Overdemodulation for High-Performance Receivers with Low-Resolution ADC

TL;DR

This paper investigates the limitations of classical quadrature demodulation in low-resolution ADC receivers and proposes overdemodulation to enhance channel parameter estimation and information transfer.

Contribution

It demonstrates that classical quadrature demodulation is suboptimal with low-resolution ADCs and analyzes how overdemodulation improves Fisher information and Shannon information in such systems.

Findings

Classical quadrature demodulation is suboptimal with 1-bit ADCs.

Overdemodulation increases Fisher information for channel estimation.

Overdemodulation enhances Shannon information under low-resolution quantization.

Abstract

The design of the analog demodulator for receivers with low-resolution analog-to-digital converters (ADC) is investigated. For infinite ADC resolution, demodulation to baseband with M = 2 orthogonal sinusoidal functions (quadrature demodulation) is an optimum design choice. For receive systems which are restricted to ADC with low amplitude resolution we show here that this classical demodulation approach is suboptimal. To this end we analyze the theoretical channel parameter estimation performance based on a simple pessimistic characterization of the Fisher information measure when forming M > 2 analog demodulation channels prior to an ADC with 1-bit amplitude resolution. In order to emphasize that this inside is also true for communication problems, we provide an additional discussion on the behavior of the Shannon information measure under overdemodulation and 1-bit quantization.