Downlink NOMA Systems Research Articles

Movable Antenna Empowered Downlink NOMA Systems: Power Allocation and Antenna Position Optimization

Movable Antenna Empowered Downlink NOMA Systems: Power Allocation and Antenna Position Optimization

Maximizing energy efficiency for covert communication in NOMA systems with reradiating on antenna

A resource allocation method is proposed to maximize the energy efficiency for covert communication in downlink NOMA systems via reradiating on antennas. Firstly, the optimization problem of maximizing the effective covert energy efficiency of the covert user is constructed under the condition of satisfying the outage probability of the public user and the error detection probability of the warden. Then, the optimization problem is simplified, and the solution of the optimization problem is given when the power allocation coefficient of NOMA is known. Finally, the optimal solution is obtained by traversing the power allocation coefficient of NOMA and solving the optimization problem for each power allocation coefficient. The simulation results show that with the increase of the total power, the energy efficiency first increases and then tends to a constant, that is, there is an optimal value of the power allocation coefficient, which maximizes the energy efficiency.

Iterative signal detection based soft interference cancellation for satellite-terrestrial downlink NOMA systems

Iterative signal detection based soft interference cancellation for satellite-terrestrial downlink NOMA systems

Outage Performance Analysis and Optimization of Two-User Downlink NOMA Systems with Imperfect SIC and Improper Signaling

Outage Performance Analysis and Optimization of Two-User Downlink NOMA Systems with Imperfect SIC and Improper Signaling

Ultrafast Resource Allocation by Parallel Bandit Architecture Using Chaotic Lasers for Downlink NOMA Systems

Ultrafast Resource Allocation by Parallel Bandit Architecture Using Chaotic Lasers for Downlink NOMA Systems

BER performance analysis for downlink NOMA systems over cascaded Nakagami-m fading channels

BER performance analysis for downlink NOMA systems over cascaded Nakagami-m fading channels

Preserving Covert Communication in Downlink NOMA Systems via Reradiating on Antennas

Preserving Covert Communication in Downlink NOMA Systems via Reradiating on Antennas

Joint Design of Polar Coding and Physical Network Coding for Two-User Downlink Non-Orthogonal Multiple Access.

In this paper, we propose a joint polar coding and physical network coding (PNC) for two-user downlink non-orthogonal multiple access (PN-DNOMA) channels, since the successive-interference-cancellation-aided polar decoding cannot be optimal for finite blocklength transmissions. In the proposed scheme, we first constructed the XORed message of two user messages. Then, the XORed message was superimposed with the message of the weak User 2 for broadcast. By doing so, we can utilize the PNC mapping rule and polar decoding to directly recover the message of User 1, while at User 2, we equivalently constructed a long-length polar decoder to obtain its user message. The channel polarization and decoding performance can be greatly improved for both users. Moreover, we optimized the power allocation of the two users with their channel conditions by considering the user fairness and the performance. The simulation results showed that the proposed PN-DNOMA can achieve performance gains of about 0.4-0.7 dB over the conventional schemes in two-user downlink NOMA systems.

Adaptive clustering with continuous phase modulation in NOMA systems

ABSTRACT Power-domain NOMA can enlarge the spectrum efficiency and capacity via serving multiple users in the same time slot. Up to now, there are still some issues to be addressed in the NOMA system with multiple users: how many users the NOMA system can accommodate with limited power, how to mitigate the interference among the users, what’s the achievable bound of capacity with limited power at the base station, and how to tackle with two or more users having similar distances to the base station. In the paper, the approximated CPM capacity in the NOMA system over Rayleigh channel is derived. Then, an adaptive user-clustering is proposed in downlink NOMA system, such that the achievable sum-rate will get high enough. Moreover, the optimal allocation of power for each user in each cluster is derived and evaluated. In the end, the performances such as outage probability, capacity, peak-to-average power ratio (PAPR), and bit error ratio (BER) are simulated as comparison.

Achieving Near Ideal Covertness in NOMA Systems With Channel Inversion Power Control

In this letter, we propose two resource allocation schemes for covert communication in a downlink NOMA system, where the transmitter can send information simultaneously both to the public and the covert receiver, while maintaining ideal (or near-ideal) covertness with respect to the warden. The covert transmission is concealed by combining NOMA and channel inversion power control, acting as a random source of uncertainty at the warden. The transmission scheme supports zero outage transmission to the public user and non-zero outage transmission to the covert user, while guaranteeing an ideal or near-ideal covertness at the warden, depending on whether the covert user employs single-user decoding or successive interference cancellation (SIC) decoding. In the latter case, we determine the optimal power sharing factor between the public and covert signals that maximizes the average covert throughput, given a predefined fixed transmission rate to the public user. If the channel between the transmitter and the covert receiver is moderate or strong, the SIC decoding, compared to the single-user decoding, leads to much higher covert throughput at the cost of minor degradation of covertness.

Compressed Sensing Based Power Allocation and User Selection with Adaptive Resource Block Selection for Downlink NOMA Systems

Compressed Sensing Based Power Allocation and User Selection with Adaptive Resource Block Selection for Downlink NOMA Systems

Enhanced performance analysis with exact solutions for downlink-NOMA system in vehicular communications

This research presents an enhanced performance analysis process for the power domains of downlink-NOMA systems for vehicular communication over Rayleigh fading channels. We derived exact closed-form expressions of outage probability (OP), bit error rate (BER), outage capacity (OC), and average channel capacity (AVC) by using binary phase-shift keying (BPSK) modulation. All channel parameters required for downlink-NOMA system performance analysis were combined. The theoretical and simulation results perfectly confirmed one another. The obtained results were then compared with results from the literature, based on similar parameters. It was found that the proposed system increased the performance by 34 times for OP at SNR=15 dB, 92% and 22% for BER at SNR=24 dB, and 59% for AVC at SNR=30 dB. Finally, this study introduces exact solutions that will greatly accelerate NOMA system analysis by exploiting information in the existing database for analytical design processes based on communication theory.

Density-based user clustering in downlink NOMA systems

Density-based user clustering in downlink NOMA systems

Fast generalized threshold‐based signal detection for multiuser downlink NOMA systems with arbitrary power allocation

SummaryNon‐orthogonal multiple access (NOMA) is a technique to improve spectral efficiency. Based on the constellation relationship (CR) between the superposition‐coded signal and individual user's signals, in the literature, a simple detection scheme threshold‐based signal detection has been proposed for the two‐user downlink NOMA (DL‐NOMA) system with specific power allocations, not arbitrary power allocation. Furthermore, the average symbol error probability (ASEP) with squared M‐ary quadrature amplitude modulation for two‐user DL‐NOMA systems has also been derived based on this CR. Based on the threshold‐based signal detection for the two‐user DL‐NOMA systems with specific power allocation, in this paper, a generalized threshold‐based signal detection is proposed for all users in the multiuser DL‐NOMA systems with arbitrary power allocation, and then a fast generalized threshold‐based signal detection is further proposed. The generalized ASEP for each individual user in the multiuser DL‐NOMA system is further derived in Rayleigh fading channels. Both theoretical ASEP and simulated symbol error rate results validate the fast generalized threshold‐based signal detection scheme and the generalized ASEP for multiuser DL‐NOMA systems with arbitrary power allocations.

Performance analysis of downlink-NOMA over generalized-k fading channels

Due to the increasing demand for higher capacity in mobile communication devices, non-orthogonal multiple access (NOMA) has become a promising technique. Compared to existing orthogonal multiple access methods, NOMA can serve multiple users with better spectral efficiency by allowing co-channel interference, thus its reliability performance over various channel models needs further research. In this paper, closed-form outage probability, average channel capacity and symbol error rate are derived for a downlink-NOMA system with an arbitrary number of users over generalized-K fading channels. Finally, theoretical findings are validated via Monte Carlo simulations for several channel parameters.

Low Density Code design for downlink NOMA system

Low Density Code design for downlink NOMA system

Performance evaluation of a power allocation algorithm based on dynamic blocklength estimation for URLLC in the multicarrier downlink NOMA systems

Performance evaluation of a power allocation algorithm based on dynamic blocklength estimation for URLLC in the multicarrier downlink NOMA systems

Lowest-Opportunities User First-Based Subcarrier Allocation Algorithm for Downlink NOMA Systems

Lowest-Opportunities User First-Based Subcarrier Allocation Algorithm for Downlink NOMA Systems

Secrecy Performance Analysis of the NOMA System on High-Speed Railway

High-speed railway (HSR) wireless communications are required to ensure strict security. In this work, we study the secrecy performance of a nonorthogonal multiple access- (NOMA-) aided HSR wireless communication system in the case of an eavesdropping user. Specifically, applying NOMA technology to the HSR communication system can effectively improve the data rates. Therefore, we study the secrecy performance of the downlink NOMA system under the HSR wireless communication. In particular, the exact analytical results for the secrecy outage probability (SOP) based on no small-scale channel state information (CSI) are derived. We also provide all of the parameterizations for the proposed channel model. Finally, the correctness of theoretical derivation is verified via simulations. Results show the positive effect of utilizing the NOMA for enhancing wireless systems secrecy performance.

Efficient user pairing algorithm for enhancement of spectral efficiency and interference cancelation in downlink NOMA system

A new subcarrier-user allocation algorithm for the downlink non-orthogonal multiple access system is presented in this paper. The proposed algorithm aims to enhance the spectral efficiency of the system and the successive interference cancelation performance by guaranteeing a high difference in channel-gain between the paired users per subcarrier. To enhance the spectral efficiency, the proposed algorithm provides a higher priority to the subcarrier that has a higher best (maximum) channel gain value rather than that has a lower best channel gain value. Also, it pairs the strong user with the second minimum channel-gain user rather than the minimum channel gain user. Besides, the proposed algorithm divides the subcarriers into two groups according to the standard deviation of the channel gain of each subcarrier. Then, it gives the priority to the group with low standard deviation values during subcarrier-user allocation to guarantee a high difference in channel-gain between the paired users per subcarrier. Later, fractional transmit power allocation is applied to distribute the subcarrier power between the paired users. Simulation results prove that the proposed algorithm improves the spectral efficiency of the system, and guarantees a significantly higher difference in channel-gain between the paired users per subcarrier compared to the conventional algorithms.