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OPRA
Orthogonal Polarization Reuse Antenna
version 1.0
Apr. 2021
Abstract
In mobile communications, increasing capacity and extending coverage are
the most important factors to operators.
KMW implemented OPRA that has applied Orthogonal Polarization Reuse to
increase capacity and extend coverage simultaneously.
OPRA reuses different orthogonal polarizations on multi-beam, significantly
reducing the correlation between beams, and increasing capacity by 36% and
coverage by 39%. This OPRA technology can be implemented in both the RF
domain and digital domain.
the ability
OPRA technology gives operators^to achieve increased capacity and extended
coverage at a low investment cost, and paramountly reducing CapEx and OpEx.
KMW is ready to offer a variety of RU products powered by OPRA technology
to global partners and customers.
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Introduction
[ Background ]
Operators have continued to demand solutions that simultaneously increase
capacity and coverage at a low investment. However, none of the solutions
could satisfy these conditions. 5G uses RRH-type products for services coverage
improvement and mMIMO RU products for services capacity improvement. This
costs, a significant
leads to an increase in the cost that is an obstacle to expanding the 5G market.
Therefore, a new solution would significantly reduce the operators’ CapEx and
OpEx, contributing to the expansion of the 5G market.
[ Orthogonal Polarization Reuse ]
Efforts to increase capacity and extend coverage have continued through antenna
advancements.
technology.^ Increasing capacity by dual orthogonal polarization technology and
extending coverage by narrow multi-beam are the best examples. However, dual
orthogonal polarization technology results in deterioration of capacity due to
correlation by the overlap of polarization in multiple MIMO environments, and
narrow multi-beam technology has a limitation that extends coverage. However,
capacity increases are low due to the correlation between antenna polarizations.
The limitations of these technologies occur because the same polarization is used
in the same space, at the same time, and at the same frequency.
Orthogonal Polarization Reuse, a technique that reuses different polarizations by
separating time, space, and frequency, is a new paradigm that satisfies capacity
increase and coverage extension by reducing correlation by existing polarization.
through
VH
±45°
±45°
VH
DL
±45°
Space
UL
V/H
DL
±45°
UL
V/H
f1
±45°
Time
f2
V/H
Frequency
--- Orthogonal Polarization Reuse ---
[ OPRA (Orthogonal Polarization Reuse Antenna) ]
OPRA is an Orthogonal Polarization Reuse technology that uses different dual
orthogonal polarizations. The representative polarizations used are Slant 45°(±45°)
polarization and Vertical / Horizontal(V/H) polarization. OPRA reuses different
dual orthogonal polarizations by separating time, space, and frequency to reduce
correlation by polarization and increasing capacity, and extending coverage.
RU products that use KMW’s OPRA are expected to reduce operators’ concerns
and costs.
OPRA
Technology
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▲
36% 9% ▲
3
city
Capa erage
o
C v
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How to increase
capacity and
extend
coverage?
The reason is why the coverage and capacity do not double up, even if 3-sectors
are subdivided further than 6 -sectors, is because capacity is deteriorated as
correlation by interference and polarization by adjacent beams between each
sector. Similarly, using the Narrow Multi-beam within the same sector does not
increase capacity because of the correlation caused by polarization between
Narrow Multi-beam if the same antenna polarization is used.
±45°
±45°
±45°
±45°
--- Inter-beam interference due to same polarization reuse ---
OPRA forms narrow multiple beams in different directions and intersects two
different dual orthogonal polarizations between the beams. Because OPRA uses
two different pairs of dual orthogonal polarizations between beams in a spaceisolated with different directions. It reduces correlation by polarization between
beams. Therefore, the correlation caused by the polarization between adjacent
beams is minimized and increasing capacity and extending coverage.
review highlighted sentence
VH
±45°
±45°
VH
--- OPRA technology by orthogonal polarization reuse ---
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OPRA’s
Performance
[ Performance Comparison by Simulation ]
To verify the performance of OPRA implemented by KMW, capacity and coverage
are compared by simulating three cases of 4x4 MIMO.
±45° x2
±45°
Conventional
±45°
VH
Twin Beam
±45°
OPRA
Conventional Antenna Technology uses the same ±45° polarization as a sector
beam, and Twin Beam uses the narrow multi-beam with the same ±45° polarization.
But as for OPRA, one beam on the narrow multi-beam uses ±45° polarization, and
the other beam uses V/H (Vertical/Horizontal) polarization.
Simulation parameters are summarized in the table below.
Category
System
Configuration
Channel
Model
Value
Parameter
Carrier Frequency
3.5GHz
Channel Bandwidth
100MHz
BS Transmit power
160W(40W/path)
Conventional ANT Gain
17.5dBi
Twin Beam ANT Gain
19.5dBi
OPRA ANT Gain
19.5dBi
Polarized Channel Model
Urban Macro
Inter-site distance
500m
BS ANT height
30m
UE ANT configuration
4Rx with V/H polarization
1.5m~22.5m for indoor UE(80%)
1.5m for outdoor UE(20%)
UE ANT height
Capacity comparison
Capacity is increased by 36% in OPRA over Conventional. We can see the effect
of OPRA reducing correlation by separating and reusing different orthogonal
polarizations as it is extended by 28% compared to Twin Beam that uses the same
narrow band within the same polarization.
150%
100%
136%
108%
100%
50%
0
Conventional
Twin Beam
OPRA
--- Capacity Comparison --COPYRIGHT©2021KMW.ALL.RIGHTS RESEERVED.
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Coverage comparison
Coverage is extended by 39% in OPRA over Conventional. We can see the effect
of OPRA on reducing correlation by separating and reusing different orthogonal
polarizations as it is extended by 15% compared to twin beam.
OPRA
Twin Beam
Conventional
139%
124%
100%
--- Coverage Comparison ---
Multi-Sectors & Cell Performance
There are many sectors and cells, which lead to an increase in Inter-cell
Interference, resulting in capacity degradation. OPRA is expected to increase
capacity performance in Multi-Sectors & Cells due to its effect on reducing
interference between beams.
A
sector
sector
C
B
Conventional
OPRA
--- 3-Sector, 4x4 MIMO, Full Interference ---
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The graph below compares the performance of OPRA in a 3-sector full interference
environment.
155%
150%
130%
100%
100%
50%
0
Conventional
OPRA
Twin Beam
--- OPRA 3-Sector Capacity Comparison ---
[ Field test comparison ]
The performance of OPRA has also been shown in field tests. The following are
the result through 4T4R RU in the n78 band of 5G NR.
The rank index 4 received from the user equipment increased in OPRA over
Conventional through the field test.
Conventional
OPRA
5G KPI5G KPI per NR-ARFCN
(Based on PCell only)NR-ARFCN
633918 RF RI(test)
Rank 4 (38.99%, 434)
Rank 3 (42.50%, 473)
Rank 2 (15.00%, 167)
Rank 1 (3.5%, 39)
5G KPI5G KPI per NR-ARFCN
(Based on PCell only)NR-ARFCN
633918 RF RI(test)
Rank 4 (46.11%, 682)
Rank 3 (34.75%, 514)
Rank 2 (16.90%, 250)
Rank 1 (2.33%, 33)
Conventional
45%
OPRA
46%
43%
39%
35%
35%
25%
17%
15%
15%
5%
0
3%
2%
Rank 1
Rank 2
Rank 3
Rank 4
--- Field Test Result --COPYRIGHT©2021KMW.ALL.RIGHTS RESEERVED.
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OPRA’s
Benefits
OPRA achieves capacity increase and coverage extension by narrow multiple
beams and orthogonal polarization reuse without adding more signal paths,
complex configurations, or calculations.
Therefore we expect that, for example, 8T8R RU powered by OPRA will closely
meet the performance of 32T32R massive MIMO.
The graph below compares the simulated capacity performance of OPRA and
mMIMO RU.
154%
150%
100%
136%
160%
100%
50%
0
4T4R
Conventional
4T4R
OPRA
8T8R
OPRA
32T32R
mMIMO
--- OPRA & mMIMO RU Capacity Comparison ---
Besides, OPRA is expected to broaden the operator’s choices by providing new
applications through the extension of time, and frequency.
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Conclusion
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References
KMW introduced OPRA technology, and it has been academically published in
ISAP2020 and under review on IEEE Transaction Antenna & Propagation. All related
patents have also been applied.
OPRA technology has shown the ability to increase capacity and to extend
coverage, which can significantly reduce CapEx and OpEx.
KMW is ready to offer a variety of RU products powered by OPRA to global
partners and customers.
(1) 3GPP, "Study on Channel Model for Frequencies from 0.5 to 100GHz"
3rd Generation Partnership Project (3GPP), TR 38.901 V15.0.0, Jun. 2019
(2) R. A. Andrews, P. P. Mitra, and R. deCarvalho,
"Tripling the capacity of wireless communications using electromagnetic
polarization" Nature, vol. 409, pp. 316–318, Jan. 2001.
(3) M. Dao, V. Nguyen, Y. Im, S. Park, and G. Yoon,
"3D polarized channel modeling and performance comparison of mimo
antenna configurations with different polarizations" IEEE Transactions on
Antennas and Propagation, vol. 59, no. 7, pp. 2672–2682, 2011.
(4) Takaaki Beni, Hiroyuki Arai, Young-Chan Moon, Duk-Yong Kim,
"Orthogonal-Polarization-Reuse-Antenna(OPRA) Evaluation at Cellular
System" IASP2020, Osaka, Japan, Jan. 2021.
(5) L. Minz, Y. Chi, K. Kwon, M. Yun, Y. Moon, D. Kim, and S. Park,
"MIMO Cellular Network Capacity Enhancement with Multiple Orthogonal
Polarization Reuse" submitted to IEEE Transactions on Antennas and
Propagation.
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