![displays the CDF of the angular spread values for the two measured frequency bands. The estimated angular spread of both bands varies in a range between 40⁰ and 95⁰ which is found to be larger than the angular spread values in the outdoor environments [8]. This is due to the large number of reflectors and scatterers within the indoor scenarios. The 50% and 90% CDF values of the angular spread and the corresponding standard deviation (í µí¼ ∅ í µí°´í µí± ) are given in Table 4. From this table, it can be seen a maximum difference of ~10⁰ between the two measured bands for both the 50% and 90% values of the CDF values.](https://www.researchgate.net/profile/Amar-Al-Jzari/publication/354872639/figure/fig2/AS:1072786554490881@1632783654553/displays-the-CDF-of-the-angular-spread-values-for-the-two-measured-frequency-bands-The_Q320.jpg)
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URSI GASS 2021, Rome, Italy, 28 August - 4 September 2021
Millimeter-Wave Indoor Channel Characterization based on Directional
Measurements at 39 GHz and 70 GHz
Amar Al-jzari, Mohamed Abdulali, and Sana Salous*
Department of Engineering, Durham University, Durham, DH1 3LE UK, * sana.salous@durham.ac.uk
Abstract
This paper presents results of wideband channel
measurements at 39 GHz and 70 GHz in a typical indoor
office environment. Measurements were carried out using
Durham University’s multi-band frequency modulated
continuous wave channel sounder. The propagation
characteristics at different angular orientations are
estimated and compared for both frequency bands. The
effects of the antenna pattern on the propagation channel
parameters such as the average power delay profile, root
mean square delay spread, and angular spread, are
analyzed. The results show similar propagation properties
for both measured bands.
1 Introduction
The millimeter-wave (mmWave) band with a large
transmission bandwidth is viewed as key for (5G) wireless
systems. The use of the mmWave band will considerably
extend the channel capacity of indoor wireless networks [1,
2]. Therefore, indoor channel measurements at these
frequency bands are essential for a good understanding of
the propagation characteristics for the design of 5G radio
networks [3, 4]. Recently, several channel measurements at
different mmWave bands have been reported in various
indoor environments to study the propagation channel
characteristics [5, 6]. However, few studies have dealt with
the effects of the antenna directivity and the channel
characteristics at 39 GHz and 70 GHz in an indoor
environment.
In this paper, we present wideband indoor channel
measurements in two of the frequency bands (39 GHz and
70 GHz) identified by the World Radiocommunications
Conference in 2019 (WRC-19) for 5G wireless
communication systems. The present measurements were
performed using the rotated directional antenna-based
(RDA) method. Wideband channel parameters such as the
root mean square (rms) delay spread, and the average
power delay profile (PDPs) were measured and
investigated for different angular directions between the
transmitter (Tx) and the receiver (Rx) antennas. The
angular spread as well as the effects of the antenna
beamwidth on the channel characteristics, are measured
and estimated.
The rest of the paper is organized as follows. Section 2
describes the indoor channel measurements. Section 3
explains the measured data processing procedure. Section
4 covers the measurement results and analysis. Finally,
conclusions are drawn in Section 5.
2 Channel Measurements
A custom-designed frequency modulated continuous wave
(FMCW) channel sounder developed at Durham
University [7] was used to conduct LoS measurements in
an indoor office environment shown in Fig. 1 (a), with the
corresponding Tx and Rx locations in Fig. 1(b). The
measurements were conducted with 6 GHz and 4.5 GHz
bandwidth centered at 70 GHz and 38.5 GHz, respectively,
at a repetition frequency of 1.22 kHz. An omnidirectional
antenna was used at the transmitter, set up at ~ 2.3 m from
the ground, and horn antennas at the Rx (beamwidths as in
Table 1) at a height of ~ 1.6 m. The two frequency bands
were measured in two runs at 14 Rx locations. To
investigate the directional channel parameters in the
angular domain, a CCTV positioner rotates the horn
antenna in 10⁰ steps to cover the full rotation in the azimuth
plane. To study the effects of the antenna beamwidth on the
propagation characteristics, three locations (marked with a
red circle) in Fig. 1 (b) were measured with both horn
antennas, while the rest of the locations were measured
with the 18⁰ beamwidth antenna. Table 1 provides a
summary of the measurement parameters.
(a) (b)
Figure 1. (a) Photo of the measured scenario. (b) Layout
of the measured scenario.
Table 1. Channel measurement parameters.
Freq. bands
(GHz)
67-73
37-41.5
RF BW (GHz)
6
4.5
Analysis BW (GHz)
2
1.5
Tx Antenna
Omnidirectional
Rx Antenna
(gain, beamwidth)
(20 dBi, 18⁰)
(10 dBi, 55⁰)
3 Data Processing Method
The measured data were analyzed to obtain the power delay
profile (PDP) at each angular rotation. Different relative
channel parameters including the root mean square (rms)
delay spread, angular spread, and the received power were
then estimated from the measured PDP.
The rms delay spread and the angular spread are estimated
using equations 1 and 2 [7-8]
(1)
where N is the total number of delay bins in each PDP,
and are the delay and the power of the nth path.
(2)
where L is the total number of angles per location and ()
is the received power at each azimuth angle .
4 Measurement Results and Analysis
4.1 Power Delay Profile (PDP)
Fig. 2 shows an example of the measured PDPs versus the
receiver rotation angle at location Rx7. In both measured
frequency bands, strong components can be received in the
boresight angles from ~ 250⁰ to ~ 280⁰ when the Rx antenna
was oriented towards the Tx antenna. Wall reflected
components can be detected in the non-boresight angles
from ~ 50⁰ to ~ 100⁰ when the Rx antenna was facing away
from the Tx antenna. The figure shows significant
differences in the measured PDPs due to employing
different antenna beamwidths. It can be seen that the high
gain horn antenna enhances the power of the received LoS
and the obstructed multipath components in both measured
bands.
(a) 39 GHz, 18⁰ beamwidth.
(b) 39 GHz, 55⁰ beamwidth.
(c) 70 GHz, 18⁰ beamwidth.
(d) 70 GHz, 55⁰ beamwidth.
Figure 2. Measured PDPs with different horn antenna
beamwidths versus the Rx rotation angle.
4.2 Delay Dispersion Properties
The rms delay spread was estimated for a 20 dB threshold.
Fig. 3 shows the cumulative distribution function (CDF) of
the rms delay spread values where the delay spread was
classified as LoS when the receive antenna main beam was
oriented towards the transmitter and obstructed LoS
(OLoS) when the receive antenna main beam was rotated
away from the transmit antenna. It can be seen in both
measured frequency bands, that when the antenna was
oriented away from the receiver (OLoS), the rms delay
spread values are larger compared with the LoS orientation
due to the obstruction of the strongest LoS component and
the presence of several multipath components as seen in
Fig. 2. A Gaussian Normal distribution (, ) was used
to fit the CDFs of the rms delay spread. The 50% and 90%
CDF values of the rms delay spread as well as the estimated
distribution parameter are given in Table 2 which
indicates a maximum difference of ~1.6 ns between the two
bands for both the 50% and 90% of the CDF values.
(a)
(b)
Figure 3. CDF of the rms delay spread with horn antenna
with 18⁰ beamwidth (a) 39 GHz, (b) 70 GHz.
Table 2. rms delay spread statistics in (ns).
Beam
direction
67-73 GHz
37-41.5 GHz
CDF: 50%, 90%;
CDF: 50%, 90%;
LoS
4.75, 6.33; 1.90
3.14, 7.37; 2.16
OLoS
12.17, 23.43; 7.57
11.46, 22.28; 7.07
The rms delay spread values for the two antenna
beamwidths are given in Table. 3, where the delay spread
values are presented for the LoS angle and the mean value
for the OLoS angles. For the OLoS, the rms delay spread
for both frequency bands is higher by less than 1 ns for the
high gain antenna. However, for the LoS case a difference
of 2.2 ns is detected for the mean value at 70 GHz. While
the broader antenna beamwidth would capture more
multipath reflections, the higher gain of the narrower beam
antenna enhances the strength of the multipath components
leading to higher rms delay spread values.
Table 3. Directional rms delay spread in (ns) for different
antenna beamwidths.
Rx
Loc.
Rx Ant.
(gain, beam)
67-73 GHz
37-41.5 GHz
LoS
OLoS
LoS
OLoS
Rx3
(20 dBi, 18⁰)
5.6
11.7
6.6
12.01
(10 dBi, 55⁰)
3.8
10.8
5.7
11.4
Rx4
(20 dBi, 18⁰)
8.3
12.3
7.9
11.01
(10 dBi, 55⁰)
3.4
12.9
6.3
9.4
Rx7
(20 dBi, 18⁰)
5.7
12.4
3.9
10.4
(10 dBi, 55⁰)
5.7
10.4
5.2
10.2
Mean
(20 dBi, 18⁰)
6.5
12.1
6.1
11.4
(10 dBi, 55⁰)
4.3
11.2
5.7
10.3
4.3 Angular Dispersion Properties
Fig. 4 displays the CDF of the angular spread values for the
two measured frequency bands. The estimated angular
spread of both bands varies in a range between 40⁰ and 95⁰
which is found to be larger than the angular spread values
in the outdoor environments [8]. This is due to the large
number of reflectors and scatterers within the indoor
scenarios. The 50% and 90% CDF values of the angular
spread and the corresponding standard deviation () are
given in Table 4. From this table, it can be seen a maximum
difference of ~10⁰ between the two measured bands for
both the 50% and 90% values of the CDF values.
Figure 4. CDF of the angular spread with horn antenna
with 18⁰ beamwidth for both frequency bands.
Table 4. Angular spread statistics in (degrees).
CDF: 50%, 90%;
Frequency
LoS scenario
67-73 GHz
62.06, 89.29; 16.61
37-41.5 GHz
53.12, 79.03; 15.33
Table 5 illustrates the impact of the antenna beamwidth on
the measured angular spread. The results show different
antenna directivity can produce various angular spread
values due to multiple reflections within the measured
scenario. As seen from Table 5, it can be identified that a
high gain horn antenna has higher angular spread with
mean values of ~60⁰ and 84.2⁰ at 70 GHz and 39 GHz,
respectively.
Table 5. Angular spread in (degrees) for different antenna
beamwidths.
Rx
Loc.
Rx Ant.
(gain, beam)
67-73 GHz
37-41.5 GHz
LoS
LoS
Rx3
(20 dBi, 18⁰)
53.12
90.19
(10 dBi, 55⁰)
37.77
79.01
Rx4
(20 dBi, 18⁰)
47.01
91.49
(10 dBi, 55⁰)
37.48
78.01
Rx7
(20 dBi, 18⁰)
79.82
70.79
(10 dBi, 55⁰)
55.87
82.44
Mean
(20 dBi, 18⁰)
59.98
84.2
(10 dBi, 55⁰)
43.71
79.82
5 Conclusions
In this paper, we present indoor channel measurements
conducted in an office scenario at two of the frequency
bands agreed in WRC-19 for 5G wireless communication
systems. The data were analyzed to extract different
propagation channel characteristics. The presented results
for both bands show larger delay spread values are
observed when the transmitter and the receiver antenna
main beams are not aligned. Due to the large number of
multipath components in an indoor environment, higher
angular spread values were obtained in the indoor scenario
for both measured bands compared with outdoor scenario.
Moreover, the impact of the antenna directivity on the
propagation characteristics have been investigated. Further
studies will be performed in the future to investigate the
directional propagation channel characteristics for both
frequency bands at an industrial (factory) environment.
6 Acknowledgements
The authors would like to acknowledge the support of
WaveComBE project, under Horizon 2020 research and
innovation program, grant agreement No. 766231. The 60
GHz sounder was developed under the EPSRC grant
PATRICIAN EP/I00923X/1 and further funding from
EPSRC Impact Acceleration Account.
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