
Opportunistic Full-Duplex Relay Selection for
Decode-and-Forward Cooperative Networks over
Rayleigh Fading Channels
Bin Zhong
1
, Dandan Zhang
1
, Zhongshan Zhang
1,2
*, Zhengang Pan
3
, Keping Long
1
and Athanasios V. Vasilakos
4
1
Technology Research Center for Convergence Networks and Ubiquitous Services
University of Science and Technology Beijing (USTB), Beijing, China 100083
2
National Mobile Communications Research Laboratory, Southeast University
3
Green Communication Research Center (GCRC) of China Mobile Research Institute (CMRI)
4
Department of Computer and Telecommunications Engineering, University of Western Macedonia
Email: {zhongbin-1982,zhangdandan0310}@163.com; {zhangzs,longkeping}@ustb.edu.cn;
panzhengang@chinamobile.com; vasilako@ath.forthnet.gr
Abstract—The performance analysis of optimal relay decode-
and-forward (DF) selection for both the full-duplex (FD) and
half-duplex (HD) relaying modes is studied, with some important
factors such as the distributions of the received signal-to-noise
ratio (SNR), the outage probability and the average channel
capacity, etc., being taken into account. Different from the
conventional relay selection schemes, the trade-off between the
FD and HD modes is studied, with the former suffering from the
impact of residual self-interference while the latter consuming
more channel resources than the former by allocating two
orthogonal channels for transmission and reception. The optimal
power allocation (OPA) subject to individual power constrains
(IPC) and sum power constrains (SPC) are also analyzed in
the proposed FD scheme. In particular, the exact closed-form
expressions for outage probability of the proposed FD relay
selection scheme over independent and identically distributed
(i.i.d.) Rayleigh fading channels are derived in this paper, with
the validity of the proposed analysis being proven by simulation.
It is also shown that the proposed FD scheme outperforms the
HD mode in terms of average channel capacity by about 33.1%,
provided that the self-interference can be successfully suppressed
below the noise power level.
I. INTRODUCTION
Since modern communication networks must deliver ever
increasing data rates, the spectral efficiency of the wireless
networks has to be further improved. Besides, customers also
require the communication networks to provide an ever ex-
tending radio coverage to facilitate a seamless wireless service.
Cooperative communications have been identified as promis-
ing solutions for combating the shadowing effect, extending
the n etwork coverage and increasing the throughput [1]–[3].
Besides, more benefits, such as an expanded coverage, a b etter
immunity against signal fading and a more system-wide power
saving [4]–[7], can be brought by adopting multiple relays.
In a multi-relay cooperative system, since an orthogonal
channel allocation (e.g., in carrier frequencies, time slots or
codes) among relays must be performed to mitigate the inter-
relay interference, the cost of spectrum utilization penalty may
even deteriorate the benefits brought by using multiple relays
if the number of relay s becomes large. In order to mitigate
the aforementio ned disadvantages, the relay selection with the
feedback channel state information (CSI) is regarded as one of
the most attractive methods to solve the complicated problem
of inter-relay interference mitigation. Furthermore, a highly
energy-efficient relay selection scheme is proposed in [8] for
cooperative multicast transmission.
Selecting the optimal relay to forward data is proven to be
an ideal way to effectively balance the achievable diversity
order and the spectral efficiency improvement [9], [10]. There
are many related studies have been focused on half-duplex
(HD) relaying mode [11], [12]. The full-duplex (FD) relaying,
on the other hand, allows concurrent transmission and recep-
tion of a communication device in a single time/frequency
channel [13]. Although full-duplex node receives and transmits
on the same channel simultaneously and thus utilizes the spec-
trum resources more efficiently, as a downside the full-duplex
node is subject to self-interference due to the large power
difference between the self-interference created by a device’s
own wireless transmissions and the received signal of interest
coming from a remote transmitting antenna. A sign ifican t
improvement of spectral efficiency than the conventio nal HD
mode can be obtained by the FD scheme if the self-interference
can be effectively suppressed [14].
Since most o f the existing works consider only a single
FD relay in the cooperative network [15], [16], relay selection
in the presence of multiple FD relays is still a challenging
task. Besides, the transmitted power of relay may significantly
degrade the performance of FD cooperative networks due to
the impact of self-interference. The optimal power allocation
(OPA) is thus critical to optimizing the performance of FD co-
operative networks. By and large, power allocation techniques
in communication systems can be developed subject to the
following two constraints, i.e., the individual power constrains
(IPC) and the sum power constrains (SPC) [17], [18]. In
IEEE ICC 2014 - Wireless Communications Symposium
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