Virtual MIMO Communication Based on D2D Link
Hao Jiang, Shixiang Shao, Jun Sun
Jiangsu Provincial Key Laboratory of Wireless Communication
Nanjing University of Posts and Telecommunications
Nanjing, 210003, P.R. China
Email: jianghao_njut@163.com, {shaosx, sunjun}@njupt.edu.cn
Abstract—Applying MIMO technology into handheld
equipments has always been a widely argued problem due to
their body and power limit. The appearance of device-to-device
(D2D) communication provides one way for solving this problem.
In this paper, we developed the way to construct virtual antenna
array by D2D links and find the method to get diversity gains
using space time block coding between inter cluster
communication. We focused on researching Alamouti coding
which is used in virtual MIMO communication in two different
ways, one is decoding and the other is amplifying. Signal
combination in receiver cluster is also analyzed for increasing the
possibility of decoding.
Keywords—D2D; cooperative communication; virtual MIMO;
Alamouti coding
I. INTRODUCTION
The occurrence of high speed business in next generation
of wireless communication requires rigid design for handheld
equipment. The widely researched MIMO technology is a
promising scheme to enhance the capability of links between
mobile phones and base station. In order to use MIMO
technology, handsets need more than one antenna. Integrating
multiple antennas into mobile terminal is unrealistic because
of the limit on body and power consuming. Some scholars
proposed using virtual antenna array as replacement. In
literature [1], the author researched the performance of virtual
antenna arrays, and compared the difference between
traditional MIMO and distributed MIMO communication.
Literature [2][3] propose space-time block coding (STBC) on
virtual antenna arrays, and [2] mainly mimics Alamouti STBC
to acquire one more information stream at destination through
relay. About relay technology, literature [4] concludes three
different protocols, they are AF(Amplify and Forward) 、
DF(Detect and Forward)、CC(Coded Cooperation), and the
difference is the processing of receiving signals at relays.
Through many years of developing, virtual MIMO technology
has mostly focused on the area of wireless sensing network or
Ad Hoc network. These networks have widely distributed self-
organizing nodes which can be effectively organized into
clusters to transmit signals. According to the situations of
clustering, they can be classified as V-SIMO,V-MISO,V-
MIMO, these concepts are included in literature [5]. Virtual
MIMO technology came up with the problem of resource
allocation. Which tunnel the information exchange between
nodes should be tuned on is important. Paper [6] analyzed
resource reusing among clusters and made comparison to un-
reusing scenario. Virtual antenna technology can nicely deal
with the problem of lacking multiple antennas of terminals. In
practical use, antenna arrays should not be far apart. Large
distance between antennas will cause serious fading which
makes inner cluster communication difficult then leads to bad
performance of whole system. Recently, device-to-device
communication has becoming a hot spot which has the
character of short distance and reliable high data rate. D2D
technology allows short-distance pairs exchange information
directly through authorized channels. It is quite different from
traditional cellar communication which needs base station to
repeat signals thus D2D communication releases the burden of
base station. D2D pairs can reuse frequency of cellar users in
the same cell and the whole throughput of cell together with
frequency efficiency increases. But we have to face the
shortcoming of D2D communication, it constrains application
scenario for its small range feature. In most cases, the
communication pairs are far away from each other. Blue-tooth
and infra technology are strong competers in short range
communication while they work in un-authorized band. In this
article, we take advantage of the short range characteristic by
constructing virtual antenna arrays using D2D links. The
author invent a STBC method for 2×2 antenna system in paper
[8] which is known as Alamouti STBC. Literature [9] provide
AF based space time coding method in which the assistant
equipments do not need to decode the signal and virtual
antenna arrays can still be organized even if decoding fails.
We develope the virtual MIMO communication based on D2D
links and analyzed two situations different in deals at assistant
equipment according to whether assistant user can decode
signal. The enhancement at destination cluster is one of our
researching point.
The remaining of this paper is organized as follows.
Section II gives system model for D2D link based virtual
MIMO communication. Amplifying and decoding based
virtual MIMO communication methods are described in
section III. In Section IV, we analyzed the performance of our
method and simulated. We conclude in part V.
II. S
YSTEM MODEL
Proposing there exists a user S want to talk to user D.
When the base station require them to try building direct link
for communication, they find the signal is too weak to build
D2D link because S and D are far away. Then S and D can
request users surrounding them to provide help. They form
antenna arrays which can enhance the connectivity between S
and D. N surrounding free equipments around S represented
by S1, S2…SN construct transmitting cluster (T-cluster) and
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