GHz in the Moore laboratory at Caltech. Three scenarios (floor to floor in the hall, a line-of-sight path down the hall, and a non line-of-sight path from office to hall) were considered. The loss in going from floor to floor increased with frequency from 15 dB at 2.4 GHz to 50 dB at 24 GHz. In addition, for the line-of- sight path, we found a path loss exponent n less than 2, indicating a guiding effect of the hall. The non line-of-sight path shows a loss exponent n that is larger than 2, indicating scattering. We found that the rms delay spread decreased with frequency inside a room, but increased with frequency along a non-line-of-sight path.
The tremendous growth of mobile radio systems and the future
requirements for PCS will create a need for additional communication
networks, particularly in densely populated urban areas where future
generations of mobile systems will be introduced. System designers and
radio frequency spectrum planners will require a detailed knowledge of
indoor channel characteristics such as path loss, channel fading and
pulse delays etc. The computation of path loss is of great importance to
the planning of wireless indoor communication systems. Propagation
measurements were performed at 450 MHz, 900 MHz, 1.35 GHz and 1.89 GHz
in the corridors on the second, first and ground floors of an
Institute's building. A computer simulation tool was adopted for the
calculation of channel parameters. Values of path loss exponent `n',
standard deviation, RMS delay spread, a measure for the spreading of the
received signal and Rice factor `k' were evaluated using experimental
and simulated data. The Rice factor was found to vary between 0.2 to
9.60
Because of the potential implementation of indoor wireless local
area networks (LANs) and personal communication networks (PCNs) it is
important to understand propagation of signals in the UHF band inside
buildings. The authors explore features of office buildings of modern
construction that influence propagation between transmitter and receiver
located on the same floor. One feature is the clear space between
ceiling and furnishings or floor that results in excess attenuation of
the signal. A second feature is reflection and transmission at interior
and exterior walls. Diffraction at corners and propagation along the
exterior wall are also shown to be a significant means for radiation to
reach the receivers. The influences of the first two features are
combined into a computer program that evaluates the sector average
signal, which is then compared with measurements
Channel model considering frequency dependency based on propagation measurements with multiple frequencies for 5G systems
- Sasaki
Path loss measurements and modeling for indoor office scenario at 28 and 38 GHz
- Kim
Channel model considering frequency dependency based on propagation measurements with multiple frequencies for 5G systems
- M Sasaki
- M Inomata
- W Yamada
- N Kita
- T Onizawa
- M Nakatsugawa
Path loss measurements and modeling for indoor office scenario at 28 and 38 GHz
- M.-D Kim
- J Liang
- J Lee
- J Park
- B Park