The O-RAN Alliance is working on an uplink modification to open fronthaul for Massive MIMO radios to improve uplink performance. At a recent meeting in Osaka, the Alliance approved moving the equalizer from the distributed unit (DU) to inside each radio unit on the tower.
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. “There is still a lot of work to do in completing the specification, and, at this time, only applicable to Massive MIMO simple radios such as 4T4R, Dual band and Triple band would still use CAT A interface,” said Mavenir’s John Baker, SVP, Ecosystem Business Development.
The Open RAN standard requires the radio unit, the distributed unit and the centralized unit of the network to be separated. Ericsson, which made headlines as the selection of AT&T for O-RAN, supports splitting up of components required by Open RAN, according to Mobile-Experts Principal Joe Madden. Ericsson supports putting more processing power into each of those components. The OEM’s version has more baseband processing residing in the radio unit.
“Ericsson prefers to do more real time processing in the radio, which would be less desirable if you had to break the radio into two pieces and you had a delay in between,” Madden said. “This way, Ericsson can fulfill their promise to the operators to support Open RAN, but use their muscle to push the Open RAN community into something that they can compete better on.”
Mavenir is one of the DU vendors that support multiple interfaces on the DU, according to Baker, to ensure that MNOs are not locked into one supplier.
“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,” Baker said.
By J. Sharpe Smith, Inside Towers Technology Editor