Future wireless multiple-input multiple-output (MIMO) communication systems will employ sub-6 GHz and millimeter wave (mmWave) frequency bands working cooperatively. Establishing a MIMO communication link usually relies on estimating channel state information (CSI) which is difficult to acquire at mmWave frequencies due to a low signal-to-noise ratio (SNR). In this paper, we propose three novel methods to estimate mmWave MIMO channels using out-of-band information obtained from the sub-6GHz band. We compare the proposed channel estimation methods with a conventional one utilizing only in-band information. Simulation results show that the proposed methods outperform the conventional mmWave channel estimation method in terms of achievable spectral efficiency, especially at low SNR and high K-factor.

翻译：未来无线多输入多输出（MIMO）通信系统将协同使用sub-6 GHz和毫米波（mmWave）频段。建立MIMO通信链路通常依赖于信道状态信息（CSI）的估计，而由于信噪比（SNR）较低，在毫米波频段获取CSI较为困难。本文提出三种利用sub-6 GHz频段带外信息估计毫米波MIMO信道的新方法。我们将所提出的信道估计方法与仅利用带内信息的传统方法进行比较。仿真结果表明，所提出的方法在可实现频谱效率方面优于传统毫米波信道估计方法，尤其是在低信噪比和高K因子条件下。