  Employing low-resolution analog-to-digital converters (ADCs) for millimeter
wave receivers with large antenna arrays provides opportunity to efficiently
reduce power consumption of the receiver. Reducing ADC resolution, however,
results in performance degradation due to non-negligible quantization error. In
addition, the large number of radio frequency (RF) chains is still not
desirable. Accordingly, conventional low-resolution ADC systems require more
efficient designs to minimize the cost and complexity while maximizing
performance. In this article, we discuss advanced low-resolution ADC receiver
architectures that further improve the spectral and energy efficiency tradeoff.
To reduce both the numbers of RF chains and ADC bits, hybrid analog-and-digital
beamforming is jointly considered with low-resolution ADCs. We explore the
challenges in designing such receivers and present key insights on how the
advanced architectures overcome such challenges. As an alternative
low-resolution ADC receiver, we also introduce receivers with learning-based
detection. The receiver does not require explicit channel estimation, thereby
is suitable for one-bit ADC systems. Finally, future challenges and research
issues are discussed.
