Journal of the Institute of Electronics and Information Engineers (전자공학회논문지)

The Institute of Electronics and Information Engineers (대한전자공학회)
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Optimization Algorithm for Energy-Efficiency in the Multi-user Massive MIMO Downlink System with MRT Precoding

MRT 기법 사용 시 다중 사용자 다중 안테나 하향링크 시스템에서의 에너지 효율 향상을 위한 최적화 알고리즘

  • Lee, Jeongsu (Department of Electrical and Electronic Engineering, Yonsei University) ;
  • Han, Yonggue (Department of Electrical and Electronic Engineering, Yonsei University) ;
  • Sim, Dongkyu (Department of Electrical and Electronic Engineering, Yonsei University) ;
  • Lee, Chungyong (Department of Electrical and Electronic Engineering, Yonsei University)
  • 이정수 (연세대학교 전기전자공학과) ;
  • 한용규 (연세대학교 전기전자공학과) ;
  • 심동규 (연세대학교 전기전자공학과) ;
  • 이충용 (연세대학교 전기전자공학과)
  • Received : 2015.02.17
  • Accepted : 2015.07.26
  • Published : 2015.08.25
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Abstract

Under the maximum transmit power constraint and the minimum rate constraint, we propose the optimal number of transmit antennas and transmit power which maximize energy-efficiency (EE) in multi-user multiple-input multiple-output (MIMO) downlink system with the maximal ratio transmission (MRT) precoding. Because the optimization problem for the instantaneous channel is difficult to solve, we use independence of individual channel, average channel gain and path loss to approximate the objective function. Since the approximated EE optimization problem is two-dimensional search problem, we find the optimal number of transmit antennas and transmit power using Lagrange multipliers and our proposed algorithm. Simulation results show that the number of transmit antennas and power obtained by proposed algorithm are almost identical to the value by the exhaustive search.

본 논문에서는 사용 가능한 최대 송신 전력과 만족해야 하는 최소 전송률에 대한 제한 조건 아래에서, maximal ratio transmission (MRT) 기법 사용 시 다중 사용자 다중 안테나 하향링크 시스템의 에너지 효율을 최대화하는 최적의 안테나 수와 송신 전력을 찾는 알고리즘을 제시한다. 순시 채널에 대한 최적화 문제는 직접 풀기 어려우므로 단말 간 채널의 독립성, 평균 채널 이득, 평균 path loss를 이용하여 근사한다. 근사된 에너지 효율에 대한 최적화 문제는 두 개의 변수를 동시에 고려해야 하는 2차원 최적화 문제가 된다. 우리는 이러한 2차원 최적화 문제를 라그랑지 승수법과 제안하는 알고리즘을 통하여 최적의 안테나 수와 송신 전력을 구한다. 실험을 통해, 제안하는 알고리즘으로 구한 최적의 송신 안테나 수와 송신 전력이 exhaustive search로 찾은 값과 근사함을 확인한다.

Keywords

References

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