Cloud RAN platforms – Why are vendors adopting different Layer-1 acceleration strategies?

CSPs are showing an increasing interest in leveraging the benefits of RAN virtualization and cloud-native technologies and vendors are responding to this demand. As a result, future RAN networks are expected to evolve gradually towards Cloud RAN based solutions, which will be deployed alongside traditional, proprietary 5G networks.

In contrast to traditional RAN networks, the baseband unit of a cloud RAN base station is split into two units: a Distributed Unit (DU) and a Centralized unit (CU). Today, the vast majority of commercially deployed DU basebands run on x86 processors. However, alternatives to Intel’s x86 platform, based on ASICs, GPU and RISC-V architectures are expected to become widely available during the next three years.

Cloud RAN platforms typically use PCIe-based accelerator cards to process the compute-intensive Layer 1 workloads. There are essentially two types of accelerator architecture: look-aside and in-line:

• Look-aside accelerators offload a small subset of the 5G Layer 1 functions, for example, forward error correction, from the host CPU to an external FPGA-based accelerator.
• With an in-line accelerator card, all the Layer 1 data passes directly through the accelerator and is processed in real-time – a critical requirement for Layer 1 workloads. This processing is done by other processor types, for example, ARM or RISC-V based DSPs.

However, there is a marked difference in the approach of vendors towards Layer 1 acceleration, with some vendors supporting the look-aside option, some supporting the in-line option, while others plan to offer both options. Counterpoint Research