On angular-domain channel estimation for one-bit massive MIMO systems with fixed and time-varying thresholds

This paper considers angular-domain channel estimation for massive MIMO systems with one-bit analog-to-digital converters (ADCs) at base stations. We characterize analytical performance, in terms of the Cramer-Rao bound (CRB), on estimating the two-dimensional channel matrix (including angle-of-departure, angle-of-arrival and associated channel path gains) in the angular-domain representation. Our analysis provides a simple tool to compare channel estimation performance among several one-bit quantization schemes. We demonstrate that, with a fixed zero-threshold and when the noise variance is unknown, the Fisher information matrix becomes singular due to an ambiguity between the channel path gain and noise variance. This ambiguity can be removed if one-bit ADCs use a non-zero or a time-varying threshold quantization scheme. Numerical results are provided for performance verification as a function of SNR and the number of pilots.