Continuous phase modulation with 1-bit quantization and oversampling using iterative detection and decoding

Rodrigo R M De Alencar,Lukas T N Landau,Rodrigo C De Lamare

doi:10.1186/s13638-020-01856-5

Abstract

A channel with continuous phase modulation and 1-bit ADC with oversampling is considered. Due to oversampling, higher-order modulations yield a higher achievable rate and this study presents methods to approach this with sophisticated channel coding. Iterative detection and decoding is considered, which exploits the soft information extracted from oversampled CPM sequences. Besides the strategy based on conventional channel coding techniques, a tailored bit mapping is proposed where two bits can be detected reliably at high SNR and only the third bit is affected by the uncertainties from the coarse quantization. With this, a convolutional code is only applied to the third bit. Our experiments with a turbo receiver show that the iterative detection and decoding is a promising approach for exploiting the additional information brought by oversampling. Moreover, it is shown that the proposed method based on the tailored bit mapping corresponds to a lower bit error rate in comparison with the case of conventional channel coding.

Highlights

The energy consumption of an analog-to-digital converter (ADC) scales exponentially with its resolution in amplitude [1]
One promising approach to overcome the limitation with respect to the ADC power consumption is 1-bit quantization, i.e., only the sign of the signal is known to the receiver
By considering the capacity per unit cost, it has been shown in [2] that 1-bit quantization and oversampling at the receiver can de Alencar et al J Wireless Com Network (2020) 2020:237 be beneficial in a noisy scenario, as it was shown later in [7] for bandlimited channels

Summary

Introduction

The energy consumption of an analog-to-digital converter (ADC) scales exponentially with its resolution in amplitude [1]. We consider the design and analysis of CPM schemes with 1-bit quantization and oversampling at the receiver, employing channel coding in scenarios with higher modulation order. For such cases, based on the achievable rates computed in [17], channel coding is essential for establishing reliable communications In this context, this work extends the discrete system model for CPM signals received with 1-bit quantization and oversampling, presented in [17], for a sophisticated coding and decoding scheme. A higher sampling grid in the waveform signal, in the noise generation and in the filtering is adopted to adequately model the aliasing effect This receives filtering yields an increase in memory in the system by Lg symbols, where (Lg − 1)Ts < Tg ≤ Lg Ts. The filtered samples are decimated to the vector zkk−N according to the oversampling factor M, by multiplication with the D-fold decimation matrix D with dimensions.

Auxiliary channel law and channel output probability

A posteriori probabilities and soft information

Results and discussion

Conclusions