OFDM over mm-Wave OAM Channels in a Multipath Environment with Intersymbol Interference

This paper reports an experimental investigation of using orthogonal frequency division multiplexing (OFDM) on orbital-angular momentum (OAM) channels when there is intersymbol interference (ISI) caused by multipath effects. The impulse response measurement indicates that due to the divergence of OAM beams, channels of larger OAM number are more affected by the ISI caused the reflections from surrounding objects. Channel performance of three different OAM numbers l = 0, +1 and +3 are studied. When a single QPSK channel is used, the more channel performance degradation in term of BER and EVM is observed for higher OAM channels. OFDM with 4 sub-carriers is used on the OAM channels to help reduce the ISI and improve the channel performance to some extent.