Analysis of Channel Hardening for SWIPT using Measured Massive MIMO Channels

The performance of simultaneous wireless information and power transfer (SWIPT) is often inhibited by high path-loss and multi-path fading. The massive multiple-input-multiple-output (MIMO) system is seen as an effective technique to overcome the wireless channel distortion. This work analyzes how massive MIMO enables channel hardening and thus influences the optimal SWIPT transmission strategy. This study focuses on the MISO case (i.e., 64-antenna transmitter and a single receiver node) and is done based on a non-linear energy harvesting model and measured channel state information (CSI). The results confirm that massive MIMO hardens the channel which makes frequency domain pre-equalization unnecessary for both non-line-of-sight (NLoS) and line-of-sight (LoS) channels. The impact is, as expected, more noticeable in NLoS scenario. We show that the array gain introduced by the 64-antenna transmitter using a 15-tone multi-sine signal, can improve the normalized power conversion efficiency (PCE) by more than 80%, and the channel capacity by more than 2 times, for both NLoS and LoS channels.