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A Tutorial on Nonorthogonal Multiple Access for 5G and Beyond
(Wiley-Hindawi, 2018) Aldababsa, Mahmoud; Toka, Mesut; Gokceli, Selahattin; Kurt, Gunes Karabulut; Kucur, Oguz
Today's wireless networks allocate radio resources to users based on the orthogonal multiple access (OMA) principle. However, as the number of users increases, OMA based approaches may not meet the stringent emerging requirements including very high spectral efficiency, very low latency, and massive device connectivity. Nonorthogonal multiple access (NOMA) principle emerges as a solution to improve the spectral efficiency while allowing some degree of multiple access interference at receivers. In this tutorial style paper, we target providing a unified model for NOMA, including uplink and downlink transmissions, along with the extensions to multiple input multiple output and cooperative communication scenarios. Through numerical examples, we compare the performances of OMA and NOMA networks. Implementation aspects and open issues are also detailed.
Non-Orthogonal Multiple Access With Alamouti Space-Time Block Coding
(IEEE-Inst Electrical Electronics Engineers Inc, 2018) Toka, Mesut; Kucur, Oguz
In this letter, we investigate the combination of non-orthogonal multiple access (NOMA) with the conventional Alamouti space-time block coding scheme over Nakagami-m fading environments. In the network, one base station serves multiple users simultaneously by using Alamouti scheme. The exact outage probability (OP) expression is obtained in closed-form. Moreover, asymptotic analysis is also conducted to provide more insights into the OP through diversity order and array gain. The theoretical results verified by the Monte Carlo simulations show that Alamouti scheme can double the diversity order of NOMA network, which also depends on Nakagami channel parameter m and user's ordinal number.
Outage analysis of TAS/MRC in dual hop full-duplex MIMO relay networks with co-channel interferences
(Elsevier Gmbh, 2017) Toka, Mesut; Kucur, Oguz
In this paper, we investigate the outage performance of transmit antenna selection (TAS) and maximal ratio combining (MRC) in dual hop full-duplex (FD) amplify-and-forward (AF) relay network over Rayleigh fading channels. In the analysis, Rayleigh faded multiple co-channel interferers (CCIs) are also taken into account at the relay. In the network, source and destination are equipped with multiple antennas, and relay is equipped with one receive and one transmit antennas, respectively and source destination link is not available. While the TAS is applied at the source without considering residual self-interference (RSI) effect, received signals at the destination are combined based on the MRC technique. For the analysis, we consider three approaches at the relay. In the first, we consider the received signal at the relay is corrupted by faded RSI and noise, in the second one, the RSI is considered as non fading. In the last one, the noise is neglected. In all cases, the relay suffers from multiple Rayleigh faded CCIs. Outage probability (OP) expression related to all the cases is derived and obtained in single integral forms in case of the faded/non-fading RSI and in closed form in case of the noise neglected approach. Moreover, we also find asymptotic OPs and conduct effective diversity order analysis. The analytical results are verified by the Monte Carlo simulations. Results show that TAS decreases error floor at high signal-to-noise ratio (SNR) region and MRC provides diversity gain at low SNR region. In addition, approaches II and III are good approximations to approach I at low and high SNR regions, respectively. (C) 2017 Elsevier GmbH. All rights reserved.
Outage Performance of Dual Hop Full-Duplex MIMO Relay Networks with TAS/MRC over Rayleigh Fading Channels
(IEEE, 2016) Toka, Mesut; Kucur, Oguz
In this paper, we investigate end-to-end (e2e) outage probability (OP) performance of dual hop full-duplex (FD) amplify-and-forward (AF) relay network with transmit antenna selection (TAS) and maximal-ratio combining (MRC) over independent identically distributed Rayleigh fading channels. In the network, source and destination are equipped with multiple antennas, and communicate with each other via a single relay, which is equipped with one receive and one transmit antennas. We assume that the direct link between the source and destination is not available. For signal transmission, TAS is used at the source by neglecting residual self-interference (RSI) effect and maximal-ratio combining (MRC) technique is employed at the destination for combining received signals. In order to simplify the theoretical derivations, we also investigate the e2e OP in case that the RSI is non-fading. OP expression is derived in integral form for the Rayleigh faded RSI effect. Moreover, in case of non-fading RSI effect, OP expression is derived in closed form. The analytical results are verified by the Monte Carlo simulations.
Outage Performance of Dual Hop Full-Duplex Relaying with Alamouti/MRC over Rayleigh Fading Channels
(IEEE, 2017) Toka, Mesut; Kucur, Oguz
In this study, we present a full-duplex (FD) transmission scheme based on conventional Alamouti coding technique and investigate end-to-end (e2e) outage probability (OP) performance over independent identically distributed Rayleigh fading channels in dual-hop relay networks. We assume that direct link is not available due to channel impairments, so that the communication between the source and destination is maintained only via a single relay. In the network, the relay is equipped with one receive and one transmit antennas, and adopts amplify and-forward (AF) and decode-and-forward (DF) protocols. While Alamouti code is used at the transmitter side, maximal-ratio combining (MRC) technique is employed at the destination in order to provide higher diversity order. OP expressions are derived in single integral and closed forms for AF and DF protocols, respectively. In addition, in order to provide insight into OP, asymptotic OP expressions are also derived. The analytical derivations are verified by the Monte Carlo simulations. Results show that e2e performance of the system is improved at low signal-to-noise ratio (SNR) region by increasing the number of antennas at the destination and DF provides approximately 2 dB SNR gain as compared to AF.
Outage Performance of Dual-Hop TAS/Alamouti-STBC NOMA System
(IEEE, 2020) Toka, Mesut; Kucur, Oguz
In this study, outage performance of dual-hop non-orthogonal multiple access system, where the base station simultaneously communicates with two mobile users via a half-duplex amplify-and-forward relay by applying transmit antenna selection/Alamouti space-time block coding technique, is investigated over Raylegih fading channels. By defining fundamental analytical equations, the outage probability of both mobile users is investigated via Monte Carlo simulations. Simulation results demonstrate that outage probability performance of the user with lower power allocation can be improved by the proposed technique, but it does not change for the other user.
Outage Performance of OSTBC-NOMA System in the presence of Channel Estimation Error and Feedback Delay
(IEEE, 2019) Toka, Mesut; Kucur, Oguz; Demirkol, Busra
In this study, outage performance of non-orthogonal multiple access (NOMA) system with orthogonal space-time block coding (OSTBC) is investigated over Nakagami-m fading channels in the presence of channel estimation errors and feedback delay. In the system, one base station with multiple antennas serves simultaneously multiple mobile users with single antenna by using OSTBC technique. The outage probability related to any mobile user, which is expressed with the help of end-to-end signal-to-interference plus noise ratio, is investigated through Monte Carlo simulations.
Outage Performance of Partial Antenna Selection in the Full-Duplex Decode-and-Forward Relay Networks
(IEEE, 2017) Toka, Mesut; Kucur, Oguz
In this study, outage probability of partial antenna selection in the full-duplex decode-and-forward multiple-input multiple-output relay networks is investigated over Rayleigh fading channels. In the considered relay network the source, relay and destination are equipped with multiple antennas and it is assumed that direct link is not available due to heavy channel conditions. For signal transmission from the source to destination, while partial antenna selection technique is used in which antennas maximizing the instantaneous signal-to-interference plus noise ratio for the first hop are selected, a single antenna is selected at the destination. End-to-end outage probability expression of the relay network is obtained in closed form and approximated asymptotic expression is also derived. Analytical results are validated by Monte Carlo simulations.
Outage Probability of Full-Duplex MIMO Relay Networks with Co-channel Interference over Rayleigh Fading Channels
(IEEE, 2016) Toka, Mesut; Kucur, Oguz
In this work, the outage probability of dual-hop full-duplex amplify-and-forward MIMO relay network is examined in the presence of co-channel interference at the relay over Rayleigh fading channels. The source and destination are equipped with multiple antennas and the relay is equipped with single receive and single transmit antennas. The effects of Rayleigh faded multiple co-channel interferences and self-interference between transmit/receive antennas of the relay are considered. In this relay network, transmit antenna selection at the source and maximal-ratio combining technique at the destination are employed. The outage probability of the relay network is examined via Monte Carlo simulations.
Outage Probability of Max-Max Antenna Selection in Dual-Hop Full Duplex Amplify-and-Forward Relaying Network over Nakagami-m Fading Channel
(IEEE, 2019) Demirkol, Busra; Toka, Mesut; Kucur, Oguz
In this paper, outage probability of max-max antenna selection method in the full-duplex amplify-and-forward relaying networks is examined over Nakagami-m fading channels. In the network, the source, relay and destination are equipped with multiple antennas. We assume that direct transmission link between the source and destination does not exist because of poor channel conditions. Transmit and receive antenna pair with the best signal-to-noise ratio is selected for signal transmission in both hops. Outage probability expression of the system is obtained in single integral form and verified by Monte Carlo simulations.
Performance analyses of TAS/Alamouti-MRC NOMA in dual-hop full-duplex AF relaying networks
(Wiley, 2023) Toka, Mesut; Guven, Eray; Durmaz, Mehmet Akif; Kurt, Gunes Karabulut; Kucur, Oguz
In this article, performance of a multi-user downlink non-orthogonal multiple access system in dual-hop full-duplex amplify-and-forward relaying networks is investigated over Nakagami-m fading channels in the presence of channel estimation error and feedback delay. The base station applies transmit antenna selection (TAS)/Alamouti space-time block coding scheme, while the users exploit maximum-ratio combining to utilize benefits of receive diversity. To demonstrate superiority of the proposed system, outage probability (OP) is inves-tigated, and tight lower bound expression is derived to support the exact OP. Moreover, asymptotic analyzes are also conducted for ideal and practical condi-tions to provide further insights into the OP in high signal-to-noise ratio region. In addition, software defined radio based test-bed implementation is realized to confirm the analysis and show feasibility of the proposed system. Theoreti-cal analyzes verified by simulations and practical implementations demonstrate that more performance improvement can be achieved for the weakest user (with the lowest channel gain) in the case of practical conditions when compared to ideal cases. Also, both diversity order and array gain are dominant in achieving minimum OP (based on relay location) in ideal conditions, while only array gain has effect in practical manner.
Performance analyses of TAS/Alamouti-MRC NOMA system with channel estimation error, feedback delay, and imperfect SIC
(Wiley, 2021) Toka, Mesut; Kucur, Oguz
In this article, the performance of a power domain downlink multiple-input multiple-output non-orthogonal multiple access system, where the base station (BS) equipped with three antennas communicates simultaneously with three mobile users equipped with multiple antennas, is analyzed over Nakagami-m fading channels in the presence of channel estimation error (CEE), feedback delay (FBD), and imperfect successive interference cancellation. In the considered system, the BS applies transmit antenna selection (TAS)/Alamouti-space-time block coding (STBC) scheme while mobile users are assumed to adopt maximum-ratio combining technique in order to take advantage of the combination of transmit and receive diversities. In particular, in order to apply Alamouti-STBC scheme at the BS, one of the transmit antennas is determined randomly while the other one is selected according to decision of the majority of mobile users. For performance metrics, closed-form outage probability (OP) and ergodic capacity (EC) expressions derived with the help of moment generating function approach. Moreover, asymptotic analyses are maintained to demonstrate the effects of CEE and FBD in terms of diversity order and array gain. We show that the proposed system provides better OP and EC performance than the system without antenna selection for different users and conditions.
Performance Analysis of OSTBC-NOMA System in the Presence of Practical Impairments
(IEEE-Inst Electrical Electronics Engineers Inc, 2020) Toka, Mesut; Kucur, Oguz
This paper investigates the performance of a powerdomain downlink non-orthogonal multiple access (NOMA) system in the presence of practical impairments such as channel estimation error (CEE), feedback delay (FBD) and imperfect successive interference cancellation (SIC), where the base station communicates with multiple users by applying orthogonal space-time block coding (OSTBC) technique in order to exploit the benefits of transmit diversity. Outage probability (OP), ergodic capacity and fairness index analyses are conducted in case channels are subjected to Nakagami-m fading in order to illustrate the level of system performance, and closed-form mathematical expressions are obtained. Furthermore, to demonstrate the impact of CEE and FBD, asymptotic OP is also maintained. The analytical results validated by MonteCarlo simulations demonstrate that all performancemetrics reach a non-zero fixed value in high signal-to-noise region due to the CEE and FBD while imperfect SIC worsens the performance of user with the lowest power allocation to the full outage. In addition, NOMA outperforms its counterpart orthogonal multiple access in terms of OP and ergodic capacity generally. Also, G2-OSTBC code has higher fairness index than G3-OSTBC code.
Performance of antenna selection schemes in dual hop full-duplex decode-and-forward relaying over Nakagami-m fading channels
(Elsevier Gmbh, 2018) Toka, Mesut; Kucur, Oguz
In this paper, we investigate the outage performance of several antenna selection (AS) schemes in dual hop full duplex (FD) multiple-input multiple-output (MIMO) relay networks in which the relay adopts decode-and-forward (DF) protocol over Nakagami-m fading channels. In the network, the source (S), destination (D) and relay (R) are assumed to be equipped with multiple antennas. We assume that the line-of-sight component between S and D cannot be established due to the poor fading environment conditions. For signal transmission-reception during the training period, only a single antenna at each node is selected according to selection techniques, and then with the help of an error-free feedback channel the selected antenna index is sent to the related node. Outage probability (OP) expressions related to AS schemes are obtained in closed forms and asymptotic OPs are also derived in order to get more meaningful insights into OP and diversity behaviour. The theoretical results are verified by Monte Carlo simulations. We show that performance of the FD relay can be significantly improved by using selection techniques compared to half-duplex (HD), especially at low signal-to-noise ratio (SNR) region. In addition, results show that the performance floor level meaning zero diversity at high SNR region, which is also confirmed by asymptotic analysis and is an inherent disadvantage of FD relay, can be decreased. Moreover, it is shown that the FD relay with AS schemes outperforms HD as the target rate increases for a certain value of SNR and residual self-Interference power.
Performance of dual-hop full-duplex relay networks with orthogonal space-time block coding in Nakagami-m fading channels
(Inst Engineering Technology-Iet, 2019) Toka, Mesut; Kucur, Oguz
In this study, the authors investigate outage performance of orthogonal space-time block coding (OSTBC) in dual-hop multiple-input multiple-output full-duplex (FD) amplify-and-forward relay networks over flat Nakagami-m fading environments. In the network, OSTBC and maximum-ratio combining (MRC) are employed at the source and destination, respectively, while the relay has one receive and one transmit antennas. In order to analyse the system, outage probability (OP) expression is obtained in single integral form. In addition, lower-bound and asymptotic expressions are also derived in closed forms in order to provide more insights into OP. The theoretical derivations are verified by Monte Carlo simulations. The results reveal that the quality of self-interference (SI) cancellation, the number of antennas at the destination and channel condition in the first hop are quite effective in performance improvement. FD outperforms half-duplex one when the SI cancellation parameter is kept below a certain value for fixed signal-to-noise ratio values, and when the target rate is greater than a certain value, if the quality of SI cancellation is quite enough. Moreover, performance analysis of the system is extended to other transmit diversity techniques such as maximum-ratio transmission / MRC and transmit antenna selection/MRC, and comparisons are presented.
Performance of Joint Relay and Antenna Selection in the Full-Duplex Amplify-and-Forward Relay Networks
(IEEE, 2015) Toka, Mesut; Kucur, Oguz; Tezekici, Bekir Sami
In this work, joint relay and antenna selection (JRAS) problem in Full-Duplex (FD) Amplify-and-Forward (AF) relaying network is examined. A dual-hop relay system with one source, one destination and N FD AF relays is considered. Each FD relay is equipped with N,. antennas for receiving and N, antennas for transmitting. In this FD relay system, joint selection strategy involves choosing the best single relay and the best single receive/transmit antenna at the source-to-relay/relay-to-destination links. The system model is developped and the outage probability (OP) and the bit error rate (BER) of the system for different numbers of relay and antenna cases are examined in Rayleigh fading channel via Monte Carlo simulations.
Performance of Joint Relay and Antenna Selection in the Full-Duplex Amplify-and-Forward Relay Networks
(Springer, 2017) Toka, Mesut; Kucur, Oguz; Tezekici, Bekir S.
This paper focuses on the joint relay and antenna selection problem in dual hop full-duplex (FD) relay network with one source, one destination and N FD amplify-and-forward relays in flat Rayleigh fading channels. In the network, the source and destination are both equipped with single antenna, and all of the relays are equipped with antennas for reception and antennas for transmission. For this FD relay system, we investigate different relay selection schemes such as best relay selection, partial relay selection and reactive relay selection together with the best single receive/transmit antenna of the selected relay for the source-to-relay/relay-to-destination links based on the instantaneous channel conditions. To facilitate comparisons between the relay selection schemes, we derive closed-form outage probability (OP), and calculate bit error rate numerically. Moreover, asymptotic approximations of the OP are also derived. Analytical results are validated by the Monte Carlo simulations.
Performance of MRT/RAS MIMO-NOMA With Residual Hardware Impairments
(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Toka, Mesut; Kucur, Oguz
In this letter, outage probability (OP) of maximum-ratio transmission/receive antenna selection structure is analyzed in a single hop downlink multi-user multiple-input multiple-output non-orthogonal multiple access system. Theoretical analysis is conducted for Nakagami-m fading channels by considering residual hardware impairments (RHIs), channel estimation errors (CEEs) and imperfect successive interference cancellation (ipSIC) effects. Also, asymptotic OP expression is obtained to demonstrate the impact of practical impairments. According to theoretical results verified by Monte Carlo simulations, RHIs and ipSIC have only impact on array gain while CEEs cause zero diversity on the system performance.

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