Small cell innovation from Vodafone and Mavenir (and BT?)

Mavenir small cell in-building solution for Vodafone mirrors earlier trial work with BT Wholesale, and a rival's solution for Rakuten.

Mavenir and Vodafone have said that they have designed an Open RAN small cell product for business customers.

The solution is intended to provide 4G coverage and capacity in medium to large venues. Vodafone said, “The simple plug and play installation means coverage can be instantly deployed, enabling seamless connectivity for every device in the office.” 

As the product comes to market, it’s notable that this looks very similar to a product design that Mavenir was developing two years ago with BT. 

At that time, in a demo reported by TMN, Mavenir and BT were talking about a combined Radio Unit and Distributed Unit (RU-DU) made by Sercomm, with Mavenir vRAN software running on the CU and the DU part of the combined RU-DU.

This Vodafone product sees, guess what, a combined Radio Unit and Distributed Unit (RU-DU) made by Sercomm, with Mavenir vRAN software running on the CU and the DU part of the combined RU-DU. 

One big difference is that BT Wholesale and Mavenir were exploring the vCU and DU-RU as a multi-operator solution, hosted by BT Wholesale. The Vodafone deployment is not that, but it does seem to be a live market application of a similar design. 

There are other applications of this sort of product in the market, proving the Open nature of Open RAN .

TMN understands Sercomm is using Qualcomm’s FSM 9016 chipset for its design. That’s the small cell chipset that Sercomm used as it partnered with Altiostar to develop a vRAN small cell solution that went on to debut in Rakuten’s network in Japan. The Sercomm-Altiostar-Rakuten deployment looks quite similar to the Sercomm-Mavenir-Vodafone plan.

In Rakuten’s case it said it would be able to migrate from the 4G small cell to 5G by updating the DU part of the build. Vodafone also said that the small cells would supply 4G “initially” – clearly hinting at a 5G upgrade path. It also added that the disaggregated elements of the solution would be able to interface with products from other vendors. 

That all looks like validation for the Open RAN principles of supporting the operator’s vendor-of-choice, and Vodafone called out multi-vendor capability of indoor Open RAN in its release for this product. Previously the operator has partnered with SpiderCloud (now Corning) to offer enterprises a solution for covering similar sized office spaces.

Splits if you care

Mavenir has confirmed to TMN that the small cell architecture is based on 3GPP functional Split Option 2.

That’s the same split that BT and Mavenir were exploring in 2019. As we said, the idea at that time was to enable BT Wholesale to operate a neutral host model for MNOs, with CUs in just a very few centralised locations, and the enterprise DU-RUs connected via its fibre in business locations. BT reckoned it could cover the whole country with CUs sited in just eight locations.

Split 2 is a “high layer” split design that puts much more of the radio processing in the small cell itself – siting the MAC and lower and upper PHY in the RU-DU. That means the midhaul connection between the CU and the DU is not as latency or bandwidth intensive as other splits. BT Wholesale’s idea was to use the vCU as a multi-tenant platform for operators, with the capacity to support multiple operators over the same midhaul link, connecting to multi-band small cells. 

A different option for small cells is the Split 6, as defined within its Network FAPI specification by Small Cell Forum. Split 6 puts the functionality split lower down between the MAC and the Upper and Lower PHY – separating the RU and DU and creating a “three box solutions”. 

Generally speaking, the lower the split in radio terms (confusingly, the higher in option number), the better your fronthaul connection needs to be as you are taking more processing back in the network to an aggregation point. Split 7.2x, as most widely adopted in Open RAN to date, is a lower layer split than 6, dividing functionality between the upper and lower PHY to leave only the lower PHY on the RU.