EC-GSM-IoT Network Synchronization with Support for Large Frequency Offsets

TL;DR

This paper introduces a low-complexity synchronization algorithm for EC-GSM-IoT that effectively handles large frequency offsets and operates reliably at very low SNR levels, supporting cost-effective hardware.

Contribution

A novel synchronization algorithm supporting up to 50 kHz frequency offset, surpassing 3GPP requirements, enabling robust network synchronization at extremely low SNRs in EC-GSM-IoT.

Findings

Supports initial frequency offsets up to 50 kHz.

Operates reliably at SNR as low as -11.5 dB.

Enables low-cost oscillator use in EC-GSM-IoT devices.

Abstract

EDGE-based EC-GSM-IoT is a promising candidate for the billion-device cellular IoT (cIoT), providing similar coverage and battery life as NB-IoT. The goal of 20 dB coverage extension compared to EDGE poses significant challenges for the initial network synchronization, which has to be performed well below the thermal noise floor, down to an SNR of -8.5 dB. We present a low-complexity synchronization algorithm supporting up to 50 kHz initial frequency offset, thus enabling the use of a low-cost +/-25 ppm oscillator. The proposed algorithm does not only fulfill the 3GPP requirements, but surpasses them by 3 dB, enabling communication with an SNR of -11.5 dB or a maximum coupling loss of up to 170.5 dB.