Channel Charting for Pilot Reuse in mMTC with Spatially Correlated MIMO Channels

Massive multiple-input multiple-output (MIMO) systems and pilot reuse are essential ingredients for internet of things (IoT) networks and massive machine-type communications (mMTC). The large number of devices and the limited amount of resources (time, frequency, and power) preclude the allocation of orthogonal pilot sequences for users. We propose a pilot reuse strategy based on channel charting to deal with the pilot contamination in massive MIMO systems with spatially correlated channels. In particular, we use channel charting as a means to extract angular domain information from channel covariance matrices and assign orthogonal pilots to users with overlapping angle of arrival intervals. The simulation results show that the proposed pilot reuse method significantly improves the channel estimation performance and the symbol error rate as compared to existing schemes.