BEST READINGS

Overview

• Clerckx, Bruno, et al. "Multiple Access Techniques for Intelligent and Multi-Functional 6G: Tutorial, Survey, and Outlook," in Proceedings of the IEEE, 2024.

Multiple access (MA) is a crucial part of any wireless system and refers to techniques that make use of the resource dimensions to serve multiple users/devices/machines/services, ideally in the most efficient way. Given the needs of multi-functional wireless networks for integrated communications, sensing, localization, computing, coupled with the surge of machine learning / artificial intelligence (AI) in wireless networks, MA techniques are expected to experience a paradigm shift in 6G and beyond. In this paper, the authors provide a tutorial, survey and outlook of past, emerging and future MA techniques and pay a particular attention to how wireless network intelligence and multi-functionality will lead to a re-thinking of those techniques.

• B. Clerckx, H. Joudeh, C. Hao, M. Dai, and B. Rassouli, "Rate splitting for MIMO wireless networks: a promising PHY-layer strategy for LTE evolution," in IEEE Communications Magazine, vol. 54, no. 5, pp. 98-105, May 2016.

This paper proposes the 1-layer rate-splitting model for multi-antenna broadcast channels.

• B. Clerckx et al., "A Primer on Rate-Splitting Multiple Access: Tutorial, Myths, and Frequently Asked Questions," in IEEE Journal on Selected Areas in Communications. 

In this tutorial, the authors depart from the orthogonal multiple access (OMA) versus non-orthogonal multiple access (NOMA) discussion held in 5G, and the conventional multi-user linear precoding approach used in space-division multiple access (SDMA), multi-user and massive MIMO in 4G and 5G, and show how multi-user communications and multiple access design for 6G and beyond should be intimately related to the fundamental problem of interference management. The authors start from foundational principles of interference management and rate-splitting, and progressively delineate RSMA frameworks for downlink, uplink, and multi-cell networks. 

• Y. Mao, O. Dizdar, B. Clerckx, R. Schober, P. Popovski and H. V. Poor, "Rate-Splitting Multiple Access: Fundamentals, Survey, and Future Research Trends," in IEEE Communications Surveys & Tutorials, 2022.

This paper presents the first comprehensive tutorial on RSMA providing a survey of the pertinent state-of-the-art research, detailing its architecture, taxonomy, and various appealing applications, as well as comparing with existing MA schemes in terms of their overall frameworks, performance, and complexities. An in-depth discussion of future RSMA research challenges is also provided to inspire future research on RSMA-aided wireless communication for beyond 5G systems. 

• A. Mishra, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part I: Principles, Applications and Future Works," in IEEE Communications Letters, 2022.

This letter is the first part of a three-part tutorial focusing on rate-splitting multiple access (RSMA) for 6G. As Part I of the tutorial, the letter presents the basics of RSMA and its applications in light of 6G. The letter delineates the design principle and basic transmission frameworks of downlink and uplink RSMA. The letter then illustrates the applications of RSMA for addressing the challenges of various potential enabling technologies and use cases, consequently making it a promising next generation multiple access (NGMA) scheme for future networks such as 6G and beyond.  

• L. Yin, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part II: Interplay with Integrated Sensing and Communications," in IEEE Communications Letters, 2022.

This letter is the second part of a three-part tutorial focusing on rate-splitting multiple access (RSMA) for 6G. As Part II of the tutorial, this letter addresses the interplay between RSMA and integrated radar sensing and communications (ISAC). In particular, the introduces a general RSMA-assisted ISAC architecture, where the ISAC platform has a dual capability to simultaneously communicate with downlink users and probe detection signals to a moving target.  

• H. Li, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part III: Interplay with Reconfigurable Intelligent Surfaces," in IEEE Communications Letters, 2022. 

This letter is the third part of a three-part tutorial that focuses on rate-splitting multiple access (RSMA) for 6G. As Part III of the tutorial, this letter provides an overview of integrating RSMA and reconfigurable intelligent surface (RIS). 

Sum-Rate Optimization

• H. Joudeh and B. Clerckx, "Sum-rate maximization for linearly precoded downlink multiuser MISO systems with partial CSIT: A rate-splitting approach," in IEEE Transactions on Communications, vol. 64, no. 11, pp. 4847-4861, Nov. 2016.

This is the first paper that studies the performance of rate-splitting with partial CSIT and it proves that rate-splitting achieves the optimal sum-Degree-of-Freedom (DoF) of multiple-input single-output (MISO) broadcast channel (BC) with imperfect channel state information at the transmitter (CSIT).

• A. Mishra, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for Downlink Multiuser MIMO: Precoder Optimization and PHY-Layer Design," IEEE Transactions on Communications, vol. 70, no. 2, pp. 874-890, Feb. 2022.

This is the first paper that compares the DoF of MU–MIMO, MIMO NOMA and RS in a MIMO setting, studies the precoder optimization and the benefits of transmitting multiple commons streams in RS-assisted MIMO BC with perfect and imperfect CSIT, and designs the PHY-layer architecture to provide throughput performance of RS via the link level simulations (LLS) in MIMO settings. 

RSMA Generalizes NOMA and SDMA

• Y. Mao, B. Clerckx, and V.O.K. Li, "Rate-splitting multiple access for downlink communication systems: bridging, generalizing, and outperforming SDMA and NOMA," EURASIP Journal on Wireless Communications and Networking, 133 (2018). 

This is the first paper that proposes the generalized framework of RSMA and compares its performance with non-orthogonal multiple access (NOMA) and dirty paper coding (DPC).

• B. Clerckx, Y. Mao, R. Schober and H. V. Poor, "Rate-splitting unifying SDMA, OMA, NOMA, and multicasting in MISO broadcast channel: A simple two-user rate analysis," in IEEE Wireless Communications Letters, vol. 9, no. 3, pp. 349-353, March 2020.

This paper illustrates the simplest two-user rate-splitting in MISO broadcast channel. Low-complexity precoding based on zero-forcing is adopted and the optimal power allocation between the common and private streams is calculated.

Next Generation Multiple Access

• A. Mishra, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part I: Principles, Applications and Future Works," in IEEE Communications Letters, 2022.

This letter is the first part of a three-part tutorial focusing on rate-splitting multiple access (RSMA) for 6G. As Part I of the tutorial, the letter presents the basics of RSMA and its applications in light of 6G. The letter delineates the design principle and basic transmission frameworks of downlink and uplink RSMA. The letter then illustrates the applications of RSMA for addressing the challenges of various potential enabling technologies and use cases, consequently making it a promising next generation multiple access (NGMA) scheme for future networks such as 6G and beyond.   

• B. Clerckx, Y. Mao, R. Schober, E. Jorswieck, D. J. Love, J. Yuan, L. Hanzo, G. Y. Li, E. G. Larsson, and G. Caire., "Is NOMA efficient in multi-antenna networks? A critical look at next generation multiple access techniques," in IEEE Open Journal of the Communications Society, vol. 2, pp. 1310-1343, 2021.

This paper shows why non-orthogonal multiple access (NOMA) is inefficient in multi-antenna settings based on basic multiplexing gain analysis and highlights other non-orthogonal transmission frameworks, such as rate-splitting, exist which fully exploit the multiplexing gain and the benefits of successice interference cancellation (SIC) to boost the rate in multi-antenna settings.

• Clerckx, Bruno, et al. "Multiple Access Techniques for Intelligent and Multi-Functional 6G: Tutorial, Survey, and Outlook." arXiv preprint arXiv:2401.01433 (2024).

Multiple access (MA) is a crucial part of any wireless system and refers to techniques that make use of the resource dimensions to serve multiple users/devices/machines/services, ideally in the most efficient way. Given the needs of multi-functional wireless networks for integrated communications, sensing, localization, computing, coupled with the surge of machine learning / artificial intelligence (AI) in wireless networks, MA techniques are expected to experience a paradigm shift in 6G and beyond. In this paper, the authors provide a tutorial, survey and outlook of past, emerging and future MA techniques and pay a particular attention to how wireless network intelligence and multi-functionality will lead to a re-thinking of those techniques.

Beyond Dirty Paper Coding

• Y. Mao and B. Clerckx, "Beyond dirty paper coding for multi-antenna broadcast channel with partial CSIT: A rate-splitting approach," in IEEE Transactions on Communications, vol. 68, no. 11, pp. 6775-6791, Nov. 2020, doi: 10.1109/TCOMM.2020.3014153.

This is the first paper that shows that linearly precoded RSMA outperforms DPC with partial CSIT. A novel non-linear RSMA strategy, namely, dirty paper coded rate splitting (DPCRS) is proposed and shown to achieve a better rate region than DPC. 

Two-user Interference Channel

• T. Han and K. Kobayashi, "A new achievable rate region for the interference channel," in IEEE Transactions on Information Theory, vol. 27, no. 1, pp. 49-60, January 1981.

It proposes rate-splitting for two-user single-input single-output (SISO) interference channel (IC).

• R. H. Etkin, D. N. C. Tse and H. Wang, "Gaussian interference channel capacity to within one bit," in IEEE Transactions on Information Theory, vol. 54, no. 12, pp. 5534-5562, Dec. 2008.

This work shows that rate-splitting based on the HK scheme achieves rate regions within 1 bit/s/Hz of the capacity region in SISO IC.

Multiple Access Channel (Uplink)

• B. Rimoldi and R. Urbanke, "A rate-splitting approach to the Gaussian multiple-access channel," in IEEE Transactions on Information Theory, vol. 42, no. 2, pp. 364-375, March 1996.

This is the first work of rate-splitting in the uplink. It shows that rate-splitting based on successive single-user decoding and interference cancellation achieves the capacity region of the K-user Gaussian multiple access channel without the need for time sharing.

Two-User MISO BC with Partial CSIT

• S. Yang, M. Kobayashi, D. Gesbert and X. Yi, "Degrees of freedom of time correlated MISO broadcast channel with delayed CSIT," in IEEE Transactions on Information Theory, vol. 59, no. 1, pp. 315-328, Jan. 2013.

     This work calculates the two-user DoF for MISO BC with imperfect CSIT.

• S. Yang and Z. Lit, "A constant-gap result on the multi-antenna broadcast channels with linearly precoded rate splitting," IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Kalamata, 2018.

     This work calculates the two-user achieves constant-gap optimal to the sum-capacity of the two-user MISO BC. 

• Z. Li and S. Yang, "A linearly precoded rate splitting approach and its optimality for MIMO broadcast channels," IEEE Information Theory Workshop (ITW), Guangzhou, 2018.

This paper shows rate-splitting achieves constant-gap optimal to the whole capacity region of the two-user MISO BC. But the constant-gap optimality is not guaranteed in general. 

Sum-GDoF of the K-User Underloaded MISO BC with Partial CSIT

• A. Gholami Davoodi and S. A. Jafar, "Transmitter cooperation under finite precision CSIT: A GDoF perspective," in IEEE Transactions on Information Theory, vol. 63, no. 9, pp. 6020-6030, Sept. 2017.

This work proves that rate-splitting-assisted interference enhancement approach achieves the entire generalized DoFs (GDoFs) region of the two-user underloaded MISO BC with imperfect CSIT.

Sum-DoF Optimality of K-user MISO BC with Partial CSIT

• A. Gholami Davoodi and S. A. Jafar, "Aligned image sets under channel uncertainty: settling conjectures on the collapse of degrees of freedom under finite precision CSIT," in IEEE Transactions on Information Theory, vol. 62, no. 10, pp. 5603-5618, Oct. 2016.

This work provides a tight sum-DoF upperbound for the K-user MISO BC with arbitrary levels of partial CSIT.

• H. Joudeh and B. Clerckx, "Sum-rate maximization for linearly precoded downlink multiuser MISO systems with partial CSIT: A rate-splitting approach," in IEEE Transactions on Communications, vol. 64, no. 11, pp. 4847-4861, Nov. 2016.

RS achieves the optimum sum-DoF of the K-user underloaded MISO BC with imperfect CSIT, which coincides with the sum-DoF upperbound shown in the previous paper (Davoodi and Jafar, TIT, 2016).

DoF Region Optimality of K-user MISO BC with Partial CSIT

• E. Piovano and B. Clerckx, "Optimal DoF region of the K-user MISO BC with partial CSIT," in IEEE Communications Letters, vol. 21, no. 11, pp. 2368-2371, Nov. 2017.

This work proves that RS achieves the entire DoF region of the underloaded MISO BC with imperfect CSIT.

• H. Joudeh and B. Clerckx, "DoF region of the MISO BC with partial CSIT: Proof by inductive Fourier-Motzkin elimination," IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Cannes, France, 2019.

This work proposes an alternative approach to prove the optimality of the DoF region achieved by rate-splitting.

Symmetric DoF of K-user MISO BC with Partial CSIT

• H. Joudeh and B. Clerckx, "Robust transmission in downlink multiuser MISO systems: A rate-splitting approach," in IEEE Transactions on Signal Processing, vol. 64, no. 23, pp. 6227-6242, 1 Dec.1, 2016.

This work shows that rate-splitting achieves a higher symmetric (max-min) DoF than space division multiple access (SDMA) based on multi-user linear precoding for the K-user underloaded MISO BC with imperfect CSIT.

Overloaded Transmission

• E. Piovano, H. Joudeh and B. Clerckx, "Overloaded multiuser MISO transmission with imperfect CSIT," 50th Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, 2016.

This work proves that rate-splitting achieves the entire DoF region of the K-user overloaded MISO BC with imperfect heterogeneous CSIT qualities.

Multi-Antenna Wireless Networks

• C. Hao and B. Clerckx, "MISO networks with imperfect CSIT: A topological rate-splitting approach," in IEEE Transactions on Communications, vol. 65, no. 5, pp. 2164-2179, May 2017.

This work calculates DoF region of rate-splitting for the K-cell MISO IC with imperfect CSIT.

DoF Optimality for MIMO Networks

• C. Hao, B. Rassouli and B. Clerckx, "Achievable DoF regions of MIMO networks with imperfect CSIT," in IEEE Transactions on Information Theory, vol. 63, no. 10, pp. 6587-6606, Oct. 2017.

This work proposes an achievable scheme based on rate-splitting for the two-user multiple input multiple output (MIMO) networks with imperfect CSIT, and shows optimality under certain antenna-configurations and CSIT qualities.

• A. Gholami Davoodi and S. Jafar, "Degrees of Freedom Region of the (M, N₁, N₂) MIMO Broadcast Channel With Partial CSIT: An Application of Sum-Set Inequalities Based on Aligned Image Sets," in IEEE Transactions on Information Theory, vol. 66, no. 10, pp. 6256-6279, Oct. 2020.

This work derives the upperbound of the DoF region of the two-user MIMO networks with imperfect CSIT and shows the DoF region of rate-splitting achieved by the previous paper (Hao et al. TIT 2017) coincides with the upperbound.

Symmetric DoF in Multigroup Multicast Transmission

• H. Joudeh and B. Clerckx, "Rate-splitting for max-min fair multigroup multicast beamforming in overloaded systems," in IEEE Transactions on Wireless Communications, vol. 16, no. 11, pp. 7276-7289, Nov. 2017.

This work shows that rate-splitting achieves the highest symmetric DoF compared with that of SDMA based on MU-LP and NOMA based on superposition coding (SC) and successive interference cancellation (SIC) for the K-user overloaded MISO BC with perfect CSIT.

• L. Yin and B. Clerckx, "Rate-splitting multiple access for multigroup multicast and multibeam satellite systems," in IEEE Transactions on Communications, 2020.

This paper characterizes the MMF DoF achieved by RSMA in multigroup multicast transmission with imperfect CSIT and demonstrates the benefits of RS strategies for both underloaded and overloaded scenarios.

PHY Layer Design and Link-Level Simulations

• S. Zhang, B. Clerckx , D. Vargas, O. Haffenden and A. Murphy, “Rate-Splitting Multiple Access: Finite Constellations, Receiver Design, and SIC-free Implementation,” IEEE Transactions on Communications, early access, Mar. 2024.

This paper investigate practical receiver designs and proposed SIC-free receivers for RSMA. Low complexity precoders and receivers are evaluated by both theoretical metric and link-level simulations.

• O. Dizdar, Y. Mao, W. Han and B. Clerckx, "Rate-splitting multiple access for downlink multi-antenna communications: Physical layer design and link-level simulations," 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), London, United Kingdom, 2020.

This paper designs the physical layer of RSMA, accounting for modulation, coding (using polar codes), message split, adaptive modulation and coding, and SIC receiver. 

• H. Chen, D. Mi, Z. Chu, P. Xiao, Y. Xu and D. He, "Link-level performance of rate-splitting based downlink multiuser MISO systems," IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications, London, United Kingdom, 2020.

This paper studies the uncoded link level performance of rate-splitting. Bit error rate (BER) performance of RSMA is provided.

Space-Time Coding

• C. Mosquera, N. Noels, T. Ramírez, M. Caus and A. Pastore, "Space-Time Rate Splitting for the MISO BC With Magnitude CSIT," in IEEE Transactions on Communications, vol. 69, no. 7, pp. 4417-4432, July 2021.

This paper proposes a particular RS scheme which relies on space-time block coding to transmit the common message.  The proposed scheme is shown to be suited in the absence of full CSIT.

Quantized Feedback

• C. Hao, Y. Wu and B. Clerckx, "Rate analysis of two-receiver MISO broadcast channel with finite rate feedback: A rate-splitting approach," in IEEE Transactions on Communications, vol. 63, no. 9, pp. 3232-3246, Sept. 2015.

This paper focuses on a two-user multiple-input single-output (MISO) broadcast channel (BC) with quantized channel state information at the transmitter (CSIT) (based on random vector quantization). It shows the potential of RSMA to reduce the feedback overhead.

• G. Lu, L. Li, H. Tian and F. Qian, "MMSE-based precoding for rate splitting systems with finite feedback," in IEEE Communications Letters, vol. 22, no. 3, pp. 642-645, March 2018.

This paper focuses on a K-user MISO BC with quantized CSIT (based on random vector quantization). Rate-splitting is shown to achieve significant sum-rate gain over conventional schemes.

Global Optimization

• B. Matthiesen, Y. Mao, A. Dekorsy, P. Popovski, and B. Clerckx, "Globally optimal spectrum- and energy-efficient beamforming for rate splitting multiple access," arXiv:2204.00273 (2022). [arXiv]

• B. Matthiesen, Y. Mao, P. Popovski and B. Clerckx, "Globally optimal beamforming for rate splitting multiple access," IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2021, pp. 4775-4779. [Poster and Presentation]

This work considers globally optimal precoder design for RSMA in Gaussian MISO downlink channels with respect to weighted sum rate and energy efficiency maximization. 

Energy Efficiency Optimization

• Y. Mao, B. Clerckx and V. O. K. Li, "Energy efficiency of rate-splitting multiple access, and performance benefits over SDMA and NOMA," 15th International Symposium on Wireless Communication Systems (ISWCS), Lisbon, 2018.

This is the first paper that shows the energy efficiency performance of RSMA. 

• G. Zhou, Y. Mao, and B. Clerckx, "Rate-splitting multiple access for multi-antenna downlink communication systems: spectral and energy efficiency tradeoff," arXiv preprint arXiv:2001.03206, 2020.

This paper shows that RSMA achieves a superior trade-off between spectral and energy efficiency than SDMA and NOMA.

Robust Optimization

• H. Joudeh and B. Clerckx, "Robust transmission in downlink multiuser MISO systems: A rate-splitting approach," in IEEE Transactions on Signal Processing, vol. 64, no. 23, pp. 6227-6242, Dec. 2016.

This work shows that RS achieves higher max-min (symmetric) Degree-of-Freedom (DoF) compared with conventional SDMA based on MU-LP for CSIT uncertainty regions that scale with SNR (e.g., by scaling the number of feedback bits). For the special case of non-scaling CSIT (e.g., fixed number of feedback bits), RS achieves a non-saturating max-min rate which is contrary to MU-LP. 

• M. Medra and T. N. Davidson, "Robust downlink transmission: An offset-based single-rate-splitting approach," IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Kalamata, 2018.

This is the first paper that studies the performance of rate-splitting with partial CSIT and it proves rate-splitting achieves the optimal sum-DoF of MISO BC with imperfect CSIT.

Joint Decoding Receiver

• Z. Li, C. Ye, Y. Cui, S. Yang and S. Shamai, "Rate splitting for multi-antenna downlink: precoder design and practical implementation," in IEEE Journal on Selected Areas in Communications, vol. 38, no. 8, pp. 1910-1924, Aug. 2020.

This paper investigates the achievable rates of RSMA in MISO BC with imperfect CSIT with joint decoding receivers. 

Multi-User Multi-Antenna Communications

• Y. Mao, B. Clerckx, and V.O.K. Li, "Rate-splitting multiple access for downlink communication systems: bridging, generalizing, and outperforming SDMA and NOMA," EURASIP Journal on Wireless Communications and Networking, 133 (2018). https://doi.org/10.1186/s13638-018-1104-7

This is the first paper that proposes the generalized framework of RSMA and compares its performance with non-orthogonal multiple access (NOMA) and dirty paper coding (DPC).

• B. Clerckx, Y. Mao, R. Schober and H. V. Poor, "Rate-splitting unifying SDMA, OMA, NOMA, and multicasting in MISO broadcast channel: A simple two-user rate analysis," in IEEE Wireless Communications Letters, vol. 9, no. 3, pp. 349-353, March 2020.

This paper illustrates the simplest two-user rate-splitting in MISO broadcast channel. Low-complexity precoding based on zero-forcing is adopted and the optimal power allocation between the common and private streams is calculated.

• A. Mishra, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for Downlink Multiuser MIMO: Precoder Optimization and PHY-Layer Design, " IEEE Transactions on Communications, vol. 70, no. 2, pp. 874-890, Feb. 2022.

This is the first paper that compares the DoF of MU–MIMO, MIMO NOMA and RS in a MIMO setting, studies the precoder optimization and the benefits of transmitting multiple commons streams in RS-assisted MIMO BC with perfect and imperfect CSIT, and designs the PHY-layer architecture to provide throughput performance of RS via the link level simulations (LLS) in MIMO settings.  

• Z. Yang, M. Chen, W. Saad, and M. Shikh-Bahaei. "Optimization of rate allocation and power control for rate splitting multiple access (RSMA)." arXiv preprint arXiv:1903.08068, 2019.

This paper studies the sum-rate maximization problem of RSMA in SISO BC.

Multigroup Multicast

• H. Joudeh and B. Clerckx, "Rate-splitting for max-min fair multigroup multicast beamforming in overloaded systems," in IEEE Transactions on Wireless Communications, vol. 16, no. 11, pp. 7276-7289, Nov. 2017.

This is the first paper of RSMA in multigroup multicast transmission. This work characterizes the max-min fairness (MMF) DoF achieved by RSMA in multigroup multicast with perfect CSIT. It also shows that RS exhibits strictly higher MMF-rates in partially and fully overloaded scenarios.

• Yalcin, Ahmet Zahid, Mustafa Kagan Cetin, and Melda Yuksel. "Max-min fair precoder design and power allocation for MU-MIMO NOMA." arXiv preprint arXiv:1911.09402, 2019.

This paper illustrates the MMF gain of RSMA over SDMA and NOMA in multigroup multicasting scenarios.

Energy Efficiency Optimization

• Y. Mao, B. Clerckx and V. O. K. Li, "Energy efficiency of rate-splitting multiple access, and performance benefits over SDMA and NOMA," 15th International Symposium on Wireless Communication Systems (ISWCS), Lisbon, 2018.

This is the first paper that shows the energy efficiency performance of RSMA. 

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting for multi-antenna non-orthogonal unicast and multicast transmission: Spectral and energy efficiency analysis," in IEEE Transactions on Communications, vol. 67, no. 12, pp. 8754-8770, Dec. 2019.

This is the first paper investigating RSMA in NOUM. A novel system model based on RSMA is proposed for NOUM which better reuses the SIC for the dual purpose of separating the unicast and multicast streams as well as better managing the multi-user.

• A. Rahmati, Y. Yapici, N. Rupasinghe, I. Guvenc, H. Dai and A. Bhuyan, "Energy efficiency of RSMA and NOMA in cellular-connected mmWave UAV networks," IEEE International Conference on Communications (ICC), Shanghai, China, 2019.

This paper investigates the energy efficiency of the RSMA and NOMA schemes in a millimeter-wave (mmWave) downlink UAV-assisted network. Numerical results indicates that RSMA is superior to NOMA in terms of overall energy efficiency.

Coordinated Multi-Point (CoMP)

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting multiple access for coordinated multi-point joint transmission," IEEE International Conference on Communications (ICC), Shanghai, China, 2019, pp. 1-6.

This is the first paper that studies RSMA in multi-cell networks. Specifically, it studies RSMA in downlink coordinated multi-point (CoMP) joint transmission (JT) networks and shows that RSMA outperforms SDMA and NOMA in a wide range of inter-user and inter-cell channel strength disparities.

Nou-Orthogonal Unicast and Multicast (NOUM) Transmission

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting for multi-antenna non-orthogonal unicast and multicast transmission: Spectral and energy efficiency analysis," in IEEE Transactions on Communications, vol. 67, no. 12, pp. 8754-8770, Dec. 2019.

This is the first paper investigating RSMA in NOUM. A novel system model based on RSMA is proposed for NOUM which better reuses the SIC for the dual purpose of separating the unicast and multicast streams as well as better managing the multi-user.

• Y. Mao, and B. Clerckx, "Dirty paper coded rate-splitting for non-orthogonal unicast and multicast transmission with partial CSIT," arXiv preprint arXiv:2012.07542, 2020.

This paper investigates non-linear precoding of RSMA in NOUM. A novel dirty paper coded rate splitting (DPCRS) strategy is proposed, which achieves larger rate regions than DPC-assisted NOUM in MISO BC with partial CSIT.

Reconfigurable Intelligent Surface (RIS)

• Z. Yang, J. Shi, Z. Li, M. Chen, W. Xu and M. Shikh-Bahaei, "Energy efficient rate splitting multiple access (RSMA) with reconfigurable intelligent surface," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This is the first paper of RSMA for RIS, in which RSMA is shown to enhance the energy efficiency of RIS-assisted transmission networks.

Simultaneous Wireless Information and Power Transfer (SWIPT)

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting for multi-user multi-antenna wireless information and power transfer," IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Cannes, France, 2019.

This paper shows that rate-splitting achieves a better rate-energy tradeoff in MISO SWIPT BC with separated information users and energy users. 

Cooperative Transmission with User Relaying

• J. Zhang, B. Clerckx, J. Ge and Y. Mao, "Cooperative rate splitting for MISO broadcast channel with user relaying, and performance benefits over cooperative NOMA," in IEEE Signal Processing Letters, vol. 26, no. 11, pp. 1678-1682.

This is the first paper that proposes cooperative rate-splitting (CRS) with user-relaying in the two-user case. 

Imperfect CSIT

• Y. Mao and B. Clerckx, "Beyond dirty paper coding for multi-antenna broadcast channel with partial CSIT: A rate-splitting approach," in IEEE Transactions on Communications, vol. 68, no. 11, pp. 6775-6791, Nov. 2020, doi: 10.1109/TCOMM.2020.3014153.

This is the first paper showing that linearly precoded RSMA outperforms DPC with partial CSIT. A novel non-linear RSMA strategy, namely, dirty paper coded rate splitting (DPCRS) is proposed and shown to achieve a better rate region than DPC. 

Link-Level Simulations

• O. Dizdar, Y. Mao, W. Han and B. Clerckx, "Rate-splitting multiple access for downlink multi-antenna communications: Physical layer design and link-level simulations," 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), London, United Kingdom, 2020.

This paper designs the physical layer of RSMA, accounting for modulation, coding (using polar codes), message split, adaptive modulation and coding, and SIC receiver. 

Cloud-Radio Access Network (C-RAN) 

• D. Yu, J. Kim and S. Park, "An efficient rate-splitting multiple access scheme for the downlink of C-RAN systems," in IEEE Wireless Communications Letters, vol. 8, no. 6, pp. 1555-1558, Dec. 2019.

This paper studies RSMA in C-RAN with fronthaul compression and fronthaul capacity constraint.

• A. Alameer Ahmad, Y. Mao, A. Sezgin, B. Clerckx, "Rate splitting multiple access in C-RAN: A scalable and robust design," arXiv preprint arXiv:2011.00076.

This paper studies RSMA in C-RAN with statistical CSIT (i.e., the transmitter only knows the distribution information of user channels).

Visible Light Communication (VLC)

• S. Tao, H. Yu, Q. Li, Y. Tang and D. Zhang, "One-layer rate-splitting multiple access with benefits over power-domain NOMA in indoor multi-cell visible light communication networks," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This is the first paper that introduces RSMA to the multi-cell visible light communication (VLC) networks. By taking into account the specific constraints of optical signals and the LED effect, 1-layer RSMA is able to enhance the system spectral efficiency.

• S. Naser et al., "Rate-splitting multiple access: unifying NOMA and SDMA in MISO VLC channels," in IEEE Open Journal of Vehicular Technology, vol. 1, pp. 393-413, 2020.

This paper provides an overview of the key multiple access techniques used in VLC systems. It also discusses the capabilities and potentials of RSMA in VLC systems. 

Secrecy Rate

• P. Li, M. Chen, Y. Mao, Z. Yang, B. Clerckx and M. Shikh-Bahaei, "Cooperative rate-splitting for secrecy sum-rate enhancement in multi-antenna broadcast channels," IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), London, United Kingdom, 2020.

This paper employs CRS technique to enhance the secrecy sum rate for the MISO BC with two legitimate users and one eavesdropper.

• H. Fu, S. Feng, W. Tang and D. W. K. Ng, "Robust secure beamforming design for two-user downlink MISO rate-splitting systems," in IEEE Transactions on Wireless Communications, vol. 19, no. 12, pp. 8351-8365, Dec. 2020.

This paper studies the max-min fairness for a downlink two-user MISO system with imperfect CSIT by taking into account a potential eavesdropper.

Aerial Networks

• A. Rahmati, Y. Yapici, N. Rupasinghe, I. Guvenc, H. Dai and A. Bhuyan, "Energy efficiency of RSMA and NOMA in cellular-connected mmWave UAV networks," IEEE International Conference on Communications (ICC), Shanghai, China, 2019.

This paper investigates energy efficiency of RSMA and NOMA in a millimeter-wave (mmWave) downlink UAV-assisted network. Numerical results indicates that RSMA is superior to NOMA in terms of overall energy efficiency.

• W. Jaafar, S. Naser, S. Muhaidat, P. C. Sofotasios and H. Yanikomeroglu, "Multiple access in aerial networks: From orthogonal and non-orthogonal to rate-splitting," in IEEE Open Journal of Vehicular Technology, vol. 1, pp. 372-392, 2020.

This paper gives a comprehensive survey of key multiple access techniques for aerial networks. It also studies RSMA in a two-user MISO BC with UAV serving as an aerial transmitter.

Imperfect CSIT and Imperfect CSIR

• J.  An,  O.  Dizdar,  B.  Clerckx,  and  W.  Shin,  “Rate-splitting  multiple access  for  multi-antenna  broadcast  channel  with  imperfect  CSIT  and CSIR,” IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), London, United Kingdom, 2020.

This paper investigates sum rate maximization of RSMA with imperfect CSIT and imperfect CSIR.

Network Performance Analysis

• E. Demarchou, C. Psomas and I. Krikidis, "Channel statistics-based rate splitting with spatial randomness," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This paper provides an analytical framework on rate-splitting which captures spatial randomness and provides closed-form expressions for the distributions of the SINR at the receivers. Results highlight the flexibility of RSMA against NOMA in terms of fairness performance.

Spectral and Energy Efficiency Tradeoff

• G. Zhou, Y. Mao, and B. Clerckx, "Rate-splitting multiple access for multi-antenna downlink communication systems: Spectral and energy efficiency tradeoff," arXiv preprint arXiv:2001.03206, 2020.

This paper shows the significant performance gains of RSMA over SDMA and NOMA in terms of energy efficiency, spectral efficiency, as well as their tradeoff in multi-antenna broadcast channels.

• J. Zhang, J. Zhang, Y. Zhou, H. Ji, J. Sun and N. Al-Dhahir, "Energy and spectral efficiency tradeoff via rate splitting and common beamforming coordination in multicell networks," in IEEE Transactions on Communications, vol. 68, no. 12, pp. 7719-7731, Dec. 2020.

This paper shows that RSMA is more flexible in achieving a better spectral and energy efficiency tradeoff than SDMA and NOMA in the multicell system.

Symbol-Level Precoding

• A. Salem, C. Masouros, and B. Clerckx. "Rate splitting with finite constellations: The benefits of interference exploitation vs suppression," arXiv preprint arXiv:1907.08457, 2019.

This paper derives new analytical expressions for the ergodic sum-rate of rate-splitting based on finite constellations with constructive interference (CI) and zero-forcing (ZF) precoding schemes for the private messages.

Millimeter-wave (mmWave)

• M. Dai and B. Clerckx, "Multiuser millimeter wave beamforming strategies with quantized and statistical CSIT," in IEEE Transactions on Wireless Communications, vol. 16, no. 11, pp. 7025-7038, Nov. 2017.

This is the first paper investigating rate-splitting in mmWave systems. This paper shows that rate-splitting enables remarkable saving in the second-stage training and feedback overhead in multi-user mmWave systems.

• A. Rahmati, Y. Yapici, N. Rupasinghe, I. Guvenc, H. Dai and A. Bhuyan, "Energy efficiency of RSMA and NOMA in cellular-connected mmWave UAV networks," IEEE International Conference on Communications (ICC), Shanghai, China, 2019.

This paper investigates the energy efficiency of RSMA and NOMA in a millimeter-wave (mmWave) downlink UAV-assisted network. Numerical results indicates that RSMA is superior to NOMA in terms of overall energy efficiency.

Massive MIMO

• M. Dai, B. Clerckx, D. Gesbert and G. Caire, "A rate splitting strategy for massive MIMO with imperfect CSIT," in IEEE Transactions on Wireless Communications, vol. 15, no. 7, pp. 4611-4624, July 2016.

This is the first paper investigating rate-splitting in massive MIMO networks.This paper proposes hierarchical rate-splitting (HRS) that is particularly suited to massive MIMO. HRS is shown to achieve significant sum rate gain in this work.

• A. Papazafeiropoulos, B. Clerckx and T. Ratnarajah, "Rate-splitting to mitigate residual transceiver hardware impairments in massive MIMO systems," in IEEE Transactions on Vehicular Technology, vol. 66, no. 9, pp. 8196-8211, Sept. 2017.

This paper shows that rate-splitting is robust to hardware imperfection resulting from oscillator phase noise and amplified thermal noise in time division duplex (TDD)-based massive MISO systems.

• A. Papazafeiropoulos and T. Ratnarajah, "Rate-splitting robustness in multi-pair massive MIMO relay systems," in IEEE Transactions on Wireless Communications, vol. 17, no. 8, pp. 5623-5636, Aug. 2018.

This paper considers a multi-pair decode-and-forward full-duplex relay channel, where the relay station is deployed with a large number of antennas. Relay stations employ a large number of antennas (massive MIMO). Rate-splitting is shown to achieve enhanced sum rate in both cases of half-duplex and full-duplex relaying.  

• O. Dizdar, Y. Mao and B. Clerckx,  "Rate-Splitting Multiple Access to Mitigate the Curse of Mobility in (Massive) MIMO Networks," in IEEE Transactions on Communications, vol. 69, no. 10, Oct. 2021.

In this work, the authors study the performance of RSMA under the important setup of imperfect Channel State Information at the Transmitter (CSIT) originating from user mobility and latency/delay (between CSI acquisition and data transmission) in the network.   

• Mishra, Anup, Yijie Mao, Christo Kurisummoottil Thomas, Luca Sanguinetti, and Bruno Clerckx, "Mitigating Intra-Cell Pilot Contamination in Massive MIMO: A Rate Splitting Approach," arXiv preprint arXiv:2206.07499 (2022).

This paper aims to integrate RSMA with TDD MaMIMO for downlink transmission and investigate its SE performance in the presence of pilot contamination. The paper shows that RSMA is significantly more robust to pilot contamination and always achieves a SE performance that is equal to or better than the conventional linearly precoded MaMIMO transmission strategy.

• A. Mishra, Y. Mao, L. Sanguinetti and B. Clerckx, "Rate-Splitting Assisted Massive Machine-Type Communications in Cell-Free Massive MIMO," IEEE Communications Letters, vol. 26, no. 6, pp. 1358-1362, June 2022.

This letter focuses on integrating RSMA with TDD Cell-free Massive MIMO for massive machine-type communications. 

Cognitive Radio

• A. Zappone, B. Matthiesen and E. A. Jorswieck, "Energy efficiency in MIMO underlay and overlay device-to-device communications and cognitive radio systems," in IEEE Transactions on Signal Processing, vol. 65, no. 4, pp. 1026-1041, 15 Feb.15, 2017.

This paper addresses the problem of resource allocation for systems in which a primary and a secondary link share the available spectrum by an underlay or overlay approach.

• Z. Lin, M. Lin, B. Champagne, W. -P. Zhu and N. Al-Dhahir, "Secure and energy efficient transmission for RSMA-based cognitive satellite-terrestrial networks," in IEEE Wireless Communications Letters.

This paper studies secure communication in RSMA-based cognitive satellite-terrestrial network (CSTN) with imperfect wiretap CSI.

Simultaneous Wireless Information and Power Transfer (SWIPT)

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting for multi-user multi-antenna wireless information and power transfer," IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Cannes, France, 2019.

This paper shows that rate-splitting achieves a better rate-energy tradeoff in MISO SWIPT BC with separated information users and energy users. 

• X. Su, L. Li, H. Yin and P. Zhang, "Robust power- and rate-splitting-based transceiver design in  K-user MISO SWIPT interference channel under imperfect CSIT," in IEEE Communications Letters, vol. 23, no. 3, pp. 514-517, March 2019.

This paper proposes a RS based robust design for MISO interference channel with SWIPT.

• M. R. Camana Acosta, C. E. G. Moreta and I. Koo, "Joint power allocation and power splitting for MISO-RSMA cognitive radio systems with SWIPT and information decoder users," in IEEE Systems Journal, 2020.

This paper studies rate-splitting in SWIPT with colocated information users and energy users. 

Nou-Orthogonal Unicast and Multicast (NOUM) Transmission

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting for multi-antenna non-orthogonal unicast and multicast transmission: Spectral and energy efficiency analysis," in IEEE Transactions on Communications, vol. 67, no. 12, pp. 8754-8770, Dec. 2019.

This is the first paper investigating RSMA in NOUM. A novel system model based on RSMA is proposed for NOUM which better reuses the SIC for the dual purpose of separating the unicast and multicast streams as well as better managing the multi-user.

• Y. Mao, and B. Clerckx, "Dirty paper coded rate-splitting for non-orthogonal unicast and multicast transmission with partial CSIT," arXiv preprint arXiv:2012.07542, 2020.

This paper investigates non-linear precoding of RSMA in NOUM. A novel dirty paper coded rate splitting (DPCRS) strategy is proposed, which achieves larger rate regions than DPC-assisted NOUM in MISO BC with partial CSIT.

Cooperative Transmission with User Relaying

• J. Zhang, B. Clerckx, J. Ge and Y. Mao, "Cooperative rate splitting for MISO broadcast channel with user relaying, and performance benefits over cooperative NOMA," in IEEE Signal Processing Letters, vol. 26, no. 11, pp. 1678-1682.

This is the first paper that proposes cooperative rate-splitting (CRS) with user-relaying in the two-user case. 

• Y. Mao, B. Clerckx, J. Zhang, V. O. K. Li and M. A. Arafah, "Max-min fairness of K-user cooperative rate-splitting in MISO broadcast channel with user relaying," in IEEE Transactions on Wireless Communications, vol. 19, no. 10, pp. 6362-6376, Oct. 2020.

This paper generalises the two-user CRS to the K-user case. 

• P. Li, M. Chen, Y. Mao, Z. Yang, B. Clerckx and M. Shikh-Bahaei, "Cooperative rate-splitting for secrecy sum-rate enhancement in multi-antenna broadcast channels," IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), London, United Kingdom, 2020.

This paper employs CRS technique to enhance the secrecy sum rate for the MISO BC with two legitimate users and one eavesdropper.

Cloud-Radio Access Network (C-RAN) 

• D. Yu, J. Kim and S. Park, "An efficient rate-splitting multiple access scheme for the downlink of C-RAN systems," in IEEE Wireless Communications Letters, vol. 8, no. 6, pp. 1555-1558, Dec. 2019.

This paper studies RSMA in C-RAN with fronthaul compression and fronthaul capacity constraint.

• A. A. Ahmad, J. Kakar, R. Reifert and A. Sezgin, "UAV-assisted C-RAN with rate splitting under base station breakdown scenarios," IEEE International Conference on Communications (ICC), Shanghai, China, 2019.

This paper studies a hybrid UAV-assisted C-RAN. Multiple UAVs act as the transmitters and cooperatively serve multiple users using RSMA.

• A. A. Ahmad et al., "Rate splitting and common message decoding for MIMO C-RAN systems," IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Cannes, France, 2019.

This paper studies rate-splitting in MIMO C-RAN when each user is equipped with multiple receive antennas.

• A. A. Ahmad, Y. Mao, A. Sezgin and B. Clerckx, "Rate splitting multiple access in C-RAN," IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications, London, United Kingdom, 2020.

This paper studies the performance of the generalized RS framework in C-RAN.

• A. A. Ahmad, H. Dahrouj, A. Chaaban, A. Sezgin, T. Y. Al-Naffouri and M. Alouini, "Power minimization via rate splitting in downlink cloud-radio access networks," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

The paper addresses the problem of minimizing the weighted transmit power subject to minimum QoS and fronthaul capacity constraints.

• A. A. Ahmad, B. Matthiesen, A. Sezgin and E. Jorswieck, "Energy efficiency in C-RAN using rate splitting and common message decoding," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This paper studies the energy efficiency (EE) maximization problem of rate-splitting in C-RAN. The global optimal EE solution is provided as a baseline to show the effectiveness of the proposed polynomial-time complexity algorithm.

• A. Alameer Ahmad, H. Dahrouj, A. Chaaban, A. Sezgin and M. Alouini, "Interference mitigation via rate-splitting and common message decoding in cloud radio access networks," in IEEE Access, vol. 7, pp. 80350-80365, 2019

This paper studies RSMA in C-RAN with data-sharing and fronthaul capacity constraint.

• A. Alameer Ahmad, Y. Mao, A. Sezgin, B. Clerckx, "Rate splitting multiple access in C-RAN: A scalable and robust design," arXiv preprint arXiv:2011.00076.

This paper studies RSMA in C-RAN with statistical CSIT (i.e., the transmitter only knows the distribution information of user channels).

• K. Weinberger, A. Alameer Ahmad, and A. Sezgin, "On synergistic benefits of rate splitting in IRS-assisted cloud radio access networks," arXiv preprint arXiv:2011.14763, 2020.

This paper utilizes the rate-splitting technique to mitigate interference (including the interference amplified by the intelligent reconfigurable surface) within the network. 

Coordinated Multi-Point (CoMP)

• Y. Mao, B. Clerckx and V. O. K. Li, "Rate-splitting multiple access for coordinated multi-point joint transmission," IEEE International Conference on Communications (ICC), Shanghai, China, 2019, pp. 1-6.

This is the first paper that studies RSMA in multi-cell networks. Specifically, it studies RSMA in downlink coordinated multi-point (CoMP) joint transmission (JT) networks and shows that RSMA outperforms SDMA and NOMA in a wide range of inter-user and inter-cell channel strength disparities.

Multigroup Multicast

• H. Joudeh and B. Clerckx, "Rate-splitting for max-min fair multigroup multicast beamforming in overloaded systems," in IEEE Transactions on Wireless Communications, vol. 16, no. 11, pp. 7276-7289, Nov. 2017.

This is the first paper of RSMA in multigroup multicast transmission. This work characterizes the max-min fairness (MMF) DoF achieved by RSMA in multigroup multicast with perfect CSIT. It also shows that RS exhibits strictly higher MMF-rates in partially and fully overloaded scenarios.

• O. Tervo, L. Trant, S. Chatzinotas, B. Ottersten and M. Juntti, "Multigroup multicast beamforming and antenna selection with rate-splitting in multicell systems," IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Kalamata, 2018.

This paper studies joint coordinated beamforming and antenna selection in multi-cell multi-user multigroup multicast MISO BC. Rate-splitting is shown to be achieve significant energy efficiency gain than conventional schemes. 

• H. Chen, D. Mi, Z. Chu, P. Xiao and R. Tafazolli, "Rate-splitting for multigroup multicast beamforming in multicarrier systems," IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Kalamata, 2018.

This paper studies the optimal MMF achieved by RSMA in multicarrier multigroup multicasting scenarios. 

• L. Yin and B. Clerckx, "Rate-splitting multiple access for multigroup multicast and multibeam satellite systems," in IEEE Transactions on Communications, 2020.

This paper characterizes the MMF DoF achieved by RSMA in multigroup multicast transmission with imperfect CSIT and demonstrates the benefits of RS strategies for both underloaded and overloaded scenarios.

• A. Z. Yalcin, M. Yuksel and B. Clerckx, "Rate splitting for multi-group multicasting with a common message," in IEEE Transactions on Vehicular Technology, vol. 69, no. 10, pp. 12281-12285, Oct. 2020.

This paper studies MMF-rate performance of RSMA for multigroup multicast transmission with a system-wide common message.

• H. Chen, D. Mi, B. Clerckx, Z. Chu, J. Shi and P. Xiao, "Joint power and subcarrier allocation optimization for multigroup multicast systems with rate splitting," in IEEE Transactions on Vehicular Technology, vol. 69, no. 2, pp. 2306-2310, Feb. 2020.

This paper studies joint precoder design and subcarrier allocation for multi-carrier multigroup multicast systems. Rate-splitting is shown to achieve explicit max-min fairness improvement than conventional schemes.

• H. Chen, D. Mi, Z. Liu, P. Xiao and R. Tafazolli, "Rate-splitting for overloaded multigroup multicast: Error performance evaluation," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This paper evaluates the error performance of the RS based transmission strategies with constellation-constrained coding/modulation.

Reconfigurable Intelligent Surface (RIS)

• H. Li, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part III: Interplay with Reconfigurable Intelligent Surfaces," in IEEE Communications Letters, 2022. 

This letter is the third part of a three-part tutorial that focuses on rate-splitting multiple access (RSMA) for 6G. As Part III of the tutorial, this letter provides an overview of integrating RSMA and reconfigurable intelligent surface (RIS). 

• Z. Yang, J. Shi, Z. Li, M. Chen, W. Xu and M. Shikh-Bahaei, "Energy efficient rate splitting multiple access (RSMA) with reconfigurable intelligent surface," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This is the first paper of RSMA for RIS, in which RSMA is shown to enhance the energy efficiency of RIS-assisted transmission networks.

• A. S. de Sena, P. H. J. Nardelli, D. B. da Costa, P. Popovski and C. B. Papadias, "Rate-Splitting Multiple Access and Its Interplay with Intelligent Reflecting Surfaces," in IEEE Communications Magazine, vol. 60, no. 7, pp. 52-57, July 2022, doi: 10.1109/MCOM.004.2100956. 

This article presents the potential of synergy between IRS and RSMA. Three important improvements achievable by IRS-RSMA schemes are identified, supported by insightful numerical examples, and mapped to beyond 5G use cases, along with future research directions. 

Physical Layer Security 

• P. Li, M. Chen, Y. Mao, Z. Yang, B. Clerckx and M. Shikh-Bahaei, "Cooperative rate-splitting for secrecy sum-rate enhancement in multi-antenna broadcast channels," IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), London, United Kingdom, 2020.

This paper employs CRS technique to enhance the secrecy sum rate of MISO BC with two legitimate users and one eavesdropper.

• H. Fu, S. Feng, W. Tang and D. W. K. Ng, "Robust secure beamforming design for two-user downlink MISO rate-splitting systems," in IEEE Transactions on Wireless Communications, vol. 19, no. 12, pp. 8351-8365, Dec. 2020.

This paper studies the max-min fairness for a downlink two-user MISO system with imperfect CSIT by taking into account a potential eavesdropper.

Non-linear Precoding

• A. R. Flores, B. Clerckx and R. C. de Lamare, "Tomlinson-harashima precoded rate-splitting for multiuser multiple-antenna systems," 15th International Symposium on Wireless Communication Systems (ISWCS), Lisbon, 2018.

This is the first paper that studies the non-linear precoding of RSMA in multi-antenna networks.

Satellite Communications

• M. Caus et al., "Exploratory analysis of superposition coding and rate splitting for multibeam satellite systems," 15th International Symposium on Wireless Communication Systems (ISWCS), Lisbon, 2018.

This paper shows the capability of rate-splitting to increase the spectral efficiency gains of multibeam satellite systems, while significantly reduces the feedback overhead. 

• L. Yin and B. Clerckx, "Rate-splitting multiple access for multibeam satellite communications," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This paper studies the beamforming design problem to achieve max-min fairness (MMF) in multibeam satellite communications.

• L. Yin and B. Clerckx, "Rate-splitting multiple access for multigroup multicast and multibeam satellite systems," in IEEE Transactions on Communications, 2020.

This paper studies the achievable rate of RSMA for multigroup multicast and multibeam satellite systems. It shows that RSMA is promising for multibeam satellite systems to manage inter-beam interference, taking into account practical challenges such as CSIT uncertainty, per-feed constraints, hot spots, uneven user distribution per beam, and overloaded regimes.

Joint Communication and Radar Transmission

• L. Yin, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part II: Interplay with Integrated Sensing and Communications," in IEEE Communications Letters, 2022.

This letter is the second part of a three-part tutorial focusing on rate-splitting multiple access (RSMA) for 6G. As Part II of the tutorial, this letter addresses the interplay between RSMA and integrated radar sensing and communications (ISAC). In particular, the introduces a general RSMA-assisted ISAC architecture, where the ISAC platform has a dual capability to simultaneously communicate with downlink users and probe detection signals to a moving target.  

• C. Xu, B. Clerckx, S. Chen, Y. Mao and J. Zhang, "Rate-splitting multiple access for multi-antenna joint communication and radar transmissions," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This is the first paper that applies RSMA in joint communication and radar transmission. The proposed RSMA-based joint communication and radar system is shown to achieve a better tradeoff between weighted sum rate and beam pattern approximation compared with the SDMA-based system.

Visible Light Communication (VLC)

• S. Tao, H. Yu, Q. Li, Y. Tang and D. Zhang, "One-layer rate-splitting multiple access with benefits over power-domain NOMA in indoor multi-cell visible light communication networks," IEEE International Conference on Communications (ICC), Dublin, Ireland, 2020.

This is the first paper that introduces RSMA to the multi-cell VLC networks. By taking into account the specific constraints of optical signals and the LED effect, 1-layer RSMA is shown to enhance the system spectral efficiency.

• S. Naser et al., "Rate-splitting multiple access: unifying NOMA and SDMA in MISO VLC channels," in IEEE Open Journal of Vehicular Technology, vol. 1, pp. 393-413, 2020.

This paper provides an overview of the key multiple access techniques used in VLC systems. It also discusses the capabilities and potentials of RSMA in VLC systems. 

Unmanned Aerial Vehicle (UAV)

• A. Rahmati, Y. Yapici, N. Rupasinghe, I. Guvenc, H. Dai and A. Bhuyan, "Energy efficiency of RSMA and NOMA in cellular-connected mmWave UAV networks," IEEE International Conference on Communications (ICC), Shanghai, China, 2019.

This paper investigates the energy efficiency of RSMA and NOMA in a millimeter-wave (mmWave) downlink UAV-assisted network. Numerical results indicates that RSMA is superior to NOMA in terms of overall energy efficiency.

• W. Jaafar, S. A. Naser, S. Muhaidat, P. C. Sofotasios and H. Yanikomeroglu, "On the downlink performance of RSMA-based UAV communications," in IEEE Transactions on Vehicular Technology, 2020.

This paper studies the joint optimization of UAV placement, RSMA precoding, and message split with the aim of maximizing the weighted sum rate.

• W. Jaafar, S. Naser, S. Muhaidat, P. C. Sofotasios and H. Yanikomeroglu, "Multiple access in aerial networks: From orthogonal and non-orthogonal to rate-splitting," in IEEE Open Journal of Vehicular Technology, vol. 1, pp. 372-392, 2020.

This paper gives a comprehensive survey of key multiple access techniques for aerial networks. It also studies RSMA in a two-user MISO BC with UAV serving as an aerial transmitter. 

Coded Caching

• E. Piovano, H. Joudeh and B. Clerckx, "On coded caching in the overloaded MISO broadcast channel," IEEE International Symposium on Information Theory (ISIT), Aachen, 2017.

This paper proposes a novel scheme to exploit the coded caching gain and leverage the available CSIT, which is shown to achieve a significant gain in terms of delivery time and CSIT quality requirement.

• E. Piovano, H. Joudeh and B. Clerckx, "Generalized degrees of freedom of the symmetric cache-aided MISO broadcast channel with partial CSIT," in IEEE Transactions on Information Theory, vol. 65, no. 9, pp. 5799-5815, Sept. 2019.

This paper generalizes and expands upon one-shot linear DoF results in the literature by including the parallel no-CSIT (or multicast) channel and by considering decentralization at the receivers.

Multicarrier Transmission

• L. Li, K. Chai, J. Li and X. Li, "Resource allocation for multicarrier rate-splitting multiple access system," in IEEE Access, vol. 8, pp. 174222-174232, 2020.

This paper proposes a joint power and muticarrier resource allocation scheme for multi-user multi-carrier RSMA. Random and zero-forcing beamforming are used for common and private messages.

• H. Chen, D. Mi, B. Clerckx, Z. Chu, J. Shi and P. Xiao, "Joint power and subcarrier allocation optimization for multigroup multicast systems with rate splitting," in IEEE Transactions on Vehicular Technology, vol. 69, no. 2, pp. 2306-2310, Feb. 2020.

This paper studies joint precoder design and subcarrier allocation for multi-carrier multigroup multicast systems. Rate-splitting is shown to achieve explicit max-min fairness improvement than conventional schemes.

Internet-of-Things 

• Y. Mao, E. Piovano, and B. Clerckx, "Rate-splitting multiple access for overloaded cellular internet of things," arXiv preprint arXiv:2008.01238, 2020.

This paper proposes a novel transmission framework based on RSMA for cellular IoT. The proposed scheme achieves the optimal DoF in the overloaded MISO BC with heterogeneous CSIT.

Waveform

• M. M. Şahin, O. Dizdar, B. Clerckx and H. Arslan, "OFDM-RSMA: Robust Transmission under Inter-Carrier Interference," in IEEE Transactions on Communications, 2024.

• Q. Huai, W. Yuan, Y. Wu and P. Fan, "Cross-Domain Transmission Scheme for Uplink OTFS-RSMA Based on Heterogeneous Mobile User Grouping," in IEEE Communications Letters, 2024.

• Clerckx, Bruno, et al. "Multiple Access Techniques for Intelligent and Multi-Functional 6G: Tutorial, Survey, and Outlook." arXiv preprint arXiv:2401.01433 (2024).

Multiple access (MA) is a crucial part of any wireless system and refers to techniques that make use of the resource dimensions to serve multiple users/devices/machines/services, ideally in the most efficient way. Given the needs of multi-functional wireless networks for integrated communications, sensing, localization, computing, coupled with the surge of machine learning / artificial intelligence (AI) in wireless networks, MA techniques are expected to experience a paradigm shift in 6G and beyond. In this paper, the authors provide a tutorial, survey and outlook of past, emerging and future MA techniques and pay a particular attention to how wireless network intelligence and multi-functionality will lead to a re-thinking of those techniques.

• A. Mishra, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part I: Principles, Applications and Future Works," in IEEE Communications Letters, 2022.

This letter is the first part of a three-part tutorial focusing on rate-splitting multiple access (RSMA) for 6G. As Part I of the tutorial, the letter presents the basics of RSMA and its applications in light of 6G. The letter delineates the design principle and basic transmission frameworks of downlink and uplink RSMA. The letter then illustrates the applications of RSMA for addressing the challenges of various potential enabling technologies and use cases, consequently making it a promising next generation multiple access (NGMA) scheme for future networks such as 6G and beyond.  

• L. Yin, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part II: Interplay with Integrated Sensing and Communications," in IEEE Communications Letters, 2022.

This letter is the second part of a three-part tutorial focusing on rate-splitting multiple access (RSMA) for 6G. As Part II of the tutorial, this letter addresses the interplay between RSMA and integrated radar sensing and communications (ISAC). In particular, the introduces a general RSMA-assisted ISAC architecture, where the ISAC platform has a dual capability to simultaneously communicate with downlink users and probe detection signals to a moving target.  

• H. Li, Y. Mao, O. Dizdar and B. Clerckx, "Rate-Splitting Multiple Access for 6G – Part III: Interplay with Reconfigurable Intelligent Surfaces," in IEEE Communications Letters, 2022. 

This letter is the third part of a three-part tutorial that focuses on rate-splitting multiple access (RSMA) for 6G. As Part III of the tutorial, this letter provides an overview of integrating RSMA and reconfigurable intelligent surface (RIS). 

• O. Dizdar, Y. Mao, W. Han and B. Clerckx, "Rate-Splitting Multiple Access: A New Frontier for the PHY Layer of 6G," 91st Vehicular Technology Conference (VTC)-Spring, 2020.

This paper discusses the emerging problems and core services of 5G, KPIs and characteristics of 6G, and how RSMA fits into these standards as an enabling technology.

• O. Dizdar, Y. Mao, Y. Xu, P. Zhu and B. Clerckx, "Rate-Splitting Multiple Access for Enhanced URLLC and eMBB in 6G: Invited Paper," 17th International Symposium on Wireless Communication Systems (ISWCS), 2021.

This paper studies the performance of RSMA in the scenarios related with the important core services of New Radio (NR) and 6G, namely, enhanced Ultra-Reliable and Low-Latency (URLLC) and enhanced Mobile Broadband Communications (eMBB).

• B. Clerckx et al., "A Primer on Rate-Splitting Multiple Access: Tutorial, Myths, and Frequently Asked Questions," in IEEE Journal on Selected Areas in Communications. 

In this tutorial, the authors depart from the orthogonal multiple access (OMA) versus non-orthogonal multiple access (NOMA) discussion held in 5G, and the conventional multi-user linear precoding approach used in space-division multiple access (SDMA), multi-user and massive MIMO in 4G and 5G, and show how multi-user communications and multiple access design for 6G and beyond should be intimately related to the fundamental problem of interference management. The authors start from foundational principles of interference management and rate-splitting, and progressively delineate RSMA frameworks for downlink, uplink, and multi-cell networks.  

• B. Clerckx et al., "Guest Editorial Rate Splitting for Future Wireless Networks," in IEEE Journal on Selected Areas in Communications. 

Rate splitting (RS) and rate splitting multiple access (RSMA) have emerged as a promising and powerful multiple access, interference management, and multi-user strategy for next-generation wireless systems and networks. This Special Issue is entirely dedicated to the theory, design, optimization, and applications of RS and RSMA in various network configurations. It starts with a guest editor-authored tutorial paper that delineates the basic principles and applications of RS and RSMA. The tutorial paper is then followed by 17 technical papers.   

• Xinze Lyu, Sundar Aditya, Bruno Clerckx, "Rate-Splitting Multiple Access for Overloaded Multi-group Multicast: A First Experimental Study," arXiv preprint:2406.15217 (2024).

• 3GPP. Rate Splitting Multiple Access (RSMA) for Multi-User MIMO - Enhancement of Unicast and Joint Unicast/Multicast Delivery. document RP-231938, 3GPP TSG RAN Meeting #101, BBC, Bangalore, India, Sept. 2023. (also as a contribution to 3GPP TSG RAN Rel-19 workshop, Taipei, Jun. 2023)

The first 3GPP contribution on RSMA.