Đánh giá chế độ truyền lựa chọn nút chuyển tiếp thu thập năng lượng vô tuyến trong mạng vô tuyến chuyển tiếp song công
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
92
INVESTIGATION ON HARVESTED ENERGY-ASSISTED RELAY
SELECTION MODES IN WIRELESS POWERED FULL-DUPLEX
RELAYING NETWORKS
ĐÁNH GIÁ CHẾ ĐỘ TRUYỀN LỰA CHỌN NÚT CHUYỂN TIẾP
THU THẬP NĂNG LƯỢNG VÔ TUYẾN TRONG MẠNG VÔ TUYẾN
CHUYỂN TIẾP SONG CÔNG
Pham Thi My Linh1, Nguyen Thai Anh1, Do Dinh Thuan2, Tran Thu Ha1
1Univesity of Technology and Education, HCMC, Vietnam
2Eatern International University, Binh Duong, Vietnam
Received 28/10/2016, Peer reviewed 20/01/2017, Accepted for publication 05/3/2017
ABSTRACT
In this paper, the authors investigate relay selection for decode-and-forward (DF)
Full-duplex (FD) based wireless energy harvesting relaying networks. Considering
time-switching based relaying (TSR) protocol, this investigation is concerned with the
performance of maximum harvested energy relay selection (MHE-RS) scheme. In particular,
this work analyzes the system performance in terms of outage probability (OP) and
throughput over Rayleigh fading channels. As important achievement, the integral-form for
exact expression and closed-form for approximate expression are derived. Finally, these
analytical expressions are validated by the Monte-Carlo simulation.
Keywords: Decode and forward; energy harvesting; time switching based relaying; relay
selection.
TÓM TẮT
Trong bài báo này, chúng tôi đánh giá mạng vô tuyến chuyển tiếp lựa chọn nút chuyên
tiếp song công (FD) áp dụng kỹ thuật giải mã và chuyển tiếp (DF) có khả năng thu thập năng
lượng vô tuyến. Xem xét giao thức chuyển tiếp dựa trên chuyển đổi thời gian, bài báo này đề
cập giao thức lựa chọn nút chuyển tiếp thu thập năng lượng cực đại MHE-RS. Cụ thể, bài báo
phân tích chất lượng hệ thống liên quan xác suất dừng và thông lượng cho mạng vô tuyến
dùng các kênh truyền fading Rayleigh. Kết quả quan trọng là biểu thức chính xác dạng tích
phân và biểu thức tính gần đúng đã được chứng minh. Cuối cùng, các biểu thức phân tích này
được kiểm chứng qua mô phỏng Monte-Carlo.
Từ khóa: giải mã và chuyển tiếp; thu thập năng lượng; chuyển tiếp dựa trên thay đổi thời
gian thu năng lượng; lựa chọn nút chuyển tiếp.
this technique can provides new power
1.
INTRODUCTION
supply schemes for wireless communication
network and solve problem of energy
assumption efficient in sensor node.
Normally, the data transmission mode
operates in one-way in wireless network. The
performances of relay networks will be
improved by full duplex transfer [2,3]. In
addition, the RF signal can carry both energy
and information which leads to deploy
simultaneous wireless information and power
The wireless communication network
has
a
limited lifetime and battery
replacement or charging is a way to keep
continuing operation in such network. This
takes a lot of time, inconvenient, risky or
sometime unfeasible. In recent years, there
are many works related to energy harvesting
from the natural environment, such as sun,
solar, wind, vibration and so on [1]. In fact,
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
93
transfer (SWIPT) [5,6]. In hardware
In this scenario, it is assumed that source
implementation, the circuit design aims to node and destination node are equipped with
combine information processing and power one antenna and relay node is equipped with
transfer at the same time on a unit. two antennas. The self-interference is caused
Furthermore, SWIPT using relays has been by the
FD
mode.
The
residual
known as great idea to expand coverage and self-interference channels at relay node Ri is
prolong lifetime of wireless network that also denoted by fi.
a way to improving quality of service.
It is assumed that the direct link between
In this paper, we are concerned with
relay selection system and using DF protocol.
In this system, the transmitted signal
transfers to relays from source, after that the
relays which assists system compare and
choose a best relay to forward to destination.
sources does not exist due to the shadowing
effect.
Relay model: To perform capability of
harvested energy, in this FD relaying, the
relay only has limited power supply, and
relies on external charging through
harvesting energy from the source
transmission [6,7].
The contributions of this paper are list as
follow
i) Proposing a relay selection protocol,
which can select an appropriate relay to assist
2.2. Relay Selection Protocol
Relay selection (RS) is an effective
method to enhance the performance of
multi-relay communication system with a
low complexity, in which only one relay is
selected among all the relay candidates [5].
In this paper, we proposes RS scheme for
one-way FD EH relaying network, namely,
maximum harvested energy relay selection
(MHE-RS). In particular, the relay with the
largest harvested energy is choosed to
assistance transmit information to destination
node. The index of the selected relay is given
by
the
transmission
between
a
given
source-destination pair considering
dual-hop DF relaying network with multiple
wireless energy harvesting relays.
a
ii) Deriving the analytical expression
for outage probability and throughput, also
obtaining the closed-form expression of their
approximation in high SNR case. Based on
the analytical expressions, the optimal
throughput and energy harvesting time are
discussed in detail.
The rest of this paper is organised as
follows. In Section 2, the system model and
proposed relay selection protocols are
presented. In Section 3, we formulate the
expressions for outage probability and
throughput of system. In Section 4, numerical
results verify derived analytical expressions.
Finally, Section 5 concludes the paper.
b arg max E
(1)
i
i1,...,N
2. SYSTEM MODEL
2.1. Relay selection network topology
In this model, we investigate a one-way
FD EH relay selection network with DF
protocol as illustrated in Fig. 1.The system
consists of one source node and one
destination node, denoted by SandD,
respectively and N relays, denoted by
Ri ,i 1,..., N
.
Fig.1. System model
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
94
At destination node, the received signal
2.3. Analysing system performance
at D, yd
t
, is expressed as
In energy harvesting phase, source S
transmits power to assistance node R via RF
signal. Therefore, the received signal at R is
described as
pr
i
y t
d
g x t n t
(7)
d
i
r
i
m
d2i
where nd
t
is the AWGN at D with
ps
(2)
yi
h x t n t
s
i
ri
zero-mean and variance of N0.
m
d1i
According to (5) and applying some
steps in manipulation, the instantaneous
received SINR of S → Rhop is written as
in which i 1,..., N is the number of relay
node.
2
Hence, we can calculate the total
harvested energy during the EH stage as
following [3]
s hi
si,r
(8)
s hi fr 2 1
2
i
ps
hi 2
T
Similarly, based on (7) the instantaneous
(3)
Ei
(3)
is the portion signal power
1
m
d1i
received SNR of R → D hop is expressed as
2
2
ri,d
s hi gi
where
0
(9)
splitting to scavenge energy.
where s ps N0
As in [3, 4], we assume that the energy
harvested during the energy harvesting phase
is stored in a super-capacitor and then fully
consumed by the relay to forward the source
signal to the destination. Hence, the relay
transmit power can be computed as .
To look insights system performance, we
evaluate the special case. In high SNR, i.e.
s , the expressions in (8) and (9) can be
re-expressed respectively as below
1
s,sr,i
(10)
(11)
2
fi
Ei
1
ps
2
pr
hi
(4)
i
m
2
2
s ,i
T
d1i
And
r,d
s hi gi
Here, we denoted the value
Based on DF relaying procotol, the
end-to-end SINR of the system is determined as
In the information processing stage, the
sources, S, transmits its respective symbol
ei2e min si,r , ri,d
(12)
xs
t
to Ri. Simultaneously, Ri broadcasts
3. PERFORMANCE ANALYSIS
xr
t
another symbol
to the destination D.
i
In this section, we will study the
performance of the considered schemes in
terms of outage probability and throughput
over Rayleigh fading channels.
Therefore, the received signal at Ri is
ps
yr t
h x t
s
i
i
m
d1i
(5)
Through this paper, we denote “OP”
stands for outage probability and “ ” for
pr fi xr t n
t
ri
i
throughput of the system, PDF is probability
density function and CDF is cumulative
distribution function.
In DF relaying protocol, the transmited
symbol atRiis denoted by
x
t
,and is the
ri
3.1. Outage Probability Analysis
code translation of the prior received signal
at relay, given as
The outage probability of the system is
defined as the probability that the system
SINR is below a threshold SNR, 0 . In
x t x t
s
(6)
r
i
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
95
two-hop DF relaying protocol, the mistake of
The first element in (18) is
one of the two hops leads to the outage event
of the transmission. Thus, the system’s
outage probability can be mathematically
formulated as
1
1
2
s
OP
Pr
f
1 F
fi
2
i
1
0
0
(19)
1
exp
f 0
OP Pr b
0
(13)
e2e
and OP2 can be expressed as below
Subtituting (12) into (13), the outage can
be re-written as
N
N
k1
s
OP2
1 2
1
k
OP Pr min b
,
rb,d
0
k1
s,r
(20)
k
0
k
0
Pr b
0 Pr b
0
,
sb,r
0
(14)
2
r,d
r,d
1
sgh
sgh
OP OP2
1
Finally, substituting(19) and (20) into
(18) to results in the proposition 2 is derived.
Interestingly, by substituting (3) into (1),
the best selected relay index is expressed as
3.2. Throughput Analysis
2
b arg max hi
(15)
i1,...,N
In delay- constrained transmission mode,
the source transmits information at a fixed
rate and outage probability plays a pivotal
role in the throughput. Given that source S
transmit information with fixed rates Rc
Proposition 1: The outage probability of
MHE-RS scheme is
N
N
k
k1
0
sg h
k
k
k1
OPMHERS
1
1 S
,
h
(16)
bits/sec/Hz, respectively, then we derive the
throughput as below
0
1
1
k
exp
S
,
0 f
sg s f h
More specifically, the throughput of the
relay selection and full duplex energy
harvesting relaying system is calculated as
S u,v
exp u x vx dx
Where
,
s
0
MHE-RS 1
1OP
MHE-RS
R
(21)
Proof: see in appendix A.
c
Proposition 2: In high SNR the outage
probability of MHE RS scheme is given as
Especially, in high SNR, the desired
throughput is expressed as
1
f 0
s
OPM HERS 1 2 1 exp
s
s
M HE-RS 1
1OP
R
c
(22)
MHE-RS
(17)
N
The optimal time switching could be
calculated by solving the optimization
problem as below
N
k
k
0
k
0
k1
1
1
2
sgh
sgh
k1
Proof: In high SNR, with independence
opt
MHE-RS
argmax
(23)
MHE-RS
s
s,r
s
r,d
of
and
the outage expression
01
in (13) can be derived as
It is worth noting that finding optimal
coefficient is hard problem. Fortunately,
these optimal time switching fractions can be
found in simulation section.
s
s ,b
OP
1 1 Pr
0
s,r
OP s
1
(18)
4. NUMERICAL RESULTS AND
DISCUSSION
1 Pr
0
s ,b
r,d
In this section, we present numerical
results in order to illustrate the solution to the
OP2 s
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
96
2
throughput optimization issues of the energy
harvesting enabled relaying scheme in the
proposed RS protocols. Through numerical
method, the optimal throughput in terms of
energy harvesting time ratio in the TSR
scheme is evaluated.In these simulations, we
setup the transmission power s 25 (dB),
the distance corresponds each hop is
normalized as d1 d2 1 , path loss factor
m 3 , the energy harvesting efficiency
Exact analysis
1.8
1.6
1.4
1.2
1
Analysis: high SNR
Monte-Carlo simulation
0.8
0.6
0.4
0.2
0
N = 2, 4, 10
0.9 , the fixed transmission rate of the
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
source Rc 2(bps) , hence 0 22 1 3. In
all simulations, h and g are denoted as
the mean values of the exponential random
Energy harvesting ratio ()
Fig 3. Throughput vesus energy harvesting
time ratio.
2
2
variables
set to h d1m and
and
, respectively, are
hi
gi
g d2m
.
4.2. Performance of the system versus the
number of the relay
4.1. Impact of energy harvesting time ratio
For evaluation of impacts of the
number of the relay on the system
performance, the throughput is proved that
depend on the number of the relay. The
more number of the relay, the outage
probability will be improved as in Fig. 4,
while the higher number of relay leads to
The outage probability depends on the
energy harvesting time ratio as illustration in
Fig. 3. As can be seen clearly that when the
time use to energy harvesting α=0.4 to
α =0.7, it results in outage probability come
to zero.
In parallel, the throughput depends on higher throughput as in Fig. 5. It is
the energy harvesting time ratio. When the confirmed that the outage performance and
outage probability is considered in high rate the throughput of both exact analysis and
that means the quantity of throughput is analysis with high SNR are the same.
reduced.
100
5. CONCLUSION
Exact analysis
Analysis: high SNR
In this paper, the authors have
Monte-Carlo simulation
proposed a relay selection protocol for
FD-DF relaying network with SWIPT,
N = 2, 4, 10
10-1
where one of candidate constrained relay
node is selected to forward the source
signal to the destination. In order to
10-2
determine the achievable throughput,
analytical expressions for the outage
probability and the optimal value of
energy harvesting time in TSR protocol
can be found by simulation. The
simulation results show that, the more
relays support, the more throughput can be
obtained. Besides, the quality of relaying
system also depends on proposed relay
selection scheme.
10-3
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Energy harvesting ratio ()
Fig2. Outage probability vesus energy
harvesting time ratio. With number of
N 2,4,10
assistant relay
, mean of self
f 15
interference channel
(dB)
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
97
100
1.8
Exact analysis
Analysis: high SNR
Exact analysis
1.6
1.4
1.2
Analysis: high SNR
1
0.8
0.6
0.4
0.2
0
10-1
s = 10, 15, 20 (dB)
s = 20, 15, 10 (dB)
10-2
5
10
15
20
25
5
10
15
20
25
N
N
Fig 4. Outage probability of the system versus
Fig 5. Throughput of the system versus the
the number of the relay
0.2
,
f 15
(dB)
number of the relay
0.2 f 15
(dB)
,
REFERENCES
[1] Z. Ding, S. M. Perlaza, I. Esnaola, and H. V. Poor, Power allocation strategies in energy
harvesting wireless cooperative networks, IEEE Trans. Wireless Commun., vol. 13, no.
2, pp. 846–860, 2014.
[2] B. Debaillie et al., “Analog/RF solutions enabling compact full-duplexradios,” IEEE J.
Sel. Areas Commun., vol. 32, no. 9, pp. 1662-1673,Sept. 2014.
[3] Z. Zhang, X. Chai, K. Long, A. V. Vasilakos, and L. Hanzo, “Full duplex techniques for
5G networks: Self-interference cancellation, protocol design, and relay selection,” IEEE
Commun. Mag., vol. 53, no. 5, pp.128-137, May 2015.
[4] A. A. Nasir et al, “Relaying protocols for wireless energy harvesting and information
processing,” IEEE Trans. Wireless Commun., vol. 12, no. 7, pp. 3622–3636, Jul. 2013.
[5] I. Krikidis, J. Thompson, S. McLaughlin, and N. Goertz, “Amplify-and-forward with
partial relay selection,” IEEE Commun. Lett., vol. 12, no. 4, pp. 235–237, Apr. 2008.
[6] S. Hong and G. Caire, “Virtual full-duplex relaying with half-duplex relays,” IEEE
Trans. Inf. Theory, vol. 61, no. 9, pp. 4700-4720, Sep. 2015.
[7] Caijun Zhong, Himal A. Suraweera, Gan Zheng, Ioannis Krikidis, and Zhaoyang Zhang.
"Wireless information and power transfer with full duplex relaying.", IEEE Transactions
on Communications, vol.62, no. 10 (2014): 3447-3461.
APPENDIX A
2
Based on relay selection scheme in (15), CDF of
channel is given as
hb
N
N
k
kx
k1
(24)
(25)
f h x
2
1
exp
k
b
h
h
k1
where the value of first term in (14) is determined as
0
s x
2
2
OP Pr s hb gb 0
F
f
x dx
2
2
1
gb
hb
0
Journal of Technical Education Science No.44A (10/2017)
Ho Chi Minh City University of Technology and Education
98
2
Substituting the PDF of
2 in (24) and CDF of
into (25). The OP is re-expressed as
(26)
hb
gb
N
N
0
k
kx
k1
OP 1
1
exp
dx
k
1
h
sg x h
k1
0
0
1
1
s hb
2
2
OP Pr
g
2 , fi
2
b
2
0
s hb
(27)
(28)
0 s
0
0
sg x
1
1
1 Fg
f h x dx
1 Fg
1 F
f
hb
x dx
2
2
2
2
2
fi
b
b
i
sg x
0 s x
0
0 s
Finally, the second term in (14) is determined as
0 s
N
N
0
k
kx
1
k1
OP
1
exp
dx exp
k
2
h
h sg x
0 f
k1
0
N
N
k
k1
0
x sg h
k
1
kx
k1
1
exp
dx
h
x
s f
0 s
Corresponding Author:
Do Dinh Thuan
Eastern International University, Vietnam
Email: [email protected]
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