Regular paper
On the study of cognitive two-way relaying using a denoise-and-forward
relay
Ruifeng Gao
a,c
, Xiaodong Ji
a,b
, Zhihua Bao
a,b,
⇑
a
School of Electronics and Information, Nantong University, Nantong 226019, China
b
Nantong Research Institute for Advanced Communication Technologies, Nantong 226019, China
c
School of Transportation, Nantong University, Nantong 226019, China
article info
Article history:
Received 23 January 2017
Accepted 6 July 2017
Keywords:
Two-way relay
Cognitive radio
Denoise-and-forward
Operating region
abstract
In this paper, we consider a cognitive cooperative wireless system consisting of two primary users, a cog-
nitive base station (CBS) and a secondary user. A cognitive two-way relaying (CTWR) scheme is proposed,
where the secondary user tries to assist the primary users to meet their target quality of service (QoS) by
acting as a cognitive two-way relay, when the direct link of the two primary users cannot meet the target
QoS. As a return, the primary network shares its transmission time-slot with the secondary user. First, the
system outage probabilities of traditional direct transmission and CTWR scheme are analyzed, giving
both the exact and approximated expressions. Second, a transmission time-slot splitting algorithm
between the primary and secondary users is proposed. Third, the ergodic capacity of the secondary user
under the CTWR scheme is examined. Finally, simulation results show that the proposed scheme cannot
only help the primary users to meet their target QoS, but also improve the communication opportunities
of the secondary user.
Ó 2017 Elsevier GmbH. All rights reserved.
1. Introduction
With the rapid growth of wireless applications, requirements
for data transmission and scenario deployment are increasing
rapidly as well. However, due to the vulnerability of wireless radio
link, data transmission suffers severe fading and path loss effects.
Cooperative technology with relay nodes, can effectively improve
the quality of wireless transmissions including throughput, relia-
bility, coverage, etc. [1]. On the other hand, the demand of wireless
spectrum is also increasing rapidly. Cognitive radio is considered as
a promising technology to improve the efficiency of spectrum uti-
lization that can dynamically access a wireless channel by perceiv-
ing the wireless spectrum environment [2,3]. Thus, using
cooperative technology in cognitive radio environment is consid-
ered to be a feasible solution to improving both of the spectrum
efficiency and transmission reliability [4–6].
Two-way relaying, where two users exchange information with
the help of a relay can improve the spectrum efficiency and the
throughput by reducing the numbers of channel uses for one round
of communication between two source nodes [7,8]. Recently, using
two-way relay in cognitive radio environment has attracted lots of
attention. The cognitive decode-and-forward(DF) two-way relay-
ing system considering the interference between the primary and
secondary users are studied in [9].In[10], a transmission protocol
is proposed for cognitive bidirectional relay transmission using an
amplify-and-forward(AF) relay. In [11], relay beamforming perfor-
mance is studied in cognitive two-way relay system with imperfect
channel information, giving the achievable rates for reliable com-
munications. The authors of [12] present a robust precoder design
for two-way relaying in cognitive radio networks. It should be
noted that a new relaying protocol called denoise-and-forward
(DNF) is considered as a potential method for spectrum efficiency
enhancement [13,14]. The DNF relay detects and re-modulates
the XOR of two users’ transmitted bits at the end of the first
time-slot and forwards the XOR bits at the second time-slot
[13–15].In[16], it shows that DNF protocol can result in more
throughput than that of AF and DF protocols under low signal–
noise-ratio(SNR) regime. Although there are many works investi-
gating outage performance of two-way relay networks using
various relaying protocols. However, most of them consider either
AF or DF protocol [8,9,17,18]. In our paper, we consider a DNF pro-
tocol based network, which is completely different from the DF and
AF protocols, and not well studied in the literature. To our best
knowledge, outage analysis of two-way DNF relaying networks
has not been studied and deserves a through investigation.
http://dx.doi.org/10.1016/j.aeue.2017.07.006
1434-8411/Ó 2017 Elsevier GmbH. All rights reserved.
⇑
Corresponding author at: School of Electronics and Information, Nantong
University, Nantong 226019, China.
E-mail addresses: grf@ntu.edu.cn (R. Gao), jxd@ntu.edu.cn (X. Ji), bao.zh@ntu.
edu.cn (Z. Bao).
Int. J. Electron. Commun. (AEÜ) 81 (2017) 150–157
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International Journal of Electronics and
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