5G srsRAN End-to-End Reference Architecture with USRP
Contents
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.
Overview of the Reference Architecture
The OAI USRP Reference Architecture enables researchers, developers, and system integrators to build complete 5G NR systems using open-source software and commercial SDR hardware. This section outlines two typical deployment modes of the architecture:
- A compact, single-host configuration for integrated lab setups
- A modular, distributed configuration for scalable experimentation
Each mode supports connectivity to a diverse range of User Equipment (UE), including Quectel 5G modules, USRP-based UEs, and commercial handsets such as the Google Pixel 9 with an open SIM.
Deployment 1: OAI gNB and CN on the Same Machine
In this setup, both the OAI Core Network (CN) and the OAI NR gNB are hosted on the same physical machine. This configuration is typically used for:
- Lab-based research and teaching environments
- Portable demos and proof-of-concept systems
- Quick-start testbeds for 5G protocol stack development
Architecture Highlights:
- Compute Node: High-core-count x86 server (e.g., Intel Xeon w7-2495X, 24 cores)
- Operating System: Ubuntu 22.04
- Software Stack: OpenAirInterface gNB (monolithic) and 5G Core (AMF, SMF, UPF, NRF, etc.)
- UHD Version: 4.8
- RF Front-End: USRP X410 with SFP+ (10/100 Gbps) link
Advantages:
- Simple setup with fewer network dependencies
- Easy to debug and deploy
- Lower hardware requirements
Limitations:
- Less suitable for high-throughput traffic testing
- Shared CPU and I/O resources may limit performance
Deployment 2: OAI gNB and CN on Separate Machines
This configuration separates the OAI gNB and CN onto two dedicated physical systems connected via an Ethernet switch. It is ideal for:
- Research involving modular network slicing, edge cloud integration, or realistic RAN-Core interface behavior
- Scalable testbeds with high-throughput and isolated workloads
- Large MIMO, beamforming, or MEC-based deployments
Architecture Highlights:
- gNB Node: Intel Xeon w7-2495X, 24 cores, Ubuntu 22.04
- CN Node: Separate x86 server, also running Ubuntu 22.04
- Interconnect: High-speed Ethernet via managed switch
- RF Front-End: USRP X410 with dual SFP+ for IQ data
Advantages:
- Higher reliability and scalability
- Easier to simulate real-world latency, routing, and interface constraints
- Better performance profiling of CN and gNB independently
Considerations:
- Requires correct IP addressing, routing, and DNS setup
- More complex to configure and monitor
