Degrees of Freedom Regions of Two-User MIMO Z and Full Interference Channels: The Benefit of Reconfigurable Antennas

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Ke, Lei
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Wang, Zhengdao
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Electrical and Computer Engineering

The Department of Electrical and Computer Engineering (ECpE) contains two focuses. The focus on Electrical Engineering teaches students in the fields of control systems, electromagnetics and non-destructive evaluation, microelectronics, electric power & energy systems, and the like. The Computer Engineering focus teaches in the fields of software systems, embedded systems, networking, information security, computer architecture, etc.

The Department of Electrical Engineering was formed in 1909 from the division of the Department of Physics and Electrical Engineering. In 1985 its name changed to Department of Electrical Engineering and Computer Engineering. In 1995 it became the Department of Electrical and Computer Engineering.

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  • Department of Electrical Engineering (1909-1985)
  • Department of Electrical Engineering and Computer Engineering (1985-1995)

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We study the degrees of freedom (DoF) regions of two-user multiple-input multiple-output Z and full interference channels in this paper. We assume that the receivers always have perfect channel state information. We first derive the DoF region of Z interference channel with channel state information at transmitter (CSIT). For full interference channel without CSIT, the DoF region has been fully characterized recently and it is shown that the previously known outer bound is not achievable. In this paper, we investigate the no-CSIT case further by assuming that one transmitter has the ability of antenna mode switching. We obtain the DoF region as a function of the number of available antenna modes and reveal the incremental gain in DoF that each additional antenna mode can bring. It is shown that, in certain cases, the reconfigurable antennas can increase the DoF. In these cases, the DoF region is maximized when the number of modes is at least equal to the number of receive antennas at the corresponding receiver, in which case the previous outer bound is achieved. In all cases, we propose systematic constructions of the beamforming and nulling matrices for achieving the DoF region. The constructions bear an interesting space-frequency coding interpretation.


This is a manuscript of an article published as Ke, Lei, and Zhengdao Wang. "Degrees of freedom regions of two-user MIMO Z and full interference channels: The benefit of reconfigurable antennas." IEEE Transactions on Information Theory 58, no. 6 (2012): 3766-3779. DOI: 10.1109/TIT.2012.2185483. Posted with permission.

Sun Jan 01 00:00:00 UTC 2012