Start of Packet Detection and Synchronization for LoraWAN Modulated Signals

Abstract

LoRaWAN is one of the most employed systems among the Low PowerWide Area Networks. An open problem for the LoRaWAN system is the receiver’s overall synchronization, including the detection of the start of the LoRaWAN packet and the correction of the carrier frequency offset and time offset. The implementation of such a subsystem in currently available chipsets for LoRaWAN is not known. This paper provides a description of a new synchronization subsystem for a LoRaWAN receiver in realistic scenarios, considering the usual operating regions (in terms, for example, of Signal-to-Noise Ratio, maximum carrier frequency offset, and allowed Packet Error Rate). The ambiguity of the effects of the time offset and the carrier frequency offset on the LoRaWAN preamble are established analytically. Different options for the synchronization subsystem are provided, one of which is particularly suited if the requirements on the maximum frequency offset are those set for off–the–shelf chipsets. The performance of the proposed synchronization subsystem and the start of the packet detection algorithm is evaluated through a campaign of simulations. The results confirm that the proposed subsystem meets all of the requirements for successful demodulation and detection of the data part following the preamble.