Abstract
In this paper, an Internet-of-Things (IoT) system containing a relay selection is studied as employing an emerging multiple access scheme, namely non-orthogonal multiple access (NOMA). This paper proposes a new scheme to consider secure performance, to be called relay selection NOMA (RS-NOMA). In particular, we consider metrics to evaluate secure performance in such an RS-NOMA system where a base station (master node in IoT) sends confidential messages to two main sensors (so-called NOMA users) under the influence of an external eavesdropper. In the proposed IoT scheme, both two NOMA sensors and an illegal sensor are served with different levels of allocated power at the base station. It is noticed that such RS-NOMA operates in two hop transmission of the relaying system. We formulate the closed-form expressions of secure outage probability (SOP) and the strictly positive secure capacity (SPSC) to examine the secrecy performance under controlling setting parameters such as transmit signal-to-noise ratio (SNR), the number of selected relays, channel gains, and threshold rates. The different performance is illustrated as performing comparisons between NOMA and orthogonal multiple access (OMA). Finally, the advantage of NOMA in secure performance over orthogonal multiple access (OMA) is confirmed both analytically and numerically.
Highlights
Any eavesdropper is able to disturb the signal due to the broadcasting environment of wireless communication
We analytically prove that the relay selection provides improved secure performance at higher number of relay for RS-non-orthogonal multiple access (NOMA)
Under impact of eavesdropper based on two system metrics including secure outage probability (SOP) and strictly positive secure capacity (SPSC). We investigate these metrics by considering the effects of transmit signal-to-noise ratio (SNR), fixed power allocation factors, the number of relays, channel gains
Summary
Any eavesdropper is able to disturb the signal due to the broadcasting environment of wireless communication. At the application layer (i.e., highest layer), encryption methodology using cryptography is conventionally implemented to assurance the secure information transmission. To tackle with situation of speedy growth of computer networks, these procedures and secure keys become ineffective ways, especially in increasing computing capability [1]. Physical layer security (PLS) is an effective way to fight eavesdropping and diminish the overhearing information and it is considered as an extra data fostering key encryption technology as in [3,4]. To provide a network access technique for the generation of wireless communications, an emerging multiple access scheme, namely, non-orthogonal multiple access (NOMA) transmission was proposed in many works such as [5]. A Sensors 2019, 19, 736; doi:10.3390/s19030736 www.mdpi.com/journal/sensors
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