李士超， 邱玲^*

（  中国科学技术大学电子工程与信息科学系，合肥 230027；  ）

摘要： 本文针对基于训练的多用户多输入多输出（MU-MIMO）系统研究能量效率优化方法，形成了能效优化的功率分配问题。针对发送端信道状态信息不可见的事实提出一种两步优化方法，分别优化各态历经能量效率和瞬时能量效率。在各态历经能量效率的优化中，本文根据已推导的各态历经可达速率的更紧致下界将原问题转化为关于各态历经能量效率下界的优化问题，并证明了它关于训练功率和数据功率是联合拟凹的，进一步提出了一种交替优化求解算法。在瞬时能量效率的优化中，发送端采用基于各态历经能量效率优化得到的训练序列功率发送训练序列，接收端进行信道估计得到有误差的信道状态信息，并据此预测瞬时能量效率，进一步提出了一种用于优化数据信号发送功率的瞬时能量效率优化算法。仿真结果表明，本文所提出的两步能量效率优化算法相比于只优化各态历经能量效率的算法和频效优化的算法均能提高能量效率。
关键词： 通信与信息系统；多用户MIMO系统；优化；能量效率

Li Shichao， QIU Ling^*

（  Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei 230027；  ）

Abstract： This paper studies energy efficiency (EE) optimization in training-based multiuser multiple-input multiple-output (MU-MIMO) systems and formulates an energy-efficient power optimization problem. Considering the channel state information at transmitter (CSIT) unavailable fact, this paper proposes a two-step optimization scheme which consists of the ergodic EE and instant EE optimization. In the ergodic EE optimization, this paper transforms the original problem into the optimization of the ergodic EE's lower bound based on a derived tighter lower bound of the achievable rate. It is proved that this problem is jointly quasi-concave with respect to training power and data power, and then an alternating optimization algorithm is further proposed to solve it. In the instant EE optimization, the transmitter transmits the training with the power obtained in the ergodic EE optimization, which is used for channel estimation and result in imperfect CSI. This paper predicts the instant EE according to this imperfect CSIT and further proposes an instant EE optimiztion algorithm to optimize the data power. Simulation results show that our proposed two-step EE optimization algorithm can improve EE in MU-MIMO systems compared to the spectral-efficient scheme and the one-step scheme only with the ergodic EE optimization.

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