Nonlinear Inter-Band Subcarrier Intermodulations of Multi-RAT OFDM Wireless Services in 5G Heterogeneous Mobile Fronthaul Networks

Nonlinear impairments of OFDM signals in 5G multi-radio access technology (multi-RAT) heterogeneous mobile fronthaul (MFH) networks are investigated. Although nonlinear subcarrier intermodulations (IMs) of OFDM signals have been studied extensively, inter-band interferences among multiple OFDM services in multi-RAT heterogeneous systems have not been evaluated yet. In this paper, for the first time as we know, inter-band IMs among subcarriers of multiband OFDM services in a multi-RAT heterogeneous MFH network are investigated. A millimeter wave MFH testbed is used to evaluate the nonlinear interferences among multiple OFDM services from various radio access technologies (RATs). Both theoretical analysis and experiments are carried out, and it is verified that inter-band IMs among different OFDM services actually play a more important role in the MFH performance degradation than the well-known intra-band IMs of each individual service. Finally, nonlinearity compensation of MFH networks is demonstrated by predistortion technique, and effective mitigation of both intra- and inter-band subcarrier IMs are realized.