Open RAN is an approach to building the radio access network (RAN) of a mobile network from disaggregated, interoperable components connected by open, standardized interfaces, so that radios, baseband software and control functions can come from different vendors. In telecommunications, it challenges the traditional model in which one supplier delivers the entire RAN as a closed, integrated system.
Open RAN is closely tied to the evolution of 6G & future networks, because its software-defined, cloud-native and programmable design is seen as a foundation for AI-native network control. The specifications most associated with it come from the O-RAN Alliance, building on functional splits defined by 3GPP.
How Open RAN disaggregates the radio access network
Open RAN separates the base station into three main functional units. The radio unit (O-RU) handles radio frequency processing and the antenna connection, the distributed unit (O-DU) runs real-time baseband processing, and the central unit (O-CU) handles higher-layer protocols that are less time-critical.
The key element is the open fronthaul, the interface between the radio unit and the distributed unit. The O-RAN Alliance specifies it using the 7.2x functional split, which divides the physical layer between the two units and allows a radio from one vendor to work with baseband software from another.
The choice of split is a trade-off between radio simplicity and fronthaul load. Moving more processing into the radio unit lowers the bandwidth the fronthaul must carry, while keeping more in the distributed unit allows centralized coordination of several cells. Split 7.2x was chosen as a compromise that keeps radios relatively simple yet avoids the very high bit rates of the older CPRI interface, which transported raw radio samples and was largely proprietary in practice. Fronthaul links must also meet tight latency and synchronization budgets, usually in the range of a few hundred microseconds one way.
| Component | Function | Typical deployment |
|---|---|---|
| O-RU (radio unit) | RF processing, lower physical layer | At the antenna site |
| O-DU (distributed unit) | Upper physical layer, MAC, RLC in real time | Cell site or edge data center |
| O-CU (central unit) | PDCP and RRC, split into control and user plane | Regional or central cloud |
| Near-RT RIC | Control loops from about 10 ms to 1 s | Edge cloud |
| Non-RT RIC | Policy and model training above 1 s | Service management platform |
The RAN intelligent controller and xApps
The most distinctive Open RAN addition is the RAN intelligent controller (RIC), a platform that lets software applications optimize the network. The near-real-time RIC hosts xApps that act on timescales between roughly 10 milliseconds and one second, while the non-real-time RIC hosts rApps that work over longer periods and train models.
Through the RIC, operators can introduce functions such as traffic steering, interference management, energy saving and anomaly detection from third-party developers rather than waiting for the baseband vendor’s roadmap. This programmability is a major reason Open RAN is discussed as a step toward AI-driven radio management.
| Loop | Timescale | Example use |
|---|---|---|
| Real-time loop in the O-DU | Below 10 ms | Scheduling and beamforming |
| Near-real-time loop (xApps) | About 10 ms to 1 s | Traffic steering, interference control |
| Non-real-time loop (rApps) | Above 1 s | Energy policies, model training |
Open RAN compared with related architectures
Open RAN overlaps with several neighboring ideas and is often used loosely. The precise distinction concerns which interfaces are open and whether components from different vendors can actually be combined.
| Approach | Key characteristic | Multi-vendor at the fronthaul |
|---|---|---|
| Traditional RAN | Integrated hardware and software from one vendor | No |
| Virtualized RAN (vRAN) | Baseband software on general-purpose servers | Not necessarily |
| Cloud RAN | vRAN with cloud-native, containerized functions | Not necessarily |
| Open RAN | Open interfaces between disaggregated units | Yes, by design |
| Single-vendor Open RAN | O-RAN-compliant interfaces, one supplier initially | Possible later |
The table shows that virtualization and openness are different properties. A virtualized RAN can still be closed, and an Open RAN deployment can initially use one vendor for all parts while keeping the option to add others later.
Benefits operators expect
Operators pursue Open RAN mainly for supplier diversity and flexibility. A smaller set of large equipment vendors has dominated the RAN market, and open interfaces aim to lower vendor lock-in and let new entrants compete in specific components.
- Supply chain resilience: replacing one component does not require replacing the whole RAN.
- Innovation speed: third-party xApps and rApps add features independently of hardware cycles.
- Cost structure: commercial off-the-shelf servers and competition may reduce costs over time.
- Automation: open data and control interfaces enable closed-loop optimization.
- Policy goals: several governments support Open RAN for security and industrial reasons.
Challenges and open questions
Open RAN moves complexity from the vendor to the operator or a systems integrator. Combining components from several suppliers requires extensive interoperability testing, and responsibility for faults can become unclear when performance degrades.
| Challenge | Why it matters | Typical mitigation |
|---|---|---|
| System integration | Many vendors, many interfaces | Prime integrator or pre-validated blueprints |
| Energy efficiency | General-purpose processors may consume more power | Hardware accelerators and smart sleep modes |
| Performance parity | Massive MIMO radios are demanding | Mature accelerator cards and joint testing |
| Security surface | More open interfaces to protect | Zero-trust design and interface encryption |
| Fronthaul requirements | Strict latency and timing | Dedicated fiber and precise synchronization |
Commercial results are mixed. Some greenfield operators have built nationwide networks on Open RAN principles, while large incumbents often adopt it gradually, starting with O-RAN-compliant interfaces from existing suppliers. Whether full multi-vendor operation at scale becomes the norm remains an open question for the coming generation of networks.
Explained without jargon
A mobile network uses base stations to connect phones by radio. Traditionally, each base station came as a sealed package from one company, so operators had to buy every part from that same supplier.
Open RAN changes this by agreeing on common plugs and rules between the parts. It is like a desktop computer where the monitor, keyboard and graphics card can come from different makers because the connections are standardized. Operators gain more choice and flexibility, but they also take on more work to make everything fit together.
A typical use case
A regional mobile operator needs to expand coverage to about 400 rural sites and wants to avoid depending on a single equipment supplier. It selects radio units from one vendor, baseband software running on commercial servers from another, and a near-real-time RIC from a third, all connected through the O-RAN 7.2x fronthaul.
A systems integrator validates the combination in a lab before rollout. After deployment, the operator installs an energy-saving xApp that switches off selected carriers during low-traffic night hours. The operator gains a second sourcing option for every component and lowers night-time energy use at those sites, while accepting a longer testing phase and a larger in-house integration team.