A Tutorial on Nonorthogonal Multiple Access for 5G and Beyond

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 tomultiple inputmultiple 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.Comment: 25 pages, 10 figure

A novel spectrum sharing scheme assisted by secondary NOMA relay

In this letter, a two-slot secondary non-orthogonal multiple access (NOMA) relay is used to assist spectrum sharing, where the primary transceivers with long distance communicate through the relay. First, the information for the primary receiver (PR) and secondary receivers (SRs) is transmitted via the NOMA relay. Then, the information for PR is re-transmitted to it through a selected SR to improve its quality of service using maximal-ratio combining, while the next data for PR is sent from the primary transmitter (PT) to the NOMA relay simultaneously. The power allocation solution is derived for the NOMA relay. Simulation results have shown the effectiveness of the proposed scheme

Performance gap of two users in downlink full-duplex cooperative NOMA

A full-duplex non-orthogonal multiple access (FD-NOMA) systems are expected to play a significant role in fifth generation (5G) networks, addressing spectrum efficiency and massive connections. In this regard, the feasibility of FD communications to improve spectrum utilization is main consideration in term of outage performance. Specifically, we derive exact formulas of outage probability for FD-NOMA, over Nakagami-m fading channels. Extensive analysis revealed that higher quality of channel leads to better performance. We verify expressions throughout Monte-Carlo simulations

Energy-efficient non-orthogonal multiple access for wireless communication system

Non-orthogonal multiple access (NOMA) has been recognized as a potential solution for enhancing the throughput of next-generation wireless communications. NOMA is a potential option for 5G networks due to its superiority in providing better spectrum efficiency (SE) compared to orthogonal multiple access (OMA). From the perspective of green communication, energy efficiency (EE) has become a new performance indicator. A systematic literature review is conducted to investigate the available energy efficient approach researchers have employed in NOMA. We identified 19 subcategories related to EE in NOMA out of 108 publications where 92 publications are from the IEEE website. To help the reader comprehend, a summary for each category is explained and elaborated in detail. From the literature review, it had been observed that NOMA can enhance the EE of wireless communication systems. At the end of this survey, future research particularly in machine learning algorithms such as reinforcement learning (RL) and deep reinforcement learning (DRL) for NOMA are also discussed