The article "Application of Non-orthogonal Multiple Access in LTE and 5G Networks" by Zhiguo Ding, Yuanwei Liu, Jinho Choi, Qi Sun, Maged Elkashlan, Chih-Lin I, and H. Vincent Poor provides a comprehensive overview of non-orthogonal multiple access (NOMA) technology, its key features, and its integration into 3GPP Long Term Evolution (LTE) and 5th generation (5G) mobile networks. NOMA is a promising multiple access technique that enhances spectral efficiency by allowing multiple users to share the same frequency, time, and code resources but with different power levels. This approach significantly improves spectral efficiency compared to conventional orthogonal multiple access (OMA) by enabling users with poor channel conditions to access all subcarrier channels, while users with strong channel conditions can still benefit from higher transmission power. The article covers various aspects of NOMA, including its combination with multiple-input multiple-output (MIMO) technologies, cooperative NOMA, and the interplay between NOMA and cognitive radio. It also reviews the standardization efforts and research challenges in implementing NOMA in LTE and 5G networks. Key topics include: 1. **NOMA Basics**: Introduces the fundamental concepts of NOMA, such as power allocation policies, successive interference cancellation (SIC), and the relationship between NOMA and conventional information theoretic concepts. 2. **Downlink and Uplink NOMA**: Discusses the performance gains of NOMA over OMA in terms of sum rate and the trade-offs between system throughput and user fairness. 3. **MIMO NOMA Transmission**: Explores the extension of NOMA to MIMO systems, including beamforming and spatial multiplexing, and their impact on spectral efficiency and complexity. 4. **Cooperative NOMA Transmission**: Describes how users with stronger channel conditions can act as relays to improve the reception reliability of users with weaker channel conditions. 5. **Interplay Between Cognitive Radio and NOMA**: Highlights the analogy between NOMA and cognitive radio, and how this relationship can be leveraged to improve system performance and user connectivity. 6. **State of the Art for NOMA in 3GPP LTE and 5G**: Reviews the ongoing standardization efforts, including the MUST study item and other non-orthogonal multiple access schemes like sparse code multiple access (SCMA), pattern division multiple access (PDMA), and multiuser shared multiple access (MUSA). 7. **Research Challenges**: Identifies key research areas such as user pairing/clustering, hybrid multiple access, MIMO-NOMA, imperfect channel state information (CSI), and cross-layer optimization. The article concludes by emphasizing the importance of NOMA in enhancing the performance and efficiency of future mobile networks, while also highlighting the ongoing challenges and potential solutions in its implementation.The article "Application of Non-orthogonal Multiple Access in LTE and 5G Networks" by Zhiguo Ding, Yuanwei Liu, Jinho Choi, Qi Sun, Maged Elkashlan, Chih-Lin I, and H. Vincent Poor provides a comprehensive overview of non-orthogonal multiple access (NOMA) technology, its key features, and its integration into 3GPP Long Term Evolution (LTE) and 5th generation (5G) mobile networks. NOMA is a promising multiple access technique that enhances spectral efficiency by allowing multiple users to share the same frequency, time, and code resources but with different power levels. This approach significantly improves spectral efficiency compared to conventional orthogonal multiple access (OMA) by enabling users with poor channel conditions to access all subcarrier channels, while users with strong channel conditions can still benefit from higher transmission power. The article covers various aspects of NOMA, including its combination with multiple-input multiple-output (MIMO) technologies, cooperative NOMA, and the interplay between NOMA and cognitive radio. It also reviews the standardization efforts and research challenges in implementing NOMA in LTE and 5G networks. Key topics include: 1. **NOMA Basics**: Introduces the fundamental concepts of NOMA, such as power allocation policies, successive interference cancellation (SIC), and the relationship between NOMA and conventional information theoretic concepts. 2. **Downlink and Uplink NOMA**: Discusses the performance gains of NOMA over OMA in terms of sum rate and the trade-offs between system throughput and user fairness. 3. **MIMO NOMA Transmission**: Explores the extension of NOMA to MIMO systems, including beamforming and spatial multiplexing, and their impact on spectral efficiency and complexity. 4. **Cooperative NOMA Transmission**: Describes how users with stronger channel conditions can act as relays to improve the reception reliability of users with weaker channel conditions. 5. **Interplay Between Cognitive Radio and NOMA**: Highlights the analogy between NOMA and cognitive radio, and how this relationship can be leveraged to improve system performance and user connectivity. 6. **State of the Art for NOMA in 3GPP LTE and 5G**: Reviews the ongoing standardization efforts, including the MUST study item and other non-orthogonal multiple access schemes like sparse code multiple access (SCMA), pattern division multiple access (PDMA), and multiuser shared multiple access (MUSA). 7. **Research Challenges**: Identifies key research areas such as user pairing/clustering, hybrid multiple access, MIMO-NOMA, imperfect channel state information (CSI), and cross-layer optimization. The article concludes by emphasizing the importance of NOMA in enhancing the performance and efficiency of future mobile networks, while also highlighting the ongoing challenges and potential solutions in its implementation.