Advanced Science and Technology Letters
Vol.108 (Mechanical Engineering 2015), pp.32-35
http://dx.doi.org/10.14257/astl.2015.108.08
A Study on User Selection in Dual-Polarized Antenna
Systems
Hanho Wang1, Gosan Noh2
1
Sangmyung University, Dept. of Information and Communication Engineering,
Cheonan, Korea
2
Electronics and Telecommuncations Research Institute, 218 Gajeong-ro,
Yuseong-gu, Daejeon, Korea
1
[email protected], [email protected]
Abstract. Dual-polarized antenna (DPA) systems can provide two independent
data transmissions in line-of-sight wireless channel environments. The capacity
of each data stream can be affected by a rotation angle between transmitter and
receiver DPAs and channel gains of vertical and horizontal receiver antennas.
In this paper, we propose a user selection scheme for the DPA system. In the
proposed scheme, the best DPA user is selected based on both the rotation angle
and the channel gains. By using this scheme, the capacity of the DPA system
increases two times when the selection order is three. The selected best user can
even achieve 3 times of capacity when the selection order is six.
Keywords: Dual-Polarization Antenna. User Selection
1
Introduction
Dual-polarization antenna (DPA) consists of a vertical and a horizontal antenna. Two
antennas are perpendicularly comprised. The vertical and horizontal antennas are
physically orthogonal. Each antenna emits polarized electro-magnetic (EM) waves.
EM waves transmitted from both antennas are also orthogonal [1]. Hence, a receiver
can distinguish signals included in the EM waves if the receiver has also DPA.
Different from the conventional multi-input and multi-output (MIMO), DPA is able to
provide two independent data streams without multipath channels by using the
antenna polarization. Accordingly, DPA system is called line-of-sight(LoS) MIMO
system, which can be well applied to indoor small cell with small coverage and LoS
dominant channel [2][3].
Although the DPA can implement the LoS MIMO, there are some technical
difficulties not to degrade the capacity of DPA system. For example, a rotation angle
between a transmitter and its corresponding receiver DPA severely degrades the
capacity of the DPA system. Conventionally, there were researches about minimizing
the rotation angle in DPA system [3][4]. Performance degradation due to the rotation
angle is analyzed in [3]. Interference mitigation is proposed in order to minimize the
effect of the rotation angle on the DPA system capacity [4]. However, those
ISSN: 2287-1233 ASTL
Copyright © 2015 SERSC
Advanced Science and Technology Letters
Vol.108 (Mechanical Engineering 2015)
researches cannot be applied to the LTE system because current LTE modem does not
have functionalities to support the proposed schemes yet.
In this paper, we propose a user selection scheme for the DPA system. In the
proposed scheme, the best DPA user is selected based on both the rotation angle and
the channel gains. By using this scheme, the capacity of the DPA system increases 2
times when the selection order is three. The selected best user can even achieve 4
times of capacity when the selection order is six.
2
System Model
Selected
Rotation Angle: 0.1o
Rotation Angle: 15o
Receivers
Rotation Angle: 60o
Rotation Angle: 100o
Transmitter
Fig. 1. DPA antenna system and rotation angle
System model is illustrated in Fig. 1. In the system model, there are a transmitter
and multiple receivers. Every receiver has a DPA. In Fig. 1, there are four receivers
with different rotation angles. The DPA of the transmitter provides a reference angle
for receivers to measure rotation angles. As illustrated, rotation angles are 0.1, 15, 60,
and 100 degrees. Depending on the rotation angle  , signal-to-interference-andnoise ratio (SINR) which vertical antenna channel of the i-th receiver experiences can
be expressed as [6]:
S IN RV 
i
where H V
i
,V
HV
HV
c o s ( i )
2
i
,V
s in (  i )  N
,
2
i
,H
(1)
0
is the channel gain between the transmitter's vertical antenna and the i-th
receiver's vertical antenna, and H V
Copyright © 2015 SERSC
i
,H
is the channel gain between the transmitter's
33
Advanced Science and Technology Letters
Vol.108 (Mechanical Engineering 2015)
horizontal antenna and the i-th receiver's vertical antenna. N 0 is the background
noise.
There are N receivers. The transmitter selects the best user by using the following
rule:
m ax
S IN R V
 a rg m a x S IN RV
(2)
i
i
As depicted in Fig. 1, each receiver has its own rotation angle. Hence, SINR values of
receivers are different. Using the selection rule in (2), the best SINR receiver is
selected, which will result in selection diversity gain.
3
Simulation and Results
5
Spectral Efficiency (bps/hz)
4.5
4
3.5
3
2.5
2
2.5
3
3.5
4
4.5
Selection Orders
5
5.5
6
Fig. 2. Spectral efficiency improvement v.s. selection orders
Fig. 2 depicts spectral efficiency improvement as the selection order increases.
Selection order is the number of selectable receivers. Focusing on the rotation angle
in (1), SINR value achieves the maximum value when the rotation angle is zero.
Hence, it is more probable that the selected user has smaller rotation angle. Generally,
it is known that the rotation angle is a random variable with the uniform distribution
34
Copyright © 2015 SERSC
Advanced Science and Technology Letters
Vol.108 (Mechanical Engineering 2015)
as a probability density function. Accordingly, the rotation angle decreases as the
selection order increases.
When the selection order is one, the spectral efficiency 1.578 bps/hz. This is a
performance of the random selection. However, as the selection order increases to
three, the spectral efficiency reaches 3.3 bps/hz. This value is more than two times of
the random selection performance. Although DPA system implementation aims at
indoor wireless communication, we can assume six receivers in a office without loss
of generality. In this case, the proposed selection scheme achieves 4.6 bps/hz. This
spectral efficiency is almost three times capacity of that of the random selection.
4
Conclusion
In this paper, a selection diversity scheme was proposed for DPA system, and its
performance was evaluated through computer simulation. Using the selection scheme,
spectral efficiency of a DPA link improves because the selected receiver's rotation
angle gets smaller as the selection order increases. When the selection order is three
and six, the spectral efficiency improves two and three times.
Acknowledgment. This work was supported by the IT R&D programs of
MSIP(Ministry of Science, ICT and Future Planning), Korea [15ZI1110, Research on
Advanced Technologies of Access Network for Traffic Capacity Enhancement]
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