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Wireless Communications and Mobile Computing

Exploiting Opportunistic Scheduling for Physical‐Layer Security in Multitwo User NOMA Networks

Kyusung Shim, Beongku An

Published Jan 1, 2018• 9 citations
Publisher

Abstract

In this paper, we address the opportunistic scheduling in multitwo user NOMA system consisting of one base station, multinear user, multifar user, and one eavesdropper. To improve the secrecy performance, we propose the users selection scheme, called best‐secure‐near‐user best‐secure‐far‐user (BSNBSF) scheme. The BSNBSF scheme aims to select the best near‐far user pair, whose data transmission is the most robust against the overhearing of an eavesdropper. In order to facilitate the performance analysis of the BSNBSF scheme in terms of secrecy outage performance, we derive the exact closed‐form expression for secrecy outage probability (SOP) of the selected near user and the tight approximated closed‐form expression for SOP of the selected far user, respectively. Additionally, we propose the descent‐based search method to find the optimal values of the power allocation coefficients that can minimize the total secrecy outage probability (TSOP). The developed analyses are corroborated through Monte Carlo simulation. Comparisons with the random‐near‐user random‐far‐user (RNRF) scheme are performed and show that the proposed scheme significantly improves the secrecy performance.

DOI
10.1155/2018/2797824

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In this paper, we address the opportunistic scheduling in multitwo user NOMA system consisting of one base station, multinear user, multifar user, and one eavesdropper. To improve the secrecy performance, we propose the users selection scheme, called best‐secure‐near‐user best‐secure‐far‐user (BSNBSF) scheme. The BSNBSF scheme aims to select the best near‐far user pair, whose data transmission is the most robust against the overhearing of an eavesdropper. In order to facilitate the performance analysis of the BSNBSF scheme in terms of secrecy outage performance, we derive the exact closed‐form expression for secrecy outage probability (SOP) of the selected near user and the tight approximated closed‐form expression for SOP of the selected far user, respectively. Additionally, we propose the descent‐based search method to find the optimal values of the power allocation coefficients that can minimize the total secrecy outage probability (TSOP). The developed analyses are corroborated through Monte Carlo simulation. Comparisons with the random‐near‐user random‐far‐user (RNRF) scheme are performed and show that the proposed scheme significantly improves the secrecy performance.
In this paper, we study how to improve physical layer security capability of multiple near users and multiple far users non-orthogonal multiple access (NOMA) networks. To this end, we propose an opportunistic user scheduling scheme, named the best-secure-near-user best-secure-far-user (BSNBSF) scheme. The BSNBSF aims to select the best near-far user pair, whose data transmission is the most robust against the interception of an eavesdropper. In order to facilitate the performance analysis of the proposed user scheduling scheme in terms of secrecy outage probability (SOP), we derive an exact closed-form expression and a tight approximate closed-form expression for the SOP of the selected near and far users, respectively. Numerical results show that the BSNBSF scheme significantly improves the secrecy outage performance NOMA networks compared to that of the random near user and random far user selection scheme. Additionally, discussions on the complicate convex characteristic of the total SOP with respect to the power allocation coefficients and the impact the number of near and/or far users are provided.
This paper studies opportunistic scheduling schemes to enhance the secrecy performance in multi-user multiple-input single-output (MU-MISO) non-orthogonal multiple access (NOMA) systems, in which a multiple antenna base station (BS) serves multiple single-antenna cell-center and cell-edge users in the presence of multiple single-antenna eavesdroppers. In order to improve the secrecy performance, we propose an opportunistic scheduling scheme, called the proposed antenna/users selection (PAUS) scheme. Additionally, we consider two practical eavesdropping scenarios, namely colluding and non-colluding eavesdroppers. We derive the exact closed-form expression for secrecy outage probability (SOP) and asymptotic SOP of the PAUS scheme under different eavesdropping scenarios. We provide the 2D golden section search-based algorithm to find the optimal values of the transmit power and power allocation coefficient that minimize the system secrecy outage performance. The developed analyses are verified by Monte Carlo simulations. The numerical results show that the PAUS scheme improves secrecy performances compared to the benchmark random antenna/users selection (RAUS) scheme. To provide further insights into the system secure performance, the effects of transmit signal-to-noise ratio (SNR), power allocation coefficient, the number of transmit antennas at the BS, number of cell-center and cell-edge users, and the eavesdropper placements are extensively evaluated and discussed.
In this paper, we propose a novel transmit antenna selection (TAS) scheme to improve the physical layer security of two-user non-orthogonal multiple access (NOMA) systems. Specifically, the proposed TAS scheme aims to select an antenna that is the most robust against the interception of an eavesdropper, in particular, the antenna that minimizes the maximum capacity of the eavesdropper channels. To evaluate the performance of the proposed scheme, we derive an exact closed-form expression for the secrecy outage probability (SOP) of the near user and a tight approximated closed-form expression for the SOP of the far user. Numerical results reveals that the proposed TAS scheme improves the total secrecy outage probability compared to that of some existing schemes. We also provide some insightful discussions on the impact of the number of antenna and the location of the eavesdropper on the security capability of the considered system.
In this paper, we investigate secure transmission in a cooperative non-orthogonal multiple access (NOMA) system in the presence of an active eavesdropper. To enhance secrecy performance, we propose two approaches. The first is a novel cooperative NOMA architecture, in which the cell-edge user generates a jamming signal to degrade the eavesdropper’s channel condition. The second is a novel opportunistic scheduling scheme, referred to as the minimum antenna selection (MAS) scheme, which selects the transmit antenna at the source node to minimize the maximum eavesdropper channel capacity between the cell-center and cell-edge users. We derive closed-form expressions for the secrecy outage probability (SOP) of both the cell-center and cell-edge users to characterize the impact of various network parameters on secrecy performance. Through numerical results, we analyze the impact of the source, cell-center, and cell-edge users’ transmit power on the SOP; the impact of the power allocation coefficient, target secrecy rate, and eavesdropper transmit power on the total SOP; and the impact of the distance between the source node and the eavesdropper, as well as the distance between the cell-center user and the eavesdropper, on the secrecy sum throughput (SST). These results demonstrate that the proposed cooperative NOMA architecture and the MAS scheme can effectively protect confidential messages against active eavesdropping attacks.
We investigate physical layer security of an uplink NOMA system consisting of one base station, multiple users and one eavesdropper. During each uplink transmission, two users are paired to perform NOMA and another user is opportunistically selected from the remaining idle users to act as a friendly jammer to emit artificial noise for confusing the eavesdropper. To enhance the transmission security for the system, we propose two friendly jammer selection aided uplink NOMA transmission schemes, namely random jammer selection aided uplink NOMA transmission (RJS-UNT) scheme without knowing the eavesdropper's channel state information (CSI), and optimal jammer selection aided uplink NOMA transmission (OJS-UNT) scheme where the eavesdropper's CSI is available. For comparison purpose, a non-jammer selection aided uplink NOMA transmission (NJS-UNT) scheme is also considered. Analytical closed-form expressions for the secrecy outage probability (SOP) are derived to evaluate the secrecy performance achieved by the proposed schemes. Also, the asymptotic SOPs are provided to obtain further insights. The analysis and simulation results indicate that the schemes converge to SOP floors with the increasing SNR, while the floors achieved by the RJS-UNT and OJS-UNT schemes are significantly lower than that achieved by the NJS-UNT scheme, showing the security advantage of the proposed schemes.
The secrecy outage probability (SOP) performance is investigated for a cooperative non-orthogonal multiple access system under eavesdropping attack, where a base station transmits signals to a far user via a full-duplex relay, and to a near user directly at the same time, in the presence of an eavesdropper. All nodes are configured with multiple antennas and antenna selection is adopted by the base station and relay to enhance the security performance. The exact and asymptotic closed-form SOP expressions are derived, which incorporate the impact of imperfect channel state information and apply to general cases considering the quality of service of the far and near users, whether or not the wiretap channel is known, and the location of the eavesdropper. Monte Carlo simulations corroborate the analysis and the superiority of the proposed system over the single-antenna system and the one without antenna selection. It is also revealed that the asymptotic SOP performance of the near user is nearly independent of the power allocation.