Line-of-Sight Massive MIMO Channel Characteristics in an Indoor Scenario at 94 GHz

The fading and correlation characteristics of virtual, yet realistic, line-of-sight (LOS) 4 × 2500 millimetric (mmW) massive MIMO channels are investigated at 94 GHz in an indoor office environment for three different Tx-Rx distance scenarios. The capability of the mmW massive MIMO channel to spatially decorrelate the users is evaluated with the computation of the channel correlation and other channel metrics, such as power-to-interference ratio and condition number. In particular, the correlation between channel vectors for a given user and its influence on receiving correlation is discussed. The results clearly demonstrate the capability of mmW massive MIMO systems to reach orthogonal Tx-Rx streams even for a small 7 × 7 antenna array subset with correlation between users <;0.2. Moreover, strong phase variations at Tx side at this frequency range are highlighted through channel phase correlation studies and were shown to contribute to the decorrelation at Rx side between close users, paving the way for further massive MIMO system enhancements.