The demands for high spectral efficiency and massive connections led the researchers to investigate new multiple access techniques for the future wireless networks. Non- Orthogonal Multiples Access (NOMA) is one of them. Hence, the integration of NOMA technique with the other physical layer techniques like MIMO, cooperative communication and cognitive radio has recently taken considerable attention. Whereas these numerous studies are mostly devoted to reveal the overall capacity and outage performances of NOMA involved systems, the error performances have not been investigated in the literature. In this letter, we analyze error performance of cooperative-NOMA and the exact end-to-end (E2E) bit error probability (BEP) is derived in the closed-form. Then, the derived expressions are validated via simulations. Lastly, the effect of the power allocation coefficient on the error performance is discussed.

In this letter, we propose a deep learning-aided multi-user detection (DeepMuD) in uplink non-orthogonal multiple access (NOMA) to empower the massive machine-type communication where an offline-trained Long Short-Term Memory (LSTM)-based network is used for multi-user detection. In the proposed DeepMuD, a perfect channel state information (CSI) is also not required since it is able to perform a joint channel estimation and multi-user detection with the pilot responses, where the pilot-to-frame ratio is very low. The proposed DeepMuD improves the error performance of the uplink NOMA significantly and outperforms the conventional detectors (even with perfect CSI). Moreover, this gain becomes superb with the increase in the number of Internet of Things (IoT) devices. Furthermore, the proposed DeepMuD has a flexible detection and regardless of the number of IoT devices, the multi-user detection can be performed. Thus, an arbitrary number of IoT devices can be served without a signaling overhead, which enables the grant-free communication.

Non-orthogonal multiple access (NOMA)-based cooperative relaying systems (CRS) are very promising to overcome spectral inefficiency of conventional cooperative communications. Although NOMA-CRS have great recent attention, almost all studies investigate NOMA-CRS only in terms of capacity and outage probability. Error performances of NOMA-CRS have not been regarded. In this paper, we analyze error performance of NOMA-based diamond relaying network (NOMA-DRN) with imperfect successive interference canceler (SIC) as a NOMA-CRS scheme. We derive exact bit error probability (BEP) for NOMA-DRN and provide a tight approximated BEP in the closed-form. In addition, high-SNR analysis is conducted to present that NOMA-DRN has an error floor. Moreover, it is proved that NOMA-DRN turns out to be a non-equiprobable communication and we derive priori probabilities of symbols. All derived expressions are validated via computer simulations.

In this paper, we consider the combination between two promising techniques: space-shift keying (SSK) and nonorthogonal multiple access (NOMA) for future radio access networks. We analyze the performance of SSK-NOMA networks and provide a comprehensive analytical framework of SSKNOMA regarding bit error probability (BEP), ergodic capacity and outage probability. It is worth pointing out all analysis also stand for conventional SIMO-NOMA networks.We derive closedform exact average BEP (ABEP) expressions when the number of users in a resource block is equal to i.e., L = 3. Nevertheless, we analyze the ABEP of users when the number of users is more than i.e., $L \geq 3$ , and derive bit-error-rate (BER) union bound since the error propagation due to iterative successive interference canceler (SIC) makes the exact analysis intractable. Then, we analyze the achievable rate of users and derive exact ergodic capacity of the users so the ergodic sum rate of the system in closedforms. Moreover, we provide the average outage probability of the users exactly in the closed-form. All derived expressions are validated via Monte Carlo simulations and it is proved that SSKNOMA outperforms conventional NOMA networks in terms of all performance metrics (i.e., BER, sum rate, outage). Finally, the effect of the power allocation (PA) on the performance of SSKNOMA networks is investigated and the optimum PA is discussed under BER and outage constraints.

In this letter, we propose threshold-based selective cooperative-NOMA (TBS-C-NOMA) to increase the data reliability of conventional cooperative-NOMA (C-NOMA) networks. In TBS-C-NOMA, the intra-cell user forwards the symbols of cell-edge user after successive interference canceler (SIC) only if the signal-to-interference plus noise ratio (SINR) is greater than the pre-determined threshold value. Hence, the data reliability of the cell-edge user is increased by eliminating the effect of the error propagation. We derive closed-form end-to-end exact bit error probability (BEP) of proposed system for various modulation constellations. Then, the optimum threshold value is analyzed in order to minimize BEP. The obtained expressions are validated via simulations and it is revealed that TBS-C-NOMA outperforms C-NOMA and full diversity order is achieved.

Non-orthogonal multiple access (NOMA) has been a strong candidate to support massive connectivity in future wireless networks. In this regard, its implementation into cooperative relaying, named cooperative-NOMA (CNOMA), has received tremendous attention from researchers. However, most of the existing CNOMA studies have failed to address practical constraints since they assume ideal conditions. Particularly, the error performance of CNOMA schemes with imperfections has not been investigated yet. In this paper, we provide an analytical framework for error and outage performance of CNOMA schemes under practical assumptions where we take into account imperfect successive interference canceler (ipSIC), imperfect channel state information (ipCSI), and hardware impairments (HWI) at the transceivers.We derive analytical expressions of bit error rate (BER) expressions in CNOMA schemes whether the direct links between source and users exist or not which is, to the best of the authors’ knowledge, the first study in the open literature. We also derive the outage probability (OP) expressions for CNOMA schemes with and without direct links under practical assumptions. For comparisons, we provide BER and OP expressions for downlink NOMA with practical constraints which also have not been given in the literature, yet. The theoretical BER and OP expressions are validated with computer simulations where the perfect match is observed. Finally, we discuss the effects of the system parameters (e.g., power allocation, HWI level, ipCSI factor) on the performance of CNOMA schemes to reveal fruitful insights for society. The results demonstrate that the HWI, ipCSI and ipSIC have a significant effect on the performance of the systems.