Spirent: Timing and Synchronization for 5G Open RAN Networks

Posted on02/05/2021

It is impossible to ignore the current waves in the telecoms industry caused by the emergence of Open RAN. An ever-increasing number of major telecoms operators and vendors are moving to support the splitting of (previously integrated) network solutions and platforms into interoperable Whitebox hardware, middleware/Operating Systems, and software or virtual network functions (VNFs).

The Radio Access Network (RAN) can particularly benefit as a result, as network operators will choose optimized hardware and software solutions from a range of incumbent and new vendors to meet the specific needs of their network.

Despite these advantages, guaranteeing performance and managing complexity are inherent challenges of this new approach. In practice, the responsibility for validating and deploying systems will fall on network operators themselves – either directly, or through partnerships with Systems Integrators (SI).

The need for timing and synchronization

It should be noted that as Open RAN networks are intended to deliver the full range of enhanced capabilities available with 5G New Radio, the fundamental need for the network to deliver highly accurate synchronization (using Precision Time Protocol and Synchronous Ethernet) remains.

Often network operators require network equipment to meet strict timing requirements, such as ITU-T G.8273.2 Class-C specifications, with each device delivering nanoseconds level timing performance.

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The combination of these specific timing requirements and the additional complexity of multi-vendor environments means it is critical to be able to identify and validate all aspects of network timing performance.

Synchronization plane (S-plane) has been identified as a key aspect of O-RAN specifications, with requirements defined in the working groups for Fronthaul, Open Interfaces and Transport.

The additional complexity of multi-vendor environments means it is critical to be able to identify and validate all aspects of network timing performance.

The devil is in the details

When it comes to validating network timing performance, “the devil is in the details," with synchronization a foundational element, affecting multiple functions distributed throughout the network as well as having a direct impact on radio performance.

O-RAN is used by 3GPP for radio specifications, and ITU-T and IEEE for ‘transport’ standards: in all cases this includes definition of synchronization requirements.

Open RAN is made possible through standardized open network interfaces, defined in 3GPP (radio specifications), O-RAN Alliance, ITU-T and IEEE (transport standards) among others.

All in all, it is vital to take a holistic view of the specifics of S-plane, as identified in the multiple areas of O-RAN specifications, as well as the fundamental timing requirements defined in ITU-T, which provide the building blocks and help determine how the S-plane requirements of ITU-T, O-RAN and 3GPP interact. These specifications must be considered when creating a comprehensive plan for testing synchronization performance of devices and systems, in a way that reflects related complexity.

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Stay tuned for additional insights around the timing and synchronization considerations for 5G Open RAN Networks.

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