Multi-band microwave vector signal generation and transmission for mobile fronthaul networks

A multi-band microwave vector signal generation and transmission scheme is proposed for mobile fronthaul networks based on dense wavelength division multiplexing (DWDM) and optical tandem single-sideband (OTSSB) modulation. At the distributed cell, two adjacent DWDM channels are divided into a group and both the frequency spacing of the adjacent optical carriers and the adjacent DWDM channels are 50 GHz in the system. A pre-distortion circuit is used for mitigating the modulation non-linearity. At an active antenna unit, when both two DWDM channels in a group are selected, six vector signals centered at different frequencies from 3.5 to 60 GHz are generated. When only one of the DWDM channels is selected, two vector signals centered at 16.5 and 33 GHz or two vector signals centered at 3.5 and 10 GHz can be generated. A simulation is performed to verify the proposed system and its performance by employing 16 quadrature amplitude modulation signals. In the simulation, the error vector magnitudes (EVMs) for different frequency vector signals are around 1% in the back-to-back case. When a section of 25-km single-mode fiber is inserted, the EVMs are still better than 5%.