5G srsRAN End-to-End Reference Architecture with USRP

Application Note Number and Authors

AN-599

Authors

Bharat Agarwal and Neel Pandeya

Executive Summary

This Application Note presents a comprehensive reference design for deploying 5G NR Standalone (SA) systems using a hybrid open-source software stack: the srsRAN radio access network components and the OpenAirInterface (OAI) Core Network. This setup runs on NI/Ettus USRP radios, including the B210, enabling practical, low-cost, end-to-end 5G experimentation.

This configuration supports full 5G SA mode and enables complete end-to-end evaluation of the entire protocol stack, from the physical layer up to the core network.

Core Network Deployment Options

The OAI Core Network can be deployed in two modes:

• Single-machine deployment: CN and gNB run on the same machine — ideal for compact or portable test setups.
• Multi-machine deployment: CN is hosted on a separate machine — ideal for performance scaling or distributed 5G architecture evaluation.

UE Configuration Options

This reference architecture supports the following UE configurations:

• A software-defined UE implemented using srsUE with a USRP B210.
• A modem-based UE, such as Quectel or Sierra Wireless modules.
• A COTS 5G handset (e.g., Google Pixel 9) for interoperability and benchmarking.

Overview of the OpenAirInterface (OAI) Software Stack

The OAI) software provides a fully open-source and standards-compliant implementation of the 3GPP 5G New Radio (NR) protocol stack. It is designed to run in real time on commodity x86 hardware and interoperate with USRP software-defined radios.

Initially developed by Eurecom, a leading research institute in France, the project is now actively maintained by the OpenAirInterface Software Alliance (OSA) — a non-profit organization that promotes open wireless innovation and collaborative research.

OAI enables complete 5G system prototyping and research with implementations of:

• The gNB (next-generation base station)
• The UE (user equipment)
• The 5G Core Network (5GCN)

The OAI 5G NR stack is designed to:

• Operate in real time with USRP radios
• Support interoperability with commercial 5G NR handsets (e.g., COTS devices)
• Enable academic, experimental, and pre-commercial deployments

The OAI software stack is organized into multiple Git repositories, allowing modularity and collaborative development:

• OAI 5G Radio Access Network (RAN) Project:

 gitlab.eurecom.fr/oai/openairinterface5g

• OAI 5G Core Network (OAI-CN):

 gitlab.eurecom.fr/oai/cn5g

OAI source code is freely available for non-commercial and academic research use. Licensing details and additional documentation are available on the OpenAirInterface website.

Overview of srsRAN

srsRAN (Software Radio Systems Radio Access Network) is an open-source 4G and 5G software suite developed by Software Radio Systems Ltd. (SRS). It enables researchers, developers, and network engineers to deploy and experiment with end-to-end wireless communication systems. The suite provides modular components for building complete Radio Access Networks (RANs) and supports both 4G LTE and 5G NR (New Radio).

Key Components of srsRAN 5G

The srsRAN 5G stack is composed of several main components:

• srsRAN gNB: Implements the 5G NR base station (gNodeB), including PHY, MAC, RLC, PDCP, and NGAP layers. Supports standalone (SA) mode and connects to a 5G Core Network via NG interfaces.
• srsUE: A 4G LTE software user equipment used primarily for legacy LTE research. The 5G UE is under active development and partially supported.
• srsEPC (for LTE): The Evolved Packet Core for 4G LTE deployments. In 5G, this is replaced by external 5G Core Network solutions such as OAI-CN5G or commercial alternatives.
• srsGUI and nrscope: Tools for real-time visualization and debugging of signal and protocol layer performance.

Supported Features

• 5G NR Standalone (SA) mode operation (Release 15+)
• Configurable numerology, bandwidth, and frame structure
• Support for USRP hardware (e.g., B210, N3xx, X410)
• Dynamic scheduling, HARQ, and experimental beamforming
• Compatibility with open-source 5G Core solutions (e.g., OAI-CN5G)

Use Cases

srsRAN is widely used for:

• Academic research and prototyping
• 5G network testing and benchmarking
• Private network deployments
• SDR-based teaching and training environments

Licensing and Community

srsRAN is released under the AGPLv3 license, making it freely available for modification and redistribution under open-source terms. The project is actively maintained and supported by a growing developer community on platforms such as GitHub and GitLab.

Overall, srsRAN provides a robust and flexible platform for 4G/5G experimentation and serves as a valuable resource for researchers working in wireless communications.