Blind phase/frequency synchronization with low-precision ADC: A Bayesian approach

Modern communication receivers heavily leverage Moore's law, which enables low-cost implementations of sophisticated functionalities in digital signal processing (DSP). However, as communication systems scale up in bandwidth, the availability of analog-to-digital converters (ADCs) becomes a fundamental bottleneck for such DSP-centric design. In this paper, we investigate a canonical problem of blind carrier phase and frequency synchronization in order to obtain insight into the performance limitations imposed by severe quantization constraints. We consider an ideal Nyquist sampled QPSK system with coarse phase quantization, implementable with one bit ADCs after analog linear combinations of in-phase (I) and quadrature (Q) components. We propose blind Bayesian algorithms for rapid phase acquisition, followed by continuous feedback-based phase/frequency tracking, based on jointly modeling the unknown phase and frequency, the unknown data, and the severe nonlinearity introduced due to coarse phase quantization. Our performance evaluation shows that excellent performance, close to that of an unquantized system, is achieved by the use of 12 phase bins (implementable using 6 one-bit ADCs).