The O-RAN Alliance, a global community driving the open radio access network (O-RAN) ecosystem, has released a report evaluating multiple spectrum aggregation techniques.
Initiated and led by Mavenir, the report delves into the technical intricacies of interconnecting Open Distributed Units (O-DUs) for carrier aggregation in multi-vendor deployments.
The report highlights the need for a dedicated interface between O-DUs to enable efficient spectrum aggregation—a key feature that allows operators to combine multiple frequency bands to deliver faster data speeds and improved coverage.
Such a capability is particularly crucial as operators obtain new spectrum during regulatory spectrum sales over time, creating a strong desire to combine new spectrum with existing spectrum using carrier aggregation.
Supporting multi-vendor spectrum aggregation
This “Inter O-DU” solution necessitates a new signalling protocol and management framework to facilitate tasks such as establishing connections, allocating resources, and synchronising operations across geographically dispersed units.
“A new interface connecting multiple O-DUs needs to be defined for supporting spectrum aggregation. This requires defining a management interface for tasks such as to establish and maintain O-DU relations, and SCell associations,” the report states.
The report acknowledges the complexity inherent in developing this solution, emphasising the need to carefully consider bandwidth requirements, latency constraints, and potential impact on existing operational processes:
“The bandwidth and latency requirements and their impact on performance of carrier aggregation also needs to be evaluated in detail at WI phase,” the report explains.
Currently, no open standardised interface exists for carrier aggregation between two vendors, creating vendor lock-in for operators in all future spectrum expansions. While proprietary interfaces for carrier aggregation have existed since LTE days and are well understood for implementations, attempts to standardise an open interface in bodies such as 3GPP have been unsuccessful due to resistance from traditional vendors.
Benefits and mitigating risks
By enabling seamless interoperability between O-DUs, operators can unlock significant advantages, including:
- Enhanced performance: Spectrum aggregation allows for greater spectral efficiency, potentially resulting in faster data speeds and improved user experience.
- Increased capacity: Combining multiple frequency bands can accommodate a larger number of users, boosting network capacity and supporting growing demand.
- Expanded coverage: The report suggests that inter O-DU CA could leverage lower frequency bands for uplink traffic, extending the reach of high-frequency carriers and improving coverage in remote areas.
- Vendor independence: Operators gain freedom from incumbent vendors, improving their negotiating power and control over network evolution.
- Future-proofing: The open specification provides a pathway for new low-latency features and services for 6G by enabling real-time communication between DUs.
The report stresses the importance of mitigating potential risks. It underscores the need to minimise disruption to existing O-RAN architecture, avoid introducing new requirements on 3GPP specifications, and ensure that security is addressed throughout the design process.
“If new interface(s) are defined, the security and integrity of data transfer over the interface are to be protected as specified by O-RAN WG11. The impact of the security requirements on the equipment and the underlying transport needs to be assessed,” the report states.
Dr Sridhar Rajagopal, SVP of Access Technologies at Mavenir and rapporteur for the technical report, said: “This report from the O-RAN Alliance, with its welcome set of recommendations on multi-vendor carrier aggregation, could not come at a more pivotal time for Open RAN as spectrum discussions continue for expanding 5G deployments and with 6G on the horizon.
“Standardising the interface between DUs for multi-vendor carrier aggregation will remove single vendor stickiness and will be a game changer for Open RAN.”
The proposed standardisation represents another step towards breaking down vendor lock-in barriers and fostering a more open and competitive telecoms ecosystem.
A full copy of the report can be found here (PDF)
See also: NEC and Cisco launch enterprise private 5G solution
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