Degrees of freedom for mutually interfering broadcast channels

Seok Hwan Park, Inkyu Lee

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


In this paper, we study spatial degree-of-freedom (DOF) for two mutually interfering broadcast channels (IBC). As the demand for space-division multiple access (SDMA) increases, the IBC where each link has a single transmit node and multiple receive nodes becomes important. This paper presents the results of the lower and upper bounds on the DOF of the IBC. From the derived results, it is shown that for most cases, zero-forcing (ZF) beamforming can achieve the optimal DOF of the IBC except for some special cases. Also, we identify a condition that disabling receive cooperation in the multiple-input multiple-output interference channels causes no DOF loss. It is confirmed that we cannot expect a DOF improvement by enabling in-cell receive cooperation if in at least one of two BSs, the number of antennas is greater than or equal to that of users per cell. Furthermore, we observe a positive result that as the number of users goes to infinity, the total DOF of the IBC converges to the interference-free DOF, which is the maximum achievable DOF in the absence of the inter-cell interference.

Original languageEnglish
Article number6121993
Pages (from-to)393-402
Number of pages10
JournalIEEE Transactions on Information Theory
Issue number1
Publication statusPublished - 2012 Jan

Bibliographical note

Funding Information:
Manuscript received October 20, 2008; revised July 19, 2011; accepted July 19, 2011. Date of current version January 06, 2012. This work was supported by the National Research Foundation of Korea (NRF) Grant 2010-0017909, funded by the Korea government (MEST). The material in this paper was presented in part at the 2009 IEEE International Conference on Communications. S.-H. Park was with the School of Electrical Engineering, Korea University, Seoul, Korea. He is now with the Agency for Defense Development, Daejeon, Korea (e-mail: I. Lee is with the School of Electrical Engineering, Korea University, Seoul, Korea (e-mail: Communicated by L. Zheng, Associate Editor for Communications. Digital Object Identifier 10.1109/TIT.2011.2170782 1In this paper, we refer to the multiplexing gain or capacity pre-log as degrees of freedom as in [5].


  • Beamforming
  • degrees of freedom
  • inter-cell interference
  • multi-user downlink
  • zero-forcing

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences


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