Published on in Vol 8, No 12 (2020): December
                                    Preprints (earlier versions) of this paper are
                                    available at
                                    https://preprints.jmir.org/preprint/22898, first published
                                    .
                                

1 Department of Electronics, Telecommunications and Informatics, Institute of Electronics and Informatics Engineering of Aveiro, University of Aveiro, Aveiro, Portugal
2 Department of Information and Communications Technologies, University of A Coruña, A Coruña, Spain
*these authors contributed equally
