Imperial College London
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ProfessorJulieMcCann

Faculty of Engineering, Department of Computing

Vice-Dean (Research) for the Faculty of Engineering
 
 
 
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Contact

 

+44 (0)20 7594 8375j.mccann Website

 
 
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Assistant

 

Miss Teresa Ng +44 (0)20 7594 8300

 
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Location

 

260ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Benkhelifa:2022:10.1109/JIOT.2022.3173060,
author = {Benkhelifa, F and Bouazizi, Y and McCann, J},
doi = {10.1109/JIOT.2022.3173060},
journal = {IEEE Internet of Things Journal},
pages = {19928--19944},
title = {How orthogonal is LoRa modulation?},
url = {http://dx.doi.org/10.1109/JIOT.2022.3173060},
volume = {9},
year = {2022}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - In this paper, we provide, for the first time, acomprehensive understanding of LoRa waveform theory in order to quantify its orthogonality. We present LoRa waveformexpressions in continuous and discrete time domains, and analyzemeasures of orthogonality between different LoRa spreadingfactors (SFs) through cross-correlation functions. The crosscorrelation functions are analytically expressed in a generalform and they account for diverse configuration parameters(bandwidth, SF, etc.) and different cases of signal displacements(time delay shift, frequency shift, etc.). We quantify their meanand maximum in all time domains. We highlight the impact ofthe temporal displacement and different bandwidths. The generalresult is that LoRa modulation is non-orthogonal. Firstly, weobserve that for same bandwidths the largest maximum crosscorrelation happens for same SF and is equal to 100% due to samesymbols; whereas for different bandwidths, the largest maximumcross-correlation is no longer observed at the same SF. Secondly,the maximum cross-correlation is less than 26% between differentSFs, is higher for closer SFs and decreases as the differencebetween SFs increases. After downchirping, the maximum crosscorrelation increases and the mean decreases compared to thosebefore downchirping. Moreover, the maximum cross-correlationis insignificantly impacted by the temporal delay which makes itvalid to adopt for the performance analysis of both synchronousand asynchronous systems. Finally, we analyze by simulation thebit error probability statistics for different bandwidth ratios andhighlight their correlated behaviour with the insights obtainedfrom the maximum cross-correlation expressions.
AU  - Benkhelifa,F
AU  - Bouazizi,Y
AU  - McCann,J
DO  - 10.1109/JIOT.2022.3173060
EP  - 19944
PY  - 2022///
SN  - 2327-4662
SP  - 19928
TI  - How orthogonal is LoRa modulation?
T2  - IEEE Internet of Things Journal
UR  - http://dx.doi.org/10.1109/JIOT.2022.3173060
UR  - http://hdl.handle.net/10044/1/96937
VL  - 9
ER  -
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