Iterative Semi-Coherent Receiver for Coded LoRa Systems

Abstract

This letter presents a novel design of an iterative receiver for low-power long-range (LoRa) systems with channel coding and semi-coherent receiver. To enable soft-input-soft-output (SISO) decoding, closed-form expressions for the exact distribution of the received signal samples and the resulting log-likelihood ratios of the coded bits are obtained. Next, we propose an iterative semi-coherent receiver that performs iterative processing among the soft-output demodulator, the SISO channel decoder, and the blind channel estimator, i.e., without any training overhead. Simulation results show that our proposed receiver outperforms non-coherent receiver, and closely approaches the ideal coherent receiver’s performance.