Out-of-band radiation and cfo immunity of potential 5G multicarrier modulation schemes

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2015




In this study, generalized frequency division multiplexing (GFDM) and windowed cyclic prefix circular offset quadrature amplitude modulation (WCP-COQAM), which are candidate physical layer modulation schemes for the 5G systems, are compared to orthogonal frequency division multiplexing (OFDM) in terms of out-of-band (OOB) radiation levels and carrier frequency offset (CFO) immunity. GFDM and WCP- COQAM are shown to be superior to OFDM with respect to OOB emissions in some studies in literature. However, we consider that these comparisons are made under unfair conditions since OOB reduction techniques are not also applied to OFDM and the spectral efficiencies of the three modulations are not equal. Establishing fair comparison grounds accordingly, the simulation results yielded no significant OOB emission performance difference between the three modulation types. Further simulations considering some parameters related to the transmitted signals such as error-vector magnitude or average power under the effects of amplifier nonlinearity or digital-to- analog converter also revealed no significant difference between the three modulation types under LTE spectral mask requirements. The three modulation types are also compared in terms of their carrier frequency offset (CFO) immunities. To achieve better CFO immunity, advanced pulse shaping methods defined for offset quadrature amplitude modulation OFDM (OQAM- OFDM) are also applied to WCP-COQAM. This is possible since the two modulations are also proved to be equivalent in terms of orthogonality, which is one of the main analytic contributions of this thesis. However, the error rate performance simulations under CFO for various channel conditions did not improve CFO immunity for WCP-COQAM or GFDM compared to OFDM.