Coordinated beamforming with relaxed zero forcing: The sequential orthogonal projection combining method and rate control

Juho Park, Gilwon Lee, Youngchul Sung, Masahiro Yukawa

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


In this paper, coordinated beamforming based on relaxed zero forcing (RZF) for K transmitter-receiver pair multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) interference channels is considered. In the RZF coordinated beamforming, conventional zero-forcing interference leakage constraints are relaxed so that some predetermined interference leakage to undesired receivers is allowed in order to increase the beam design space for larger rates than those of the zero-forcing (ZF) scheme or to make beam design feasible when ZF is impossible. In the MISO case, it is shown that the rate-maximizing beam vector under the RZF framework for a given set of interference leakage levels can be obtained by sequential orthogonal projection combining (SOPC). Based on this, exact and approximate closed-form solutions are provided in two-user and three-user cases, respectively, and an efficient beam design algorithm for RZF coordinated beamforming is provided in general cases. Furthermore, the rate control problem under the RZF framework is considered. A centralized approach and a distributed heuristic approach are proposed to control the position of the designed rate-tuple in the achievable rate region. Finally, the RZF framework is extended to MIMO interference channels by deriving a new lower bound on the rate of each user.

Original languageEnglish
Article number6502742
Pages (from-to)3100-3112
Number of pages13
JournalIEEE Transactions on Signal Processing
Issue number12
Publication statusPublished - 2013


  • Coordinated beamforming
  • Pareto-optimal
  • inter-cell interference
  • multi-cell MIMO
  • rate control
  • relaxed zero-forcing
  • sequential orthogonal projection combining

ASJC Scopus subject areas

  • Signal Processing
  • Electrical and Electronic Engineering


Dive into the research topics of 'Coordinated beamforming with relaxed zero forcing: The sequential orthogonal projection combining method and rate control'. Together they form a unique fingerprint.

Cite this