Mixed Time Scale Weighted Sum Rate Maximization for Hybrid Beamforming in Multi-Cell MU-MIMO Systems

C. Thomas, D. Slock
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引用次数: 12

Abstract

This work deals with hybrid beamforming for the MIMO Interfering Broadcast Channel (IBC), i.e. the Multi-Input Multi-Output (MIMO) Multi-User Multi- Cell downlink. In the case of massive MIMO with a large number of antennas at the base station, it may not be feasible to have as many RF chains ℳ as the number of antennas $N_t$. Hybrid beamforming (BF) involves two stage precoders with an analog stage in RF and a digital stage in baseband. Key assumptions here are that the fully connected analog stage consists of phase shifters and cannot be adapted at the fast fading rate. We consider BF design by maximizing the Weighted Sum Rate (WSR) for the case of Perfect Channel State Information at the Transmitter (CSIT). However, whereas analog and digital beamformers are optimized jointly only from time to time, only the digital beamformers are updated at the fast fading rate with the analog beamformer stage being frozen over the slow fading coherence times. Simulation results show that even if the analog beamformer gets outdated, close to optimal performance gets obtained thanks to the self averaging of large antenna systems. The simulations also show significant improvements compared to suboptimal covariance CSIT based designs for the analog BF.
多小区MU-MIMO系统混合波束形成的混合时间尺度加权和速率最大化
这项工作涉及MIMO干扰广播信道(IBC)的混合波束形成,即多输入多输出(MIMO)多用户多小区下行链路。在基站大量天线的大规模MIMO情况下,拥有与天线数量$N_t$一样多的RF链可能不可行。混合波束形成(BF)包括两级预编码器,在RF中为模拟级,在基带中为数字级。这里的关键假设是,完全连接的模拟级由移相器组成,不能适应快速衰落速率。在发送端信道状态信息完备的情况下,我们通过最大化加权和率来考虑BF的设计。然而,尽管模拟波束形成器和数字波束形成器只是不时地联合优化,但只有数字波束形成器以快速衰落速率更新,而模拟波束形成器阶段在缓慢衰落相干时间内被冻结。仿真结果表明,即使模拟波束形成器过时,由于大型天线系统的自平均,也能获得接近最优的性能。与基于次优协方差CSIT的模拟BF设计相比,仿真也显示出显著的改进。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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