FPGA Implementation of a 4G/5G Multimode DU Downlink Transmission Chain

This paper presents a multimode Distributed Unit (DU) transmission chain implemented in Field-Programmable Gate Array (FPGA). A careful analysis is taken towards the physical layer differences between Fourth Generation Long-Term Evolution (4G-LTE) and the Fifth Generation New Radio (5G-NR) of mobile networks to determine the fundamental changes in each generation's DU architecture. The DU supports both 4G-LTE and 5G-NR to be modulated parallely in real-time, and is developed in this work by using high level tools and Register-Transfer Level (RTL) code, from Matlab and Simulink to VHDL, to obtain the final implementation of a single DU. On the 4G side, the DU supports the maximum LTE channel bandwidth of 20 MHz, and the 5G counterpart supports a channel bandwidth from 5 MHz to 100 MHz. The results are validated in Matlab, Simulink, RTL and in real-time, culminating in a final FPGA implementation, with an EVM of 0.24% for 4G and 1.60% for 5G.