Understanding O-RAN Open Fronthaul: A Key to Multi-Vendor 5G Networks
O-RAN Open Fronthaul: Facilitating Multi-Vendor Interoperability in 5G Networks
As 5G deployments expand, it is not just a matter of deploying infrastructure, it is the vendors and their ecosystem. Operators are moving away from vendor-locked, proprietary solutions towards open, disaggregated architectures. One of the main tenets of this change is the O-RAN Open Fronthaul a common interface that enables the use of multiple vendor solutions to work together.
The image shows an example of this architecture in a real world example: O-RUs from Vendor A connected via open fronthaul to an O-DU from Vendor B, all deployed with in a cell site environment. For the purposes of this article, we will explain how open fronthaul can make a difference in how radio access networks embrace flexibility and innovation in support of 5G.
What is O-RAN Open Fronthaul?
O-RAN (Open Radio Access Network) is an industry initiative to open up a typically closed ecosystem in radio access networks. The Open Fronthaul interface is one of the most important elements of O-RAN, and it connects two components in the RAN architecture. The two components are:
O-RU (Open Radio Unit) – the equipment that transmits and receives RF
O-DU (Open Distributed Unit) – the equipment that does the real time baseband processing
This interface provides a means of replacing proprietary RUs and DUs and taking away any hidden links to upstream components, with standardized protocols and open specifications that help provide:
Multi-vendor interoperability
Cheaper cost
Greater flexibility in deployment
Main Elements in the Image
Element Functionality in Architecture
O-RU (Open Radio Unit) Provides Layer 1 (PHY-low) RF functionality, which includes analog/digital conversion, filtering, and connection to the antenna.
O-DU (Open Distributed Unit) Provides real-time Layer 1 (PHY-high) processing and Layer 2 processing including MAC, RLC, and part of PHY.
Open Fronthaul Interface Provides the connection of the O-RU to the O-DU, using specifications defined in O-RAN (usually Option 7.2x split).
Transport Network Provides the connection between the O-DU to either the Central Unit (CU) or core network, to perform additional processing and forwarding.
Why Open Fronthaul is Important
- Multi-Vendor Environment
Operators can use O-RUs and O-DUs simultaneously provided by different vendors. This prevents vendor lock-in and allows for innovation. - Flexible Deployment
Open fronthaul is able to support many types of network configurations:
Macro cells
Small cells
Private 5G deploys
3. Cost Efficiency
Commercially available off-the-shelf (COTS) hardware and open interfaces help to lower both CAPEX and OPEX.
- Faster Innovation
With open APIs and standardized specifications, smaller vendors or startups can innovate faster without having to necessarily own the entire stack.
O-RAN Fronthaul Interface: Technical Specifications
Specification Description
Split Option Option 7.2x (PHY split between RU and DU)
Transport Protocol eCPRI or IEEE 1914.3
Timing Synchronization IEEE 1588v2 (PTP), SyncE
Deployment Use Cases
Use Case Benefits of Open Fronthaul
Urban Macro Cells: Supports Massive MIMO, high-capacity RUs from several vendors
Private 5G for Industry: On-premise O-DU with RUs that meet industrial needs
Multi-Operator RAN: Shared infrastructure while retaining vendor freedom
Rural Expansion: Reduced cost to expand coverage with available off-the-shelf interoperable hardware.
Challenges & Considerations
The open fronthaul of O-RAN will result in benefits and complexities:
Interoperability Testing: Ensuring the interoperability and communication of vendor products.
Latency and Jitter: Fronthaul networks must address previously-determined timing requirements for the O-RUs.
Security and Management: Open interfaces provide opportunities for increased attack surface and require a management system.
Conclusion
The O-RAN Open Fronthaul is a key component of next generation, disaggregated RAN architecture. Standardizing the link between O-RUs and O-DUs will allow operators to build more flexible, scalable and cost efficient 5G networks not tied to a vendor.
An open fronthaul motivates more collaboration, more competition, and more customization opportunities for mobile networks.
Lessons Learned: Deploying O-RAN Open Fronthaul into Real Networks
An effectively implemented open fronthaul architecture based on O-RAN standards is a multi-faceted approach that considers both technical and operational factors:
- Hardware Compatibility
Ensure the O-RUs and O-DUs support Option 7.2x (or the functional split being used).
Make sure O-RUs and O-DUs conform to the O-RAN Fronthaul specifications (O-RAN WG4).
Use SFP+ or QSFP modules compatible with the transport bandwidth (10G/25G/100G) expected.
- Software Stack
Deploy an O-DU supporting:
-RLC, both MAC and PHY-high functions
-Timing synchronization mechanisms
-Real-time Linux / DPDK accelerated user space.
Some suppliers also have DU software in containers for cloud-native deployments. - Fronthaul Network Requirements
Latency Budget: <250μs (typical for Option 7.2x)
Jitter: <65ns
Sync: IEEE 1588v2 PTP and SyncE
Redundancy: preferably ring or mesh for reliability
Industry uptake: Who is using O-RAN open fronthaul?
Globally, operators leading the way:
Rakuten Mobile (Japan): 1st full-scale commercial deployment of O-RAN
Dish Wireless (USA): Building out a cloud-native 5G network; using O-RAN and open fronthaul
Telefonica & Vodafone (Europe): Trialing in urban and rural contexts to test interoperability and performance.
The vendor ecosystem:
O-RU suppliers O-DU suppliers
Fujitsu, NEC, MTI Altiostar, Mavenir, Radisys
Comba, Baicells Parallel Wireless, Samsung
These vendors are collaborating within the O-RAN Alliance to ensure conformity, testing and overall ecosystem maturity.
Future Vision: Why Open Fronthaul Is The Future of RAN
✅ Disaggregation is a Faster Approach to Innovation
Vendors can focus on their strengths, e.g., one supplying high-performing RUs, another developing smart DUs, rather than needing to offer complete end-to-end stacks.
✅ Cloud-Native Roadmap
As RAN functions move toward containers and edge clouds, O-RAN mirrors the telecom industry's journey toward virtualization and orchestration using platforms such as Kubernetes, ONAP, and O-RAN SMO.
✅ AI-Enabled RAN Operations
With its RAN architecture model, O-RAN enables the integration of RAN Intelligent Controllers (RIC) which leverages automation, closed-loop optimization and AI into RAN network management.