A single-chip Split-6 PHY implementation for 5G NR, using RFSoC and PYNQ

Indoor traffic has been estimated to account for over 70% of all mobile data in urban areas. We propose a small cell Split-6 radio unit (RU) to meet the indoor use case, presenting a hardware implementation of the physical layer Physical Downlink Shared Channel, targeting an AMD UltraScale+ Radio Frequency System on Chip (RFSoC) device. Several custom IP cores are developed and used in conjunction with integrated resources available on the target RFSoC chip. The design uses less than 10% of Block RAM memory, and under 3% of other available Programmable Logic resources; meeting timing at 122.88 MHz, enabling 100 MHz bandwidth channels. This modest resource utilisation leaves capacity for integration of other physical layer channels. Total power of 4.33 W and dynamic power of 2.533 W confirm that the baseband RFSoC power draw is very low. A test harness developed using the PYNQ software/hardware framework is presented, which provides a low-complexity approach to radio testing without external network software. The PYNQ system provides a user interface to update resource allocation in real time, and produces resource grid and constellation plots based on data captured from the design operating on the target RFSoC4x2 development board. The system is tested through two case studies, validating each sub-step of the physical layer. Latencies of 0.332 ms and 0.719 ms, with a 122.88 MHz clock, meet key HARQ requirements. The success of the study confirms RFSoC devices as candidates for small cell Split-6 deployment.