A 66-Gb/s/5.5-W RISC-V Many-Core Cluster for 5G+ Software-Defined Radio Uplinks

Following the scale-up of new radio (NR) complexity in 5G and beyond, the physical layer’s computing load on base stations is increasing under a strictly constrained latency and power budget; base stations must process <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gt$</tex-math> </inline-formula> 20-Gb/s uplink wireless data rate on the fly, in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lt$</tex-math> </inline-formula> 10 W. At the same time, the programmability and reconfigurability of base station components are the key requirements; it reduces the time and cost of new networks’ deployment, it lowers the acceptance threshold for industry players to enter the market, and it ensures return on investments in a fast-paced evolution of standards. In this article, we present the design of a many-core cluster for 5G and beyond base station processing. Our design features 1024, streamlined RISC-V cores with domain-specific FP extensions, and 4-MiB shared memory. It provides the necessary computational capabilities for software-defined processing of the lower physical layer of 5G physical uplink shared channel (PUSCH), satisfying high-end throughput requirements (66 Gb/s for a transition time interval (TTI), 9.4–302 Gb/s depending on the processing stage). The throughput metrics for the implemented functions are ten times higher than in state-of-the-art (SoTA) application-specific instruction processors (ASIPs). The energy efficiency on key NR kernels (2–41 Gb/s/W), measured at 800 MHz, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${25}~^{\circ } $</tex-math> </inline-formula>C, and 0.8V, on a placed and routed instance in 12-nm CMOS technology, is competitive with SoTA architectures. The PUSCH processing runs end-to-end on a single cluster in 1.7 ms, at <6-W average power consumption, achieving 12 Gb/s/W.