Multi-Band All-Digital Transmission for 5G NG-RAN Communication

This paper explores multi-band all-digital transmitter architecture suitable for 5G next-generation radio access network (NG-RAN). In NG-RAN, most of the radio frequency (RF) layer functions are moved to a distributed unit (DU) in the digital domain so that a low cost and small size remote radio unit (RRU) can be developed. This paper presents a delta-sigma modulation (DSM) technique implemented in the field-programmable gate array (FPGA) for DU which is further interfaced with a power amplifier in RRU through feeder cable. A single bit 1st and $2^{\mathrm{n}\mathrm{d}}$ order low-pass DSM is implemented in FPGA of DU. An IQ sequencing block and high-speed serializer multiplexer are used to digitally up-convert the baseband signals to the different carrier frequencies in DU. The proposed scheme is validated with transmission of long-term evolution (LTE) signal of 5 MHz bandwidth for single as well as multi-band operation. The performance of the transmitter is measured in terms of signal to noise distortion ratio (SNDR) and error vector magnitude (EVM).