Rate-splitting for max-min fair multigroup multicast beamforming in overloaded systems

Hamdi Joudeh, Bruno Clerckx

Research output: Contribution to journalArticleAcademicpeer-review

125 Citations (Scopus)


In this paper, we consider the problem of achieving max-min fairness amongst multiple co-channel multicast groups through transmit beamforming. We explicitly focus on overloaded scenarios in which the number of transmitting antennas is insufficient to neutralize all inter-group interference. Such scenarios are becoming increasingly relevant in the light of growing low-latency content delivery demands, and also commonly appear in multibeam satellite systems. We derive performance limits of classical beamforming strategies using degrees of freedom (DoF) analysis unveiling their limitations; for example, rates saturate in overloaded scenarios due to inter-group interference. To tackle interference, we propose a strategy based on degraded beamforming and successive interference cancellation. While the degraded strategy resolves the rate-saturation issue, this comes at a price of sacrificing all spatial multiplexing gains. This motivates the development of a unifying strategy that combines the benefits of the two previous strategies. We propose a beamforming strategy based on rate-splitting (RS), which divides the messages intended to each group into a degraded part and a designated part, and transmits a superposition of both degraded and designated beamformed streams. The superiority of the proposed strategy is demonstrated through DoF analysis. Finally, we solve the RS beamforming design problem and demonstrate significant performance gains through simulations.

Original languageEnglish
Article number8019852
Pages (from-to)7276-7289
Number of pages14
JournalIEEE Transactions on Wireless Communications
Issue number11
Publication statusPublished - Nov 2017
Externally publishedYes


  • Downlink beamforming
  • Overloaded transmission
  • Physical layer multicasting
  • Rate-splitting
  • WMMSE approach


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