What is OpenAirInterface?

OpenAirInterface (OAI) is an open-source software platform that enables users to build and operate complete 4G LTE and 5G New Radio (NR) cellular networks. Fully compliant with 3GPP standards, OAI allows real, working mobile networks to be deployed using standard servers and radio hardware, without the cost and restrictions of proprietary telecom systems.

Originally developed by EURECOM and now maintained by the OpenAirInterface Software Alliance (OSA), OAI is widely used for research, testing, private networks, and early-stage commercial deployments. Its software-based architecture provides deep visibility and control over network behavior, making it a popular platform for innovation in wireless communications.

How OpenAirInterface Works

OAI runs on general-purpose x86 computers combined with software-defined radios (SDRs) and commercial radio units. All key cellular network functions are implemented in software, allowing users to inspect, modify, and extend the network at every layer of the protocol stack.

Unlike closed “black-box” solutions from traditional vendors, OAI exposes the internal workings of the radio access network and core network. This flexibility makes it possible to experiment with new algorithms, test emerging 3GPP features, and customize networks for specific applications.

The platform supports real-time operation with commercial user equipment (UE), including smartphones and data modems, demonstrating that OAI is not limited to simulation environments but can operate as a real cellular network.

Core Components of the OAI Platform

OpenAirInterface consists of three main components that together form a complete end-to-end cellular network:

• Radio Access Network (RAN): The RAN implements 4G eNodeB and 5G gNodeB base station functions, handling radio transmission, scheduling, and mobility management.
• Core Network: OAI provides both a 4G EPC and a 5G standalone core, managing user authentication, session control, mobility, and data routing.
• Operations and Maintenance (OAM): OAM tools support network monitoring, configuration, and troubleshooting, enabling users to manage and optimize deployed networks.

Supported Standards and Technologies

Frequency Bands: OAI primarily supports Frequency Range 1 (FR1), covering sub-6 GHz spectrum. Well-tested bands include n40, n41, n77, and n78, with band n78 (3.3–3.8 GHz) being widely used for private and experimental 5G deployments. Support for mmWave (FR2) is under development. Flexible frequency configuration also enables non-standard and experimental deployments.

4G LTE Support: OAI supports 4G LTE specifications from 3GPP Release 8 through Release 10 across the protocol stack. It supports both FDD and TDD duplex modes, channel bandwidths of 5, 10, and 20 MHz, and MIMO configurations up to 2×2. These capabilities allow interoperability with commercial LTE devices and test equipment.

5G New Radio Support: For 5G NR, OAI implements key RRC procedures according to 3GPP Release 16 and supports both standalone (SA) and non-standalone (NSA) deployment architectures. The platform supports TDD and FDD operation, bandwidths up to 100 MHz, and MIMO configurations up to 4×2, with downlink modulation up to 256-QAM.

Key Features and Capabilities

Real-Time Performance: OAI is written in C and optimized for real-time Linux operation on x86 and ARM platforms. It meets 3GPP timing requirements and has been validated with commercial smartphones and USB modems.

Hardware and SDR Support: The platform supports a wide range of SDR hardware, including Ettus USRP B-, N-, and X-series devices, as well as LimeSDR platforms, giving users flexibility in RF front-end selection.

Development and Debugging Tools: OAI includes emulation modes for testing without RF hardware, along with protocol analyzers, performance profilers, logging tools, and debugging utilities. These features simplify development and accelerate experimentation.

Flexible Deployment Models: OAI supports monolithic and disaggregated RAN architectures, multiple deployment modes, and configurable parameters across PHY, MAC, and higher layers. Network functions can be deployed at the edge, in data centers, or in cloud environments.

Virtualization and Containerization: Core network functions are containerized using Docker and follow cloud-native principles, enabling scalable and flexible deployments in centralized or distributed environments.

Deployment Scenarios and Use Cases

Research and Academic Testbeds: OAI is widely used in universities and research labs for studying advanced wireless topics such as network slicing, beamforming, edge computing, and 5G positioning techniques.

Private 5G Networks: Enterprises use OAI to deploy private 5G standalone networks for industrial automation, smart factories, and enterprise connectivity, with support for URLLC and customized QoS.

Network Testing and Validation: Vendors and operators use OAI for protocol testing, interoperability validation, and early evaluation of new 3GPP features before commercial rollout.

Cloud-RAN and Edge Computing: OAI enables Cloud-RAN experimentation by running baseband processing on commodity servers. It also supports edge computing use cases requiring low latency, such as real-time analytics and industrial IoT.

Education and Spectrum Research: OAI is widely used for hands-on training in cellular technologies and for research into spectrum sharing, cognitive radio, and dynamic spectrum access.

Advantages and Limitations

Advantages

• Open-source, low-cost alternative to proprietary systems
• Full 4G and 5G end-to-end network support
• Strong community and academic backing
• Deep visibility and control over protocol layers
• Suitable for research, testing, and private networks

Limitations

• Steep learning curve due to system complexity
• Specific hardware and real-time configuration requirements
• Commercial use requires patent and licensing considerations
• Integration with existing networks may require significant effort

OpenAirInterface bridges the gap between academic research and real-world cellular deployment. By providing an open, standards-compliant platform covering the RAN, core network, and management layers, OAI enables experimentation, validation, and deployment of 4G and 5G networks on real hardware. As wireless technology evolves toward future generations, OAI remains a critical tool for engineers, researchers, and organizations developing the next wave of cellular innovation.