Clarity on O-RAN Specification Updates for Massive MIMO Radios

Evolved Open RAN Fronthaul Evolution

Specification work within the O-RAN Alliance in regard to an uplink modification to open fronthaul for Massive MIMO radios is ongoing and should produce a final specification next year. The initial steps were taken at the O-RAN Alliance event in Osaka, Japan, in June 2023, to establish the uplink performance improvement (ULPI) specification. At this meeting two solutions were accepted and taken forward into the specification process.

Today, there is what is termed 7.2 CAT A simple radio, and 7.2 CAT B interfaces for Massive MIMO specified in the O-RAN alliance specifications. Following the Osaka meeting, there are two new interfaces suggested which have the extension “ULPI,” and one option moves the equalizer from the compute DU to inside each radio on the tower.

There is still a lot of work to do in completing the specification, and at this time is only applicable to Massive MIMO. Simple radios such as 4T4R, Dual band and Triple band would still use CAT A interface.

The challenge for DU vendors is to support all four interfaces on the DU, which Mavenir is committed to do.

If the operator chooses a DU supplier that does not support all interfaces, they will be locked to that supplier. But with Open RAN they have the option to buy another vendor’s DU that supports all interfaces.

It’s important that equipment be backward compatible with the CAT A and CAT B interfaces. If the solution is essentially software, interfaces can be deployed fairly quickly. Although there may be a preference for the new ULPI interfaces, the O-RAN Alliance says open RAN products must support existing CAT A and CAT B on the DU.

The real issue is to make sure that the DU, over time, is upgradable and supports all interfaces. Suppliers are going to have to grapple with it because the product is going to have to be certified as O-RAN compliant.

Open RAN Radios
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