Nonorthogonal Multiple Access (NOMA): How It Meets 5G and Beyond

Abstract

Due to massive connectivity and increasing demands of various services and data‐hungry applications, a full‐scale implementation of the fifth‐generation (5G) wireless systems requires more effective radio access techniques. In this regard, nonorthogonal multiple access (NOMA) has recently gained ever‐growing attention from both academia and industry. Compared to orthogonal multiple access (OMA) techniques, NOMA is superior in terms of spectral efficiency and is thus appropriate for 5G and beyond. In this article, we provide an overview of NOMA principles and applications. Specifically, the article discusses the fundamentals of power‐domain NOMA with single and multiple antennas in both uplink and downlink settings. In addition, the basic principles of code‐domain NOMA are elaborated. Further, the article explains various resource allocation techniques such as user pairing and power allocation for NOMA systems; discusses the basic form of cooperative NOMA and its variants; and addresses several opportunities and challenges associated with the compatibility of NOMA with other advanced communication paradigms such as heterogeneous networks and millimeter wave communications.

LPWAN Technologies: Emerging Application Characteristics, Requirements, and Design Considerations

“…In situations with a large number of devices and densification, as well as strong and efficient multi access techniques, are needed owing to limited air resource issues and the potential for cross-technology interference. A possible multi-access approach can be non-orthogonal multiple access (NOMA) [10]. It may be noted that NOMA is also being considered for 5G access networks.…”

“…Moreover, SDR is considered one of the key technologies that enable the use of optimized spectrum access. The adoption of integrated circuit (IC) technologies and low-complexity transceiver structures, such as the direct-conversion radio (DCR) architecture [10], result in manufacturing efficiency. DCR requires neither external intermediate frequency filters nor the image rejection filter.…”

“…Proprietary and standards-based LPWAN technologies have different strengths and weaknesses in terms of operations, co-existence, and interworking with each other. There are different challenges for the technologies operating in unlicensed and licensed bands [10]. For unlicensed bands, flexibility and faster time to market are major advantages.…”

Subcarrier-User Assignment in Downlink NOMA for Improving Spectral Efficiency and Fairness

“…Next, the signal sent from the BS to the users paired on the subcarrier s is represented by [1]- [2], and [6]- [8]:…”

“…Due to the enormous demands of various services and fast growth of the mobile Internet and the Internet of Things (IoT) applications, the achievement of the fifth-generation (5G) and beyond-5G wireless system is expected to turn out by 2020s [1], and [2]. Non-orthogonal multiple access (NOMA) is a necessity to empower technology for beyond-5G wireless networks.…”