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7 September 2021

Mavenir adds 2G to Open RAN but 3G is delaying Vodafone UK’s efforts

By Wireless Watch Staff

Some of the doubts about Open RAN as a technology that will be deployable in the short term for large-scale networks relate to advanced use cases. Brian Daly, head of core network and regulatory standards at AT&T, told the recent Big 5G Event that Open RAN would be introduced only gradually because “more work needs to be done to ensure O-RAN can meet our complex feature set”. “You don’t just go ‘full open’,” he said, though AT&T intends to introduce the technology in some rural roll-outs later this year or in early 2022.

However, even in those relatively undemanding rural networks, operators meet a different challenge with Open RAN – not its support for very advanced implementations, but for legacy 2G and 3G networks. The UK’s BT has already been vocal about the difficulty of introducing new vendors that do not have support for legacy networks, especially 2G, which the operator plans to retain for at least a decade – this even formed part of CTO Howard Watson’s testimony to a UK parliamentary hearing about alternative vendors for 5G.

Watson said: “The key point is the Single RAN concept and the 2G and 3G legacy. Right now, 50% of my voice calls still use the 2G and 3G network … My view right now is that for a replacement technology today, 2G has to be a critical part of the solution.”

Now another UK operator, Vodafone, has turned the spotlight on 3G, acknowledging that it cannot rely heavily on Open RAN in its main network until it can turn off 3G. Vodafone UK plans to build an Open RAN to cover about 2,500 sites, initially mainly rural – some new and some to replace Huawei gear. It has named most of its suppliers, with a leading role for Samsung, along with NEC, Dell, Wind River, Keysight and Capgemini.

But Ker Anderson, head of radio and performance at the operator, told a recent round table discussion in London that the continuing presence of 3G is “holding us back from introducing Open RAN”. He added: “Part of the challenge is that Open RAN is not geared up to 3G. Do I leave part of the Huawei kit running 3G and put in Open RAN serving 2G, 4G and 5G and then create a dog’s dinner of capabilities so that managing traffic … becomes a performance nightmare?” And running two networks in parallel incurs significant extra costs in terms of tower space, energy and so on.

This will be a relatively short term problem since Vodafone has already refarmed its main 3G spectrum band, 2.1 GHz, for 4G and is starting the process of reducing the amount of 900 MHz spectrum assigned to 3G, as traffic levels on the legacy network drop. But Vodafone retains a 3G base that has no interest in moving to 4G, and it will take a few more years, at least, to switch off 3G altogether. Clearly in many emerging markets, where operators want to introduce Open RAN to reduce the cost of 4G or 5G roll-out in certain areas, the timescale to turn off legacy networks will be even longer.

The vendors are rushing to address the problem, but have focused more efforts on 2G than 3G in Europe, since most operators will keep the older technology for far longer than 3G to provide voice, ultra-rural and machine-to-machine coverage. Although BT’s Watson highlighted Samsung’s lack of 2G support in his testimony to the parliamentary committee, Samsung is supporting 2G as part of its Open RAN contract with Vodafone.

Parallel Wireless does have 2G and 3G support under its ‘All G’ platform and Mavenir gained 2G technology when it acquired UK small cell vendor IP.access last year.

Indeed, Mavenir announced commercial readiness of its containerized 2G architecture, based on the IP.access intellectual property, last week. This supports an enhanced 2G interface protocol – Multi Radio Access Technology (MRAT) – on top of the O-RAN enhanced eCPRI fronthaul interface. The company said it would submit its design to the O-RAN Alliance for inclusion in its framework. Other features include frequency hopping, multiple codecs, ciphering and handovers, said the company.

Mavenir has containerized the GSM Layer 1, 2 and 3 protocols within 2G into the Open RAN distributed unit (O-DU) microservices architecture, supporting a lower layer DU split that enables operators to centralize 2G DUs. These can be run in parallel with 4G/5G and on the same platforms.