IEEE International Symposium on Personal, Indoor and Mobile Radio Communications
31 August-3 September 2020 // Virtual Conference

T04: Rate-Splitting Multiple Access for 6G


Dr Bruno Clerckx,
Dr Yijie Mao,
Imperial College London, UK


£50 Tutorial only | Tutorial + Full Conference access from £120

Half-day Tutorial, Monday 31st August 9:00 (BST)
Further pricing details can be found on the registration page.

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MIMO has grown beyond the original point-to-point channel and nowadays refers to a diverse range of centralized and distributed deployments. Numerous techniques have been developed in the last decade for MIMO wireless networks, including among others Multiuser-MIMO (MU-MIMO), CoMP, Massive MIMO, Non-Orthogonal Multiple Access (NOMA), millimetre wave (mmwave) MIMO. All those techniques rely on two extreme interference management strategies, namely fully decode interference and treat interference as noise. Indeed, while NOMA based on superposition coding with Successive Interference Cancellation (SIC) relies on strong users to fully decode and cancel interference created by weaker users, MU-MIMO/Massive MIMO/CoMP/mmwave MIMO based on linear precoding rely on fully treating any residual multi-user interference as noise. In the presence of imperfect channel state information at the transmitter (CSIT), CSIT inaccuracy results in additional multi-user interference that is treated as noise by all those techniques.

To efficiently cope with the high throughput, reliability, heterogeneity of Quality-of-Service (QoS), and massive connectivity requirements of future multi-antenna wireless networks, multiple access and multiuser communication system design need to depart from two conventional and extreme interference management strategies, namely fully treat interference as noise (as commonly used in 4G, MU-MIMO, CoMP, Massive MIMO, mmwave MIMO) and fully decode interference (as in NOMA).

In this tutorial, we depart from those two extremes and introduce the audience a more general, more robust, and more powerful transmission framework, called Rate-Splitting Multiple Access (RSMA) that relies on multi-antenna Rate-Splitting (RS) strategies at the transmitter and SIC receivers to decode part of the interference and treat the remaining part of the interference as noise. This capability of RS to partially decode interference and partially treat interference as noise enables to softly bridge and therefore reconcile the two extreme strategies of fully decode interference and treat interference as noise and provides room for QoS enhancements and complexity reduction. As a consequence, RS provides a more general and powerful class of non-orthogonal transmission, multiple access and interference management strategies.

In order to partially decode interference and partially treat interference as noise, RS splits messages into common messages decoded by multiple users, and private messages decoded by their corresponding users. As a result, RS pushes multiuser transmission away from conventional unicast-only transmission to superimposed non-orthogonal unicast and multicast transmission, and leads to a more general class/framework of strategies. For instance, in a MISO Broadcast Channel, RS is shown to flexible framework for non-orthogonal transmission that generalizes, and subsumes as special cases, four seemingly different strategies, namely Space Division Multiple Access (SDMA) based on linear precoding, Orthogonal Multiple Access (OMA), Non-Orthogonal Multiple Access (NOMA) based on linearly precoded superposition coding with SIC, and physical-layer multicasting. RS boils down to those strategies in some specific conditions, but outperforms them all in general. Through information and communication theoretic analysis, RS is shown to be optimal (from a Degrees-of-Freedom region perspective) in a number of scenarios and provides significant benefits in terms of spectral efficiency, reliability and CSI feedback overhead reduction over conventional strategies used in 5G that rely on fully treating interference as noise or fully decoding interference.

Structure and content

  1. Introduction to MIMO networks, interference management and 5G design
    • Point to point MIMO
    • Multi-user SISO/MIMO
    • Multi-cell MIMO and HetNets
    • Massive MIMO
    • Interference Management
    • Non-Orthogonal Multiple Access
  2. Problem of 4G and 5G architecture
    • LTE-A performance and limitations: NOMA, MU-MIMO, CoMP, HetNets
    • Motivation for a new physical layer
  3. Fundamentals of Rate-Splitting Multiple Access (40min)
    • Broadcast Channel with perfect and imperfect CSIT
    • RSMA transmitter and receiver architectures
    • Performance Limits and Degrees of Freedom
    • Sum-Rate Enhancement and CSI Feedback Reduction
    • Rate Analysis
  4. Transceiver Optimization of Rate-Splitting Multiple Access (20min)
    • Problem formulation
    • Robust beamforming (sum-rate maximization, max-min fairness)
  5. Applications and Extensions of Rate Splitting Multiple Access (85min)
    • RSMA with multiple receive antennas
    • RSMA for FDD Massive MIMO
    • RSMA for Multi-Cell MIMO
    • RSMA to generalize SDMA and NOMA
    • RSMA for Multigroup Multicast
    • RSMA for communications in the presence of RF impairments
    • RSMA for Millimeter Wave Communications
    • RSMA for mixed services: unicast and multicast transmissions
    • RSMA for Wireless Information and Power Transfer
    • RSMA for Satellite Communications
    • RSMA with user relaying
    • RSMA for joint communication and radar transmission,
    • RSMA to combat the curse of mobility in MIMO networks
    • RSMA for massive IoT connectivity
    • RSMA to mitigate pilot contamination in Massive MIMO
    • Entire PHY-layer design of RSMA
  6. Rate-Splitting Multiple Access for 6G
    • Standardization issues and efforts
  7. Future Challenges

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