Outage Probability Analysis of Full-Duplex
Regenerative Relaying over Generalized
Asymmetric Fading Channels
Mulugeta K. Fikadu
1
, Paschalis C. Sofotasios
1,2
, Mikko Valkama
1
,QimeiCui
3
,SamiMuhaidat
4,5
,
and George K. Karagiannidis
2,4
1
Department of Electronics and Communications Engineering, Tampere University of Technology, 33101 Tampere, Finland.
e-mail: {mulugeta.fikadu; paschalis.sofotasios; mikko.e.valkama}@tut.fi
2
Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
e-mail: geokarag@auth.gr
3
Wireless Technology Innovation Institute, Beijing University of Posts and Telecommunications, 100876 Beijing, China.
e-mail: cuiqimei@bupt.edu.cn
4
Department of Electrical and Computer Engineering, Khalifa University, PO Box 127788, Abu Dhabi, United Arab Emirates.
5
Department of Electronic Engineering, University of Surrey, GU2 7XH, Guildford, United Kingdom.
e-mail: muhaidat@ieee.org
Abstract—This work is devoted to the outage probability
analysis of full-duplex (FD) regenerative relay systems over
multipath fading channels. Unlike the majority of analyses that
assume basic symmetric fading conditions, the present work
considers asymmetric generalized fading conditions, which are
more realistic in practical communications scenarios. To this
end, we assume that the source-relay path is subject to κ − μ
multipath fading conditions, that can also account for line-
of-sight communications, whereas the source-to-destination and
relay-to-destination paths are subject to η−μ fading conditions
that typically hold for non-line-of-sight communications. Novel
analytic expressions are derived for the outage probability (OP)
of the considered FD as well as for the corresponding half-
duplex (HD) relay case for comparisons. These expressions are
given in closed-form and have a tractable algebraic representation
which renders them convenient to handle both analytically and
numerically. Based on this, they are subsequently employed in
analyzing the corresponding performance for different commu-
nication scenarios. It is shown that the OP of the FD relay
system is highly dependent upon the severity of fading and that
its performance outperforms significantly the corresponding HD
performance as the spectral efficiency increases.
I. INTRODUCTION
Cooperative communications have attracted significant in-
terest over the past decade due to their potential to expand
cellular network coverage, increasing channel capacity and
reduce power consumption of wireless devices [1]. Tradi-
tionally, relay systems are assumed to operate in half-duplex
(HD) mode where the relay receives and transmits on orthog-
onal channels [2]–[8] and the references therein. However,
although HD architectures are considered relatively simpler
in terms of system design and implementation requirements,
they also suffer by inherent spectral efficiency loss. On the
contrary, full-duplex relaying has been proposed as an effective
alternative architecture that is capable of overcoming this
critical inefficiency by allowing relay(s) to receive and transmit
simultaneously at the same frequency band, see e.g. [9] and
the references therein.
However, full-duplex communications are practically sus-
ceptible to the inherent relay self-interference (RSI) due to
the concurrent transmission and reception. Yet, recent studies
have shown that FD relaying strategies are feasible even in the
presence of high self-interference levels [10]. Motivated by
this, the authors in [11] derived closed-form expressions for
the outage probability (OP) over Rayleigh fading channels by
considering the relay self-interference. Likewise, the authors
in [12] analyzed the performance of full-duplex block Markov
relaying with self-interference at the relay over independent
but non-identically distributed Nakagami−m fading channels.
A comprehensive OP analysis in a three-terminal full-duplex
relay system for a selective decode-and-forward (DF) pro-
tocol with RSI was studied in [13] whereas the authors in
[14] proposed hybrid techniques that switch opportunistically
between FD and HD relaying modes in both DF and amplify-
and-forward (AF) systems.
Nevertheless, all reported investigations on FD relaying as-
sume information transmission over symmetric multipath fad-
ing channels, i.e., that the source-relay and relay-destination
links undergo the same fading conditions. However, this
assumption is rather simplistic since in realistic communi-
cation scenarios, different wireless paths are subject to non
identical fading channels while they experience generalized
fading conditions [15]–[18] and the references therein. For
example, communication in one path might be line of sight
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