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Identifier

000419287

Title

Exploring LoRaWAN PHY & MAC layers performance limits

Alternative Title

Εξερευνώντας τα όρια απόδοσης των επιπέδων PHY και MAC του LoRaWAN

Author

Γκιόλιας, Αθανάσιος Γ.

Thesis advisor

Δημητρόπουλος, Ξενοφώντας

Reviewer

Τσακαλίδης, Παναγιώτης
Παπαδοπούλη, Μαρία

Abstract

The demand for connected devices, according to the Internet of Things (IoT) paradigm, is expected to grow considerably in the immediate future. Various standards are currently contending to surpass the competition and provide the massive connectivity that will be required by a world in which everyday objects are expected to communicate with each other. The Low Power Wide Area Networks (LPWANs) appear as a solution to these demands. LPWANS provide improved range and less power consumption, at the expense of lower data rates, making them ideal candidates for IoT devices. In this thesis we examine a recently introduced PHY layer called LoRa (Long-Range) and the accompanying MAC layer protocol LoRaWAN. The aim of our work is to study several aspects of the LoRaWAN PHY and MAC layers, through extensive simulations and real-world experiments in order to reach to fruitful conclusions regarding the LoRaWAN performance. A simplified LoRa transceiver was implemented on Software Defined Radio (SDR) in order to study and analyze the time and frequency synchronization procedure of real devices in detail. The mathematical background of the synchronization and demodulation process of Lora was explored, while a potential algorithm that may be used by LoRaWAN gateways to correct transmission errors with high coding rate was also developed. Moreover, a pair of low-cost LoRa/LoRaWAN capable devices was assembled that allowed us to perform real-world experiments regarding the transmission range, power consumption and compare the behariour of several data rates. The open-source library and applications that were created and used during this work, facilitate the configuration of the devices and the collection of uplink/downlink data to create coverage maps. Furthermore, a complete LoRaWAN simulator was created and an extensive set of simulation results is presented and examined accordingly. Our simulator has a large number of tunable parameters and uses three distinct path loss models in order to be able to fine tune the simulations and reach to more solid conclusions. Therefore, it can assist in the understanding of the effects that several choices can have during a LoRaWAN network design, such as network density, choice of data rates, percentages of nodes with confirmed uplinks, transmission power and even the positioning of the nodes and gateways in the real world. Through this work, we verified a synchronization method for LoRa while also revealed important details regarding a way to correct LoRa uplink transmission errors with low overhead, keeping the existing packet structure. Moreover, our simulator compared with similar works, provides more reliable results which are closer to real-world network deployments, taking also the battery life into account.

Language

English

Subject

Error coding

IoT

LoRa

Model

Sensor network

Simulator

Synchronization

WSN

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