The feasibility conditions of interference alignment (IA) are analyzed for interfering broadcast-multiple-access channels in which one cell operates as downlink but the other cell operates as uplink. Under a general multiple-input and multiple-output antenna configuration, a necessary condition and a sufficient condition for one-shot linear IA are established, i.e., linear IA without symbol or time extension. In various example networks of interest, the optimal sum degrees of freedom (DoFs) are characterized by the derived necessary condition and sufficient condition. For symmetric DoF within each cell, a sufficient condition is established in a more compact expression, which yields the necessary and sufficient condition for a class of symmetric DoFs. An iterative construction of transmit and receive beamforming vectors is further proposed, which provides a specific beamforming design satisfying one-shot IA. Simulation results demonstrate that the proposed IA not only achieves larger DoF, but also significantly improves the sum rate over the single-cell operation in the practical signal-to-noise ratio regime.
Bibliographical noteFunding Information:
Manuscript received June 19, 2016; revised December 28, 2016; accepted April 16, 2017. Date of publication May 10, 2017; date of current version July 10, 2017. The work of S.-W. Jeon was supported by the Basic Science Research Program through the National Research Foundation of Korea, Ministry of Education, Science and Technology, under Grant NRF-2017R1A2B4012719. The work of K. Kim and D. K. Kim was supported by the IT Research and Development Program of MOTIE/KEIT (research on high speed and low power wireless communication SoC for high resolution video information mining) under Grant 10035389. The associate editor coordinating the review of this paper and approving it for publication was V. Cadambe. (Corresponding author: Dong Ku Kim.) S.-W. Jeon is with the Department of Military Information Engineering, Hanyang University, Ansan 15588, South Korea (e-mail: sangwoonjeon@ hanyang.ac.kr).
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All Science Journal Classification (ASJC) codes
- Computer Science Applications
- Electrical and Electronic Engineering
- Applied Mathematics