This work was funded by Instituto de Telecomunicac¸~oes (IT) under project HelicalMETA—UIDB/50008/2020. T. A. Morgado acknowledges FCT for research financial support with reference CEECIND/04530/2017 under the CEEC Individual 2017 and ITCoimbra for the contract as an assistant researcher with Reference CT/No. 004/2019-F00069. G. L. Jo~ao acknowledges support by ITCoimbra under a scientific initiation grant within the scope of the project HelicalMETA—UIDB/50008/2020. R. A. M. Pereira acknowledges support by FCT, POCH, and the co-financing of Fundo Social Europeu under the fellowship SFRH/BD/145024/ 2019. D. E. Fernandes acknowledges support by FCT, POCH, and the co-financing of Fundo Social Europeu under the fellowship SFRH/BPD/116525/2016 and by IT-Lisbon under the research contract with reference C-0042-2. S. Lannebe`re acknowledges financial support by IT-Coimbra under the research contract with Reference DL 57/2016/CP1353/CT0001.