42 research outputs found

    Secrecy Outage Probability of Energy-Harvesting Cooperative NOMA Transmissions with Relay Selection

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    Three relay selection techniques, aiming at achieving secure non-orthogonal multiple access in cooperative energy-harvesting (EH) communications, are proposed and compared. In the cooperative relaying system, the source node communicates with multiple users through amplify-and- forward EH relays in the presence of a passive eavesdropper. The relay selection is a two-stage strategy, where the first stage aims at achieving the users’ target data rate, and the second aims at optimizing the secrecy outage probability. New explicit analytical expressions for the secrecy outage probability are derived for three operating scenarios: i) when the channel state information (CSI) of the eavesdropper is unknown, and a two-stage conventional relay selection scheme is considered, ii) when CSI of the eavesdropper is known, and a two- stage optimal relay selection scheme is used, and iii) when multiple relays participate in forwarding the signal to the end users. Monte-Carlo simulations are provided to confirm the derivations, and the effects of the main system parameters on its secrecy are investigated. In particular, it is shown that the optimal relay selection scheme outperforms the conventional and the multiple-relays schemes in terms of secrecy outage probability, and that this superiority becomes more obvious when the number of the relays increases

    NOMA in Cooperative Communication Systems with Energy-Harvesting Nodes and Wireless Secure Transmission

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    In this paper, non-orthogonal multiple access (NOMA) in cooperative relay system is considered, where a source node communicates with a pair of energy harvesting (EH) user equipments through a multiple antennas relay node. A hybrid protocol is adopted at the relay, in which if the relay can successfully decode the signals, decode- and-forward (DF) protocol will be adopted to forward the signals to the users. Otherwise, amplify-and-forward (AF) protocol will be implemented. Assuming that the users adopt maximal ratio combining (MRC) to combine the received signals in the two cooperative phases, new explicit analytical expressions for the average sum-rate are derived when the relay works in, 1) AF mode, and 2) DF mode, in two scenarios when one user is the stronger in both cooperation phases, and when an alternative user is stronger in each phase. Then, the investigation is extended to the case where the relay is an untrusted node, and cooperative jamming technique is proposed to degrade the ability of the relay to decode the signals and enforce the relay to operate always in AF mode. For the untrusted relay scenario, new analytical expression for the average secrecy rate is derived. Monte Carlo simulations are provided to validate the analysis. The simulation results reveal that the location of the relay is the key parameter to achieve the best performance

    SWIPT-Enabled Cooperative NOMA With mth Best Relay Selection

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    Non-orthogonal multiple access (NOMA) was recently regarded as a potential technique for next generation wireless networks. Recent works on relay selection for cooperative NOMA systems have mainly addressed the best relay selection to forward its received signals to terminal nodes. Nonetheless, in practical scenarios, the best relay may be unavailable due to non-ideal conditions such as scheduling and overload constraints or possibly due to channel feedback delay. Therefore, there is compelling need to consider a more practical solution, in which the best available relay is selected. In this article, we examine the error rate performance for simultaneous wireless information and power transfer (SWIPT)-enabled NOMA, while considering the selection of the mth best available relay. In particular, we present an exact pairwise error probability (PEP) expression to obtain a bit error rate (BER) upper bound. The asymptotic PEP is investigated to evaluate the achievable diversity order for NOMA users. Finally, simulation results are provided to verify the accuracy of the derived PEP expressions and to give more insights into the system performance.publishedVersionPeer reviewe

    On secure system performance over SISO, MISO and MIMO-NOMA wireless networks equipped a multiple antenna based on TAS protocol

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    This study examined how to improve system performance by equipping multiple antennae at a base station (BS) and all terminal users/mobile devices instead of a single antenna as in previous studies. Experimental investigations based on three NOMA down-link models involved (1) a single-input-single-output (SISO) scenario in which a single antenna was equipped at a BS and for all users, (2) a multi-input-single-output (MISO) scenario in which multiple transmitter antennae were equipped at a BS and a single receiver antenna for all users and (3) a multi-input-multi-output (MIMO) scenario in which multiple transmitter antennae were equipped at a BS and multiple receiver antenna for all users. This study investigated and compared the outage probability (OP) and system throughput assuming all users were over Rayleigh fading channels. The individual scenarios also each had an eavesdropper. Secure system performance of the individual scenarios was therefore also investigated. In order to detect data from superimposed signals, successive interference cancellation (SIC) was deployed for users, taking into account perfect, imperfect and fully imperfect SICs. The results of analysis of users in these three scenarios were obtained in an approximate closed form by using the Gaussian-Chebyshev quadrature method. However, the clearly and accurately presented results obtained using Monte Carlo simulations prove and verify that the MIMO-NOMA scenario equipped with multiple antennae significantly improved system performance.Web of Science20201art. no. 1

    Analysis and Design of Non-Orthogonal Multiple Access (NOMA) Techniques for Next Generation Wireless Communication Systems

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    The current surge in wireless connectivity, anticipated to amplify significantly in future wireless technologies, brings a new wave of users. Given the impracticality of an endlessly expanding bandwidth, there’s a pressing need for communication techniques that efficiently serve this burgeoning user base with limited resources. Multiple Access (MA) techniques, notably Orthogonal Multiple Access (OMA), have long addressed bandwidth constraints. However, with escalating user numbers, OMA’s orthogonality becomes limiting for emerging wireless technologies. Non-Orthogonal Multiple Access (NOMA), employing superposition coding, serves more users within the same bandwidth as OMA by allocating different power levels to users whose signals can then be detected using the gap between them, thus offering superior spectral efficiency and massive connectivity. This thesis examines the integration of NOMA techniques with cooperative relaying, EXtrinsic Information Transfer (EXIT) chart analysis, and deep learning for enhancing 6G and beyond communication systems. The adopted methodology aims to optimize the systems’ performance, spanning from bit-error rate (BER) versus signal to noise ratio (SNR) to overall system efficiency and data rates. The primary focus of this thesis is the investigation of the integration of NOMA with cooperative relaying, EXIT chart analysis, and deep learning techniques. In the cooperative relaying context, NOMA notably improved diversity gains, thereby proving the superiority of combining NOMA with cooperative relaying over just NOMA. With EXIT chart analysis, NOMA achieved low BER at mid-range SNR as well as achieved optimal user fairness in the power allocation stage. Additionally, employing a trained neural network enhanced signal detection for NOMA in the deep learning scenario, thereby producing a simpler signal detection for NOMA which addresses NOMAs’ complex receiver problem

    Performance Analysis for NOMA Relaying System in Next-Generation Networks with RF Energy Harvesting

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    In this chapter, we investigate the performance of the non-orthogonal multiple access (NOMA) relaying network with radio-frequency (RF) power transfer. Specifically, this considered system consists of one RF power supply station, one source, one energy-constrained relay, and multiple energy-constrained NOMA users. The better user and relay can help the source to forward the message to worse user by using the energy harvested from the power station. The triple-phase harvest-transmit-forward transmission protocol is proposed for this considered system. The exact closed-form expressions of outage probability and throughput for each link and whole system are derived by using the statistical characteristics of signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) of transmission links. In order to understand more detail about the behavior of this considered system, the numerical results are provided according to the system key parameters, such as the transmit power, number of users, time switching ratio, and power allocation coefficients. The simulation results are also provided to confirm the correctness of our analysis

    Investigation on Evolving Single-Carrier NOMA into Multi-Carrier NOMA in 5G

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    © 2013 IEEE. Non-orthogonal multiple access (NOMA) is one promising technology, which provides high system capacity, low latency, and massive connectivity, to address several challenges in the fifth-generation wireless systems. In this paper, we first reveal that the NOMA techniques have evolved from single-carrier NOMA (SC-NOMA) into multi-carrier NOMA (MC-NOMA). Then, we comprehensively investigated on the basic principles, enabling schemes and evaluations of the two most promising MC-NOMA techniques, namely sparse code multiple access (SCMA) and pattern division multiple access (PDMA). Meanwhile, we consider that the research challenges of SCMA and PDMA might be addressed with the stimulation of the advanced and matured progress in SC-NOMA. Finally, yet importantly, we investigate the emerging applications, and point out the future research trends of the MC-NOMA techniques, which could be straightforwardly inspired by the various deployments of SC-NOMA
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