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Clutter Loss Measurements and Modeling at 26 GHz Band

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Clutter loss refers to the power loss caused by clutter objects such as buildings and vegetation. The determination of clutter loss is crucial for the deployment of wireless communication networks. In this paper, we present results of clutter loss measurements at 26 GHz in a campus environment. The ITU-R P.2108-0 statistical clutter loss model is applied to model the clutter loss and the cumulative distribution functions (CDFs) of the measured and modeled clutter losses are compared, which show good agreement.
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URSI GASS 2020, Rome, Italy, 29 August - 5 September 2020
Clutter Loss Measurements and Modeling at 26 GHz Band
J. Huang, O. Zahid, and S. Salous*
Department of Engineering, Durham University, Durham, DH1 3LE U.K, *sana.salous@durham.ac.uk
Abstract
Clutter loss refers to the power loss caused by clutter
objects such as buildings and vegetation. The
determination of clutter loss is crucial for the deployment
of wireless communication networks. In this paper, we
present results of clutter loss measurements at 26 GHz in
a campus environment. The ITU-R P.2108-0 statistical
clutter loss model is applied to model the clutter loss and
the cumulative distribution functions (CDFs) of the
measured and modeled clutter losses are compared, which
show good agreement.
1 Introduction
As defined in ITU-R P.2108-0 [1], clutter refers to objects
such as buildings and vegetation, which are on the surface
of the earth but not terrain. Clutter loss is defined as the
difference in the transmission loss or basic transmission
loss with and without the presence of terminal clutter at
either end of the path with all other path details being the
same.
The determination of clutter loss is crucial for the
deployment of wireless communication networks, which
needs to be obtained from real clutter loss measurements.
Clutter loss measurements require one end of the link to
be above clutter level while the other terminal is in the
clutter. An illustration of clutter loss measurement setup is
shown in Fig. 1. At the transmitter (Tx) side, a horn
antenna is usually placed above the clutter for example on
the rooftop of a building and down tilted, while the
receiver (Rx) is behind clutter and equipped with an
omni-directional antenna.
Figure 1. An illustration of clutter loss measurements.
Only a few clutter loss measurements have been reported
in the literature below sub-6 GHz band, and in the
millimeter wave (mmWave) band. In [2], clutter loss
measurements were conducted in three cities in the US in
the 1755-1780 MHz band. The median clutter loss was
found to be 20-27 dB. In [3], the independent and joint
clutter loss and building entry loss were measured at 3.5
GHz. The results showed that the clutter loss and building
entry loss cannot be treated as multiplicative, and the
combined loss was related to the details of building
geometry and surrounding environment. In [4], clutter
loss measurements were conducted at two bands around
28 GHz and 38 GHz in an urban low-rise environment.
The clutter loss was found to depend on the placements of
the Tx and Rx antennas among buildings. In [5], clutter
loss measurements were conducted at 27 GHz in urban
campus environment. The maximum clutter loss was
about 35 dB. In [6, 7], clutter loss measurements were
conducted at 26 GHz and 40 GHz in suburban
environments in the range of 120-350 m. The clutter loss
with respect to the elevation angle range of 0°-5° was
analyzed. In addition, ray tracing simulation results were
compared with the measurement results. In [8], the clutter
loss and building entry loss were measured at 26 GHz.
Building entry loss was higher than clutter loss above the
median value due to measurements taken on the higher
floors. In [9], above rooftop channel measurements were
conducted in a suburban environment at 32.4 GHz. The
paths along the road, between houses, and on the roof
were measured. A site-specific path loss and clutter loss
model was proposed. In [10], an overview of the new
developed ITU-R P.2108-0 model was given. Extensive
measurements in Aalborg, Gothenburg, and Tokyo were
presented. The clutter loss in Aalborg was measured in a
residential area at 18 GHz band with distances up to 1.4
km. A clear increasing trend of clutter loss was found up
to 0.8 km, while it became constant for larger distances.
The clutter loss in Tokyo was measured at 2.2, 4.7, 26.4,
and 66.5 GHz in the range of 0.26-1.2 km.
In this paper, we present clutter loss measurements at 26
GHz, as it is one of the pioneer bandsin Europe and
identified by ITU WRC-19 recently for fifth generation
(5G) high data rate transmission. The results are
compared with the ITU-R P.2108-0 statistical clutter loss
model.
The remainder of the paper is organized as follows.
Section 2 describes the 26 GHz clutter loss measurements.
The ITU-R P.2108-0 statistical clutter loss model is
presented in Section 3. The measurement and modeling
results and analysis are given in Section 4. Finally,
conclusions are drawn in Section 5.
2 26 GHz Clutter Loss Measurements
The custom-designed channel sounder [11] is used to
conduct 26 GHz clutter loss measurements along three
routes at Durham University, behind buildings indicated
as (R1), (R2), and (R3), shown in Fig. 2(a)-(c). The Tx is
located at a height of about 18.2 m with a down tilt angle
of 12°, as shown in Fig. 2(d). The measured frequency
band is 24.68-27.68 GHz at a sweep repetition frequency
of 1.22 kHz. A horn antenna with 20 dBi gain and 18°
beamwidth is used at the Tx side, while an omni-
directional antenna is used at the Rx side with a height of
1.6 m. The main beam of the Tx antenna is adapted to
cover the three measurement routes, as shown in Fig. 2(e).
A total of 102, 150, and 47 positions were measured in R1,
R2, and R3, respectively. The corresponding Tx-Rx
distances were 50-80 m, 60-100 m, and 100-105 m for the
three routes, respectively.
(a) (R1)
(b) (R2)
(c) (R3)
(d) (Tx location)
(e) Measurement setup
Figure 2. Clutter loss measurement environments.
3 Statistical Clutter Loss Model
In ITU-R P.2108-0 recommendation, there are three
clutter loss models, for different terminal environments
and frequency ranges. The statistical clutter loss model for
the frequency range of 2-67 GHz is applied to model the
26 GHz clutter loss.
In the statistical clutter loss model, the input parameters
include frequency f (GHz), Tx-Rx distance d (km), and
percentage of locations p (%). The clutter loss not
exceeded for p% of locations for the terrestrial to
terrestrial path is given as
  log
 dB
(1)
 
(2)
 
(3)
where Q1(p/100) is the inverse complementary normal
distribution function, and are the long-range and
short-range clutter loss, respectively [10]. An illustration
of the median clutter loss calculated from the model is
shown in Fig. 3. As the frequency increases, the median
clutter loss becomes larger. Below the distance of about 1
km, the median clutter loss shows a linear relationship
with the distance in log scale. When the distance becomes
larger, the median loss does not change, i.e., goes to the
saturation range.
Figure 3. An illustration of the median clutter loss
calculated from the ITU-R P.2108-0 clutter loss model.
4 Results and Analysis
The measured power delay profile (PDP) is expressed as
PDP
   
(4)
where L is the number of multipath components (MPCs)
with powers above the threshold, and are the power
and delay of the lth MPC, respectively.
The clutter loss can be calculated as
CL
   
(5)
  

(6)
FSPL

(7)
where P and FSPL are the total path loss and free space
path loss, respectively.
The measured PDPs and path loss variations of R1, R2
and R3 are shown in Figs. 4-6, respectively. As can be
seen, R1 shows a low probability of clutter loss, which is
possible for a short link. R2 has the largest clutter loss as
the buildings are high and dense, which causes higher
losses. R3 has the smallest clutter loss variation, as the
distance variations are over a small range. The
measurement results show high correlation with the
building geometry and surrounding environments.
(a) Measured PDPs of R1.
(b) Path loss variations of R1.
Figure 4. Measured PDPs and path loss variations of R1.
(a) Measured PDPs of R2.
(b) Path loss variations of R2.
Figure 5. Measured PDPs and path loss variations of R2.
(a) Measured PDPs of R3.
(b) Path loss variations of R3.
Figure 6. Measured PDPs and path loss variations of R3.
The measured cumulative distribution functions (CDFs)
for R1, R2, and R3 are shown in Fig. 7. R1 has the
smallest clutter loss, while R2 has the largest clutter loss.
A comparison of the measured and modeled clutter losses
is shown in Fig. 8. For the statistical clutter loss model, as
the distance increases from 70 m to 90 m, the clutter loss
tends to be larger. For the measurement results, the
distance is in the range of 50-105 m. To avoid statistical
bias, the combined clutter loss values are re-sampled at
some distances. The measured combined CDF is closest
to the statistical clutter model when d = 80 m. The
measured median clutter loss is 11 dB, which is similar to
the statistical clutter model when d = 80 m. The
comparison shows a good match between measured and
modeled clutter loss.
Figure 7. CDFs of the measured clutter loss.
Figure 8. Comparison of the measured and modeled
clutter losses.
5 Conclusions
In this paper, results of measurements conducted at 26
GHz using the customized channel sounder at Durham
University were presented. The measurement data were
processed to extract clutter loss. The ITU-R P.2108-0
statistical clutter loss model was utilized to model the
clutter loss at 26 GHz band. The clutter loss is found to be
related to the building geometry and surrounding
environment and the measured and modeled clutter loss
have shown good agreement.
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
European Joint Research Centre, JRC, Ispra, Italy, EPSRC
under grant EP/I01049/1, PATRICIAN, and Intel, USA. The
authors would also like to acknowledge Amar Al-Jzari
and Mohamed Abdulali at Durham University for their
help in conducting the channel measurements.
7 References
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Low-altitude communication has attracted lots of attention in recent years, and it is very important to obtain an accurate clutter loss model for evaluating and designing such a communication system. For this purpose, we have conducted a channel measurement campaign at 5.8 GHz for suburabn low-altitude scenario. Based on the measured pathloss, we extract and analyze the clutter loss for different link distances and elevation angles between the transceiver. The measured clutter loss is validated by the ITU clutter loss model with respect to the link distance. Moreover, we compare the measured clutter loss with the the ITU clutter loss model with respect to the elevation angle, and find the obvious difference between them. Therefore, in this letter, we propose a modified clutter loss model and a pathloss model with respect to the elevation angle factor for the suburban low-altitude scenario.
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Applications of the unlicensed 60 GHz band include indoor wireless local area networks, outdoor short range communications and on body networks. To characterize the radio channel for such applications, a novel digital chirp sounder with programmable bandwidths up to 6 GHz with switched two transmit channels and two parallel receive channels for multiple-input multiple-output (MIMO) measurements was realized. For waveform durations of 819.2 μs, Doppler measurements can be performed up to 610 Hz for the single transmit and two receive configuration or 305 Hz for MIMO measurements. In this paper, we present the architecture of the sounder and demonstrate its performance from back to back tests and from measurements of rms delay spread, path loss and MIMO capacity in an indoor and an outdoor environment. For 20 dB threshold, the rms delay spread for 90% of the measured locations is estimated at 1.4 ns and 1 ns for the indoor and outdoor environments, respectively. MIMO capacity close to the iid channel capacity for 2 by 2 configuration is achieved in both environments.
2108-0, Prediction of clutter loss
  • Itu-R P
ITU-R P.2108-0, Prediction of clutter loss, June 2017.
Clutter loss measurements and simulations at 26 GHz and 40 GHz
  • B Montenegro-Villacieros
  • J Bishop
  • J.-M Chareau
B. Montenegro-Villacieros, J. Bishop, J.-M. Chareau, "Clutter loss measurements and simulations at 26 GHz and 40 GHz," in Proc. EuCAP'19, Krakow, Poland, Mar.-Apr. 2019, pp. 1-5.