Speaker: Prof. Daniel Costa

Title: Rate-Splitting Multiple Access: Recent Advances from a Polarimetric Perspective 

Abstract: This talk will present three dual-polarized downlink transmission approaches for a massive MIMO-RSMA network under the effects of polarization interference and residual errors of imperfect SIC. It will be shown that the performance of all RSMA schemes is impressively higher than that of single and dual-polarized massive MIMO systems employing non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) techniques. Moreover, the potential synergy between intelligent reflecting surface (IRS) and RSMA will be discussed, in which it will be exploited the advanced capabilities of dual-polarized IRS for unleashing an enhanced RSMA polarization multiplexing. The talk will be concluded by discussing potential open problems and research challenges on the theme. 

Speaker: Prof. Theodoros Tsiftsis

Title: Cognitive Radio-Inspired Rate-Splitting Multiple Access Mobile Edge Computing  

Abstract: Cognitive radio (CR) techniques will be beneficial to future 6G wireless communications in developing spectrum agile multiple access and corresponding mobile edge computing (MEC) networks. In this talk, we present a rate-splitting multiple access (RSMA) scheme to aid an MEC system, where multiple randomly deployed users offload their computation tasks to an MEC server. Under the CR principles, we introduce the design of the rate-splitting parameters to attain the maximum achievable rate for the secondary user, meanwhile maintaining the primary user’s offloading performance the same as in orthogonal multiple access. Next, we reveal the impact of the user locations on the offloading performance of the proposed RSMA-MEC system, and various distance-based user pairing schemes are investigated by invoking stochastic geometry techniques. Finally, we will highlight the superior offloading performance achieved by the RSMA-MEC scheme, which attains a higher successful computation probability (SCP) than the existing schemes. 

Speaker: Prof. Zhaohui Yang

Title: The interplay between rate-splitting multiple access and emerging technologies 

Abstract: In downlink rate-splitting multiple access (RSMA), the base station divides the messages that can be transmitted to its users into a private part and a common part. Here, the common message is a message that multiple users want to receive, and the private message is a message that is dedicated to only a specific user. Due to the flexibility of controlling private and common messages, RSMA has the great potential in emerging technologies. In this talk, first, the basic properties of both uplink and downlink RSMA are provided with pointing out the potential use cases. Second, the advantage of RSMA in reconfigurable intelligence surface is provided. Third, the design of semantic communication over wireless networks with RSMA is presented. Fourth, the application scenarios of RSMA are summarized, including unmanned aerial vehicles (UAVs), integrated sensing and communication, digital twin, and fluid antenna system. Finally, the future directions and open problems about RSMA are provided. 

Speaker: Dr. Onur Dizdar

Title: Rate Splitting Multiple Access - Low-Complexity Designs for Practical Applications 

Abstract: Rate-Splitting Multiple Access (RSMA) is a flexible multiple access technique that can achieve enhanced and robust performance in multi-antenna wireless networks. As the studies on RSMA start to mature, its use in practical systems and future standards has come into light. This talk starts by giving background information and motives to employ RSMA in wireless networks. This will followed by details on RSMA-based system designs for underloaded and overloaded multi-antenna networks with low-complexity and near-optimal resource allocation methods. The talk will be concluded with discussions on opportunities and challenges on the way to the standardization of RSMA.

Speaker: Dr. David Vargas

Title: Rate-Splitting Multiple Access: Practical advancements for 5G, and the path to 6G 

Abstract: In this talk starting with industry requirements for IP media distribution over mobile broadband networks, I will discuss how RSMA as a physical layer radio interface architecture can help address important challenges such as connectivity in High Density Demand areas and scalability of popular live content. A significant amount of research literature on RSMA assumes Successive Interference Cancellation (SIC) receivers to decode the common and private streams. In our recent work we show how different designs - including SIC and non-SIC architectures - with different performance and complexity trade-offs can exploit the performance benefits of RSMA. The talk will also present our results on practical RSMA transceiver designs based on the 5G New Radio (NR) physical layer specifications that were submitted to the recent 3GPP Release-19 workshops to define features for the next phase of the 5G Advanced standard. We will focus on two use cases to enhance unicast MU-MIMO and Joint Unicast/Multicast MU-MIMO communications and compare the performance with standardised SDMA. Finally, the talk will present the timelines for the development of 6G as discussed at the ITU within the IMT-2030 framework.

Speaker: Prof. Jinhong Yuan

Title: A rate splitting scheme with efficient interference management: Discrete signalling and treating interference as noise 

Abstract: : It is known that rate splitting can achieve the largest rate region for many channel models. The key ingredients involved are superposition coding, successive interference cancellation, and Gaussian signalling. In this talk, we show that the superposition coding of practical discrete signalling and treating interference as noise (TIN) decoding can perform well close to the optimal rate region achieved by rate splitting. We first introduce a lattice-partition based multiple access scheme and show that the whole capacity region of the scalar Gaussian broadcast channel (BC) can be achieved to within a constant gap independent of channel parameters and user numbers. The successful generalizations of the proposed design to the BC channel with statistical CSI and to the interference channel are also presented.

Speaker: Prof. Vincent Wong

Title: Rate-Splitting for Intelligent Reflecting Surface-Aided Multiuser VR Streaming  

Abstract: : The growing demand for virtual reality (VR) applications requires wireless systems to provide a high transmission rate to support 360-degree video streaming to multiple users simultaneously. In this talk, we present an intelligent reflecting surface (IRS)-aided rate-splitting (RS) VR streaming system. In the proposed system, RS facilitates the exploitation of the shared interests of the users in VR streaming, and IRS creates additional propagation channels to support the transmission of high-resolution 360-degree videos. IRS also enhances the capability to mitigate the performance bottleneck caused by the requirement that all RS users have to be able to decode the common message. We formulate an optimization problem for maximization of the achievable bitrate of the 360-degree video subject to the quality-of-service constraints of the users. We propose a deep deterministic policy gradient with imitation learning algorithm, in which we leverage deep reinforcement learning and the hidden convexity of the formulated problem to optimize the IRS phase shifts, RS parameters, beamforming vectors, and bitrate selection of the 360-degree video tiles. Performance evaluation based on a real-world VR streaming dataset shows that the proposed IRS-aided RS VR streaming system outperforms several baseline schemes in terms of system sum-rate, achievable bitrate of the 360-degree videos, and online execution runtime. 

Speaker: Prof. Christos Masouros

Title: Rate Splitting Multiple Access: Security, Practicality and Emerging Applications   

Abstract:: In this talk, I aim to highlight challenges relating to Rate Splitting Multiple Access (RSMA). First, I will discuss unique security challenges arising in RSMA, where the existence of common messages that are visible to all users of the downlink opens up the opportunity for any user to act as an eavesdropper of other users’ data. This introduces a unique trade-off between security and the rate gains of RSMA. Formulating a power allocation scheme, my talk will address the question “how much of the split signal to reveal?”. Then I focus on the practicality of RSMA and its dependence on successive interference cancellation (SIC) at the receiver. Through the paradigm of non-orthogonal multiple access with user pairing, I aim to highlight the complexity issues of SIC and its dependence on imperfect channel state information at the receiver (CSIR), which is often overlooked. In this context, I will overview my teams recent work involving a constructive-interference approach that circumvents the need for SIC, as a first step in making NOMA and the more general RSMA practical. I will then discuss the application of RSMA on the emerging area of Integrated Sensing and Communications (ISAC) and reveal its benefits in improving the communication-vs-radar trade-off. I will conclude my talk with observations on RSMA and future research directions. 

Speaker: Prof. Yonghui Li

Title: Rate-Splitting Multiple Access for the Internet of Vehicles: Federated Edge  Learning and Platoon Control    

Abstract: RSMA has recently found favour in the multi-antenna aided wireless downlink, as a benefit of relaxing the accuracy of CSI at the transmitter (CSIT), while achieving high spectral efficiency, and providing security guarantees. These benefits are particularly important in high-velocity vehicular platoons, since their high Doppler affects the estimation accuracy of the CSIT. In this talk, I present a RSMA-based Internet of Vehicles (IoV) solution that jointly considers platoon control and federated edge learning (FEEL) in the downlink. The framework is designed for transmitting the unicast control messages within the IoV platoon, as well as for privacy-preserving FEEL aided downlink Non-Orthogonal Unicasting and Multicasting. A multi-objective optimization problem is formulated to minimize both the latency of the FEEL downlink and the deviation of the vehicles within the platoon. Simulation results show that the proposed RSMA-based IoV system outperforms both the Multi-User Linear Precoding and NOMA system and generate near-optimal solutions at a reduced complexity 

Speaker: Prof. Wonjae Shin

Title: Coordinated Rate-Splitting Multiple Access for Integrated Satellite-Terrestrial Networks with Super-Common Message    

Abstract: Rate-splitting multiple access (RSMA) is an emerging multiple access technique for multi-antenna networks that splits messages into common and private parts for flexible interference mitigation. Motivated by its robustness and scalability, it is promising to employ RSMA in integrated satellite-terrestrial networks (ISTN), where a satellite serves satellite users (SUs) broadly with a multibeam multicast transmission while terrestrial base station (BS) serves cellular users (CUs) with a unicast transmission, operating in the same frequency band. To avoid the data exchange between satellite/cellular networks via backhaul, we assume a coordinated ISTN relying on imperfect channel state information. We put forth a  coordinated RSMA  framework by applying inter-network rate-splitting (RS) with a super-common message on top of intra-network RS with common/private messages. With the unified RS design for inter- and intra-networks, we jointly optimize the precoding and power allocation of the private/common/super-common messages to achieve max-min fairness among all SUs and CUs through successive convex approximation. By doing so, the power of the super-common message can be adjusted according to interference levels of the satellite towards CUs, thereby potentially mitigating inter-network interference.

Speaker: Prof. Petar Popovski

Title: On the Protocol Aspects of Rate-Splitting Multiple Access 

Abstract: Interference management and multiple access represent a central aspect in the evolution of multi-user wireless systems. It spans a broad range of techniques, starting from the most traditional one of interference avoidance and orthogonalization and, at the other end, treatment of interference as a valid signal that is fully decodable. Rate-Splitting Multiple Access (RSMA) is a general framework for access and interference management that covers the described range of techniques and offers a number of parameters that can be optimized. This talk will start by providing a historical perspective on RSMA and its use in once-popular cognitive radio scenarios. This will be followed by discussion on spectral efficiency, energy efficiency and protocol/service aspects of RSMA, including user grouping and clustering. Finally, the talk will cover possible synergies of RSMA with the technology of Intelligent Reflective Surfaces (IRS). 

Speaker: Dr. Fan Wang

Title: Rate-Splitting for 6G Multi-User MIMO – Opportunities and Challenges 

Abstract: Network spectrum efficiency has been a key performance metric in wireless communication systems. Although 3GPP had discussed and specified different techniques, Space division multiple access (SDMA) was the major commercially successful technique in 4G assuming MIMO, and remained the same in 5G assuming mMIMO. Will SDMA continue to be the key technique in 6G mMIMO? In addition, uplink user experience has been emphasized in the ongoing 5.5G standard to better fit the modern traffic status. Is there any new implication on 6G MU-MIMO design concerning uplink? In this webinar talk, I will introduce some progress in 4G and 5G about the MU-MIMO techniques, and then share some thoughts on the opportunities and challenges of RSMA as a candidate 6G technique. 

Speaker: Prof. Eduard Jorswieck

Title: Rate Splitting and Resource Allocation in Interference Networks

Abstract: Rate splitting was introduced about forty years ago for the moderate interference channel. It was soon after applied to other multiuser channels including the multiple access channel. Until now, rate splitting and coded time sharing achieves the largest rate region for the interference channel. Furthermore, it is considered as a candidate technology for beyond 5G and 6G wireless networks. In the webinar talk, we briefly review the history of rate splitting in network information theory, formulate the resulting resource allocation and power control problems with and without rate splitting. The optimal rate splitting in interference channels is discussed based on market theory and a distributed algorithm explained. Finally, the challenges ahead to establish rate splitting as enabling technology in B5G and 6G networks are studied and corresponding research questions identified.

Speaker: Prof. Melda Yuksel

Title: Max-Min Fair Precoder Design and Power Allocation for Downlink MU-MIMO

Abstract: In this talk, a downlink multiple user (MU), multiple input multiple output (MIMO) wireless communication system is considered. In downlink MU-MIMO systems, the transmitter has unicast data for all users, and multiple users can form groups sharing the same resources. The objective is to design transmit precoders and power allocation coefficients jointly that provide max-min fairness (MMF) among the strongest users in each group, while maintaining minimum target rates for all the other users. The problem is solved via rate-splitting (RS) and two other iterative approaches. The first method is based on semi-definite relaxation (SDR) and successive convex approximation (SCA), and the second method is based on the minimum mean square error (MMSE) approach. For the latter approach, a simplification is also suggested to lower complexity. Proposed algorithms are also compared with orthogonal multiple access (OMA) and multi-user linear precoding (MULP) schemes in terms of both MMF rates and complexity. It is shown that while RS has the best MMF rates, the low-complexity MMSE approach has the least complexity. Moreover, the SDR/SCA approach offers an excellent tradeoff between the two.

Speaker: Prof. Aydin Sezgin

Title: Rate splitting: From fundamental principles to contemporary applications 

Abstract: The talk addresses the potential benefits of modern communication and cooperation techniques for 5G and beyond wireless networks. Important concepts discussed in the talk are rate-splitting and edge-caching and their interplay with interference alignment, (physical-layer) network coding, compute-and-forward relaying, and interference neutralization for enhanced interference and coexistence management. Different performance measures,  such as energy efficiency,  are considered and the performance of the novel concepts are compared to state of the art treating interference as noise approaches. The talk also addresses applications of the concepts in next generation wireless networks like Cloud-RAN and Fog-RAN.

Speaker: Prof. Pei Xiao

Title: Rate-splitting application and error performance analysis

Abstract: In this webinar talk, we first look at the application of rate-splitting (RS) to object-based broadcasting which allows the content of programmes to be customized according to the requirements and preferences of each individual viewer. It transforms the way how content is created and consumed and brings efficiencies and creative flexibility to content production teams, enabling them to deliver a personalised programme to audience. In the second part of the talk, we study radio source allocation schemes for the RS-based multigroup multicast system and formulate a joint optimization problem for precoder design and subcarrier allocation.  Finally, we evaluate the error performance of this RS-based system using a link level simulator in order to verify the practicality and viability of rate splitting for future wireless systems. The investigation reveals the superiority of the RS system over its non-RS counterparts in terms of error rate performance.

Speaker: Prof. Robert Schober

Title: Precoding and Decoding Schemes for Non-Orthogonal Downlink MIMO Systems 

Abstract: This talk will focus on downlink MIMO systems where both the base station and the users are equipped with multiple antennas. While it is well known that dirty paper coding (DPC) is capacity achieving in such systems, practical high-performance transmission schemes offering favorable trade-offs between performance and complexity are still under development, as most of the related literature has focused on single-antenna users. A key requirement for achieving such a favorable trade-off is the synergistic combination of linear precoding at the base station and successive interference cancellation (SIC) at the users. In this talk, we present two different approaches to downlink MIMO transmission. The first approach is based on MIMO-NOMA concepts and decomposes the MIMO channels of the users into scalar sub-channels with and without inter-user interference via suitable precoding and decoding matrices. The second approach is based on MIMO-RSMA and employs a successive null-space precoder to control the amount of inter-user interference experienced by the users. The performance of both schemes is compared to DPC and various orthogonal and non-orthogonal benchmark schemes. These comparisons reveal that the proposed MIMO-NOMA scheme achieves an excellent performance in overloaded MIMO systems, while the proposed MIMO-RSMA scheme performs well in underloaded MIMO systems and is robust to imperfect channel state information.

Speaker: Prof. Rodrigo C. de Lamare

Title: Precoding and Resource Allocation for Rate-Splitting-Based Multiple-Antenna Systems

Abstract: In this presentation, we will examine precoding and resource allocation techniques for the downlink of rate-splitting-based multiple-antenna systems. In particular, linear and nonlinear precoding strategies will be detailed along with stream combining strategies that are fundamental for the deployment of multiple antennas at user terminals and for improving the sum-rate performance of systems. We will also present power allocation approaches suitable for rate-splitting-based systems, which are based on exhaustive search strategies and efficient stochastic gradient-based learning algorithms. Results of rate-splitting-based multiple-antenna networks with co-located base stations and cell-free schemes will be presented and discussed along with future research directions.

Speaker: Prof. Carlos Mosquera

Title: Rate-Splitting and Space Communications, a Robust Alliance 

Abstract: This presentation covers  the application of rate-splitting techniques to address different practical limitations that are found in satellite settings, including multibeam communications or the secondary access to the spectrum of a broadcast operator. It will be shown how rate-splitting arises as the solution to deal with co-channel interference in several single-antenna and multi-antenna settings, under incomplete channel state information -lack of phase information-  and a need for link adaptation.

Speaker: Prof. Wolfgang Utschick

Title: Rate Splitting in FDD Massive MIMO Systems Based on the Second Central Moments of Transmission Channels and Incomplete Channel Knowledge

Abstract: In this talk, we present new results on the application of rate splitting (RS) in a multi-user scenario using massive multiple-input multiple-output (MaMIMO) transmitters at the base station (BS) of a frequency division duplex (FDD) system. In FDD systems, the lack of uplink (UL) and downlink (DL) channel state information (CSI) reciprocity typically requires feedback of the DL CSI from the receivers to the BS in the form of a compressed version of the CSI or alternatively by means of channel quality indicators and by signaling elements of a corresponding precoding codebook. The CSI available at the BS in our setup is gained from DL probing, where the training sequences are reused among the BS antennas, motivated by the scarcity of available pilot sequences in MaMIMO FDD systems. The users subsequently send through feedback their channel observation to the BS. Furthermore, we assume additional estimates of the second central moments of the unknown CSI at the BS. While partial CSI leads to severe degradation of standard multiuser precoding techniques, the recently proposed bilinear equalizer/precoder method for MaMIMO systems in combination with RS shows very promising results. In this talk, we, therefore, present the combination of these methods and demonstrate their superiority over other state-of-the-art methods using Monte Carlo simulations of typical communication scenarios. (Authors/Contributors: Donia Ben Amor, Michael Joham, Wolfgang Utschick)