Impact of Untrusted Relay on Physical Layer Security in Non‑Orthogonal Multiple Access Networks

Vol.:(0123456789)

Wireless Personal Communications

https://doi.org/10.1007/s11277-019-06219-y

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Impact of Untrusted Relay on Physical Layer Security

in Non‑Orthogonal Multiple Access Networks

Dinh‑Thuan Do1,2  · Minh‑Sang Van Nguyen3

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Abstract

In this study, the wireless sensor network is investigated in scenario of untrusted relay

required to user at far distance. In particular, an untrusted relay assists long distance trans￾mission in  situation of non-existence of the direct link between source and destination.

This paper employs non-orthogonal multiple access (NOMA) scheme to serve large num￾ber of users at diferent allocated power levels to adapt secure criteria. Specifcally , to

evaluate the security performance we frst examine the secure outage probability (SOP)

and then strictly positive secrecy capacity (SPSC) is studied. To further characterize the

trade-of between system security and other controlling coefcients, we then investigate the

impacts of power allocation factors and power levels of the eavesdropper. In order to fnd

tractable expressions to provide additional insights in term of the performance evaluation,

the asymptotic expressions regarding both SOP and SPSC are performed in high signal-to￾noise ratio (SNR) region. In addition, secure performance of considered NOMA network

is compared in two modes related to untrusted relay, including Amplify-and-Forward and

Decode-and-Forward mode. Finally, simulation results are presented to corroborate the

proposed methodology.

Keywords Strictly positive secrecy capacity · Non-orthogonal multiple access · Jamming

signal · Secure outage probability · Physical layer security

* Dinh-Thuan Do

[email protected]

Minh-Sang Van Nguyen

[email protected]

1 Wireless Communications Research Group, Ton Duc Thang University, Ho Chi Minh City,

Vietnam

2 Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City,

Vietnam

3 Faculty of Electronics Technology, Industrial University of Ho Chi Minh City, Ho Chi Minh City,

Vietnam

D.-T. Do, M.-S. Van Nguyen

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1 Introduction

To familiarize substantially growth regarding the throughput in the ffth generation (5G)

networks, it required the unprecedented evolution of new Internet-enabled smart devices,

and related applications and services. Considering several techniques to improve the spec￾tral efciency, key architectures such as novel multiple access (MA) techniques, cognitive

radio, heterogeneous networks, millimeter wave communications, multiple-input multiple￾output (MIMO) for large-scale networks can be implemented to upgrade current networks.

Regarding MA schemes including orthogonal multiple access (OMA) and non-orthogonal

multiple access (NOMA), these considered main categories are deployed to primarily pro￾vide multiple access methodology. In MA, it is introduced that signals distinguishing a

explicit resource block can be employed by multiple users [1, 2]. More specifcally, code￾domain NOMA and power-domain NOMA are classifed for NOMA upon exploring the

multiplexing gain from the diferent domains [3].

Lately, cooperative jamming and artifcial noise (AN) assisted model to improve physi￾cal layer security (PLS), even if the the legitimate receivers have worse channel conditions

than the eavesdroppers [4, 5]. Goel and Negi in [6] proposed a technique by generating

AN at the transmitter to decrease the eavesdroppers reception. In principle, improving the

security by producing AN at the transmitter is diferent scheme compared with a detrimen￾tal efect of noise and interference, because it destroys the channel conditions of eaves￾droppers without disturbing those of the legitimate receivers. The perfect and imperfect

channel state information (CSI) at both the transmitter and receiver are examined in an

AN based multi-antenna assisted secure transmission scheme afected by colluding eaves￾droppers [7]. As a further development, the authors in [8] using both beamforming and

sectoring techniques to achieve the secrecy enhancement in wireless Ad Hoc networks.

Specially, the authors in [8–12] presented an efective technique to confuse the eavesdrop￾per by deploying AN at the legitimate transmitter. As an efective method to enhance the

system security, the authors in [9] have also been performed cooperative full-duplex relay.

In [7], a relay networks can be able to largely improve the physical layer security through

using AN-aided strategy. In other trends, many secure transmission strategies are intro￾duced, for example cooperative beamforming (CB) [8] and cooperative jamming (CJ) [9]

by conveying the benefts of AN assistance in cooperation with relaying transmission. It

can be realized the randomness and time-varying nature of the wireless channels to sup￾port for network security without deploying any encryption algorithm, PLS is proposed in

both information security and wireless communications [13]. Zhang et al. proved that the

secrecy sum rate performance of NOMA better than the one of the conventional OMA in

scenario of the security performance of single-input-single-output (SISO) NOMA system

[14]. Qin et al. [15] derived new secrecy outage probability (SOP) in forms of exact and

asymptotic expressions to explore physical channel-assisted security of NOMA networks

in large-scale networks wherein spatially randomly location deployment for both NOMA

users and eavesdroppers. Furthermore, the authors in [16] presented the exact and asymp￾totic expressions for SOP in term of the secrecy performance in case of NOMA employ￾ing multiple antenna and artifcial noise as well. To improve the secrecy performance

of a MIMO system, optimal antenna selection (OAS) and suboptimal antenna selection

(SAS) schemes are proposed which based on whether the base station has the global chan￾nel state information (CSI) of both the main and wiretap channels [17], and those perfor￾mance were compared with the outdated space time transmission (STT) scheme. The the

exact and asymptotic SOP in closed-form expressions is derived for an underlay MIMO