State of the Art, Taxonomy, and Open Issues on Cognitive Radio Networks with NOMA

Abstract

The explosive growth of mobile devices and the rapid increase of wideband wireless services call for advanced communication techniques that can achieve high spectral efficiency and meet the massive connectivity requirement. Cognitive radio (CR) and non-orthogonal multiple access (NOMA) are envisioned to be important solutions for the fifth generation wireless networks. Integrating NOMA techniques into CR networks (CRNs) has the tremendous potential to improve spectral efficiency and increase the system capacity. However, there are many technical challenges due to the severe interference caused by using NOMA. Many efforts have been made to facilitate the application of NOMA into CRNs and to investigate the performance of CRNs with NOMA. This article aims to survey the latest research results along this direction. A taxonomy is devised to categorize the literature based on operation paradigms, enabling techniques, design objectives and optimization characteristics. Moreover, the key challenges are outlined to provide guidelines for the domain researchers and designers to realize CRNs with NOMA. Finally, the open issues are discussed.Cognitive radio, non-orthogonal multiple access, spectral efficiency, massive connectivity. I. INTRODUCTIONT HE explosive growth of mobile devices, the rapidly increasing demand on the broadband and highrate communication services, such as augmented reality (AR) and virtual reality (VR), and the fixed spectrum assignment policy result in the increasingly severe spectrum scarcity problem. According to the third Generation Partnership Project (3GPP), compared with the fourth generation (4G) networks, the fifth generation (5G) networks are required to achieve 1000 times higher system capacity, 10 times higher spectral efficiency (SE), and 100 times higher connectivity density [1]. Moreover, among these requirements, meeting the system capacity is the most important but probably the most challenging one due to the limited spectrum resource. Thus, it is imperative to develop advanced communication techniques that can achieve high SE as well as massive wireless connectivity. As a promising technique, cognitive radio (CR) has drawn significant attention in both industry and academia due to its high SE [2]. It can enable the secondary network (or called the unlicensed network) to access the licensed frequency bands of the primary network by using adaptive transmission strategies while protecting the quality-of-service (QoS) of the primary one.Besides CR, non-orthogonal multiple access (NOMA) techniques are promising to improve SE and user connectivity density [4], [5]. Unlike the conventional orthogonal multiple access (OMA) techniques, NOMA techniques allow multiple users simultaneously access the network at the same time and the same frequency band by using non-orthogonal resources, such as different power levels or low-density spreading codes. In [5], the authors have classified the existing dominant NOMA schemes into two categories based on the non-orthogonality resources, namely, power-...

Outage analysis of SWIPT‐based full‐duplex cognitive NOMA downlink system over Nakagami‐m fading channels

“…17 Although its benefits, the performance of the cognitive radio network with NOMA is strictly limited due to the interferences. 18 Cognitive radio is interference-limited due to the coexistence of primary and secondary networks, and power domain NOMA has intra-network interference as symbols are superposition coded. So it is crucial to use cognitive-NOMA in an applicable manner to minimize interference and better exploitation of spectrum resources.…”

“…Case 1 (Absence of interference from SS for T duration). Applying the noise-limited constraint to the received SINR given in (3) and (4), (18) can be rewritten as…”

“…As both NOMA and cognitive radio target efficient spectrum utilization, the combination of NOMA and cognitive radio has shown the prospect to achieve high throughput, massive connectivity, and low latency in 5G networks . Although its benefits, the performance of the cognitive radio network with NOMA is strictly limited due to the interferences . Cognitive radio is interference‐limited due to the coexistence of primary and secondary networks, and power domain NOMA has intra‐network interference as symbols are superposition coded.…”

Edge computing and power control in NOMA‐enabled cognitive radio networks

“…With the rapid development of wireless networks, devices accessing the network have experienced exponential growth. The increase of access devices leads to a shortage of spectrum resources and growth of mobile data traffic . However, traditional wireless cellular networks are not able to meet the requirements of higher data rate, more intensive computational capability, and more efficient spectrum utilization .…”

“…The increase of access devices leads to a shortage of spectrum resources and growth of mobile data traffic. 1 However, traditional wireless cellular networks are not able to meet the requirements of higher data rate, more intensive computational capability, and more efficient spectrum utilization. 2 Therefore, researchers are urgently required to propose practical techniques to solve the above problems.…”