AT&T told the US regulator, the FCC, that it plans to add Open RAN-compliant equipment to its network “within the next year”, a similar timeframe to that of Verizon. But it says there is significant work to do to “ensure that O-RAN can meet our complex feature set”, especially for high end enterprise applications and the FirstNet public safety system.
AT&T – together with China Mobile – contributed much of the initial code for the O-RAN Alliance’s specifications, when that body was formed from the merger of the AT&T-founded xRAN Consortium, and the China-centric Cloud-RAN Alliance. However, it has been less active in Open RAN trials and roll-outs than operators in Japan and Europe, so far, and may be planning a more customized, internally driven multivendor platform.
Verizon has already provided some indications of its Open RAN roadmap, with plans to start procuring compliant equipment by the end of 2021 – although it was clear that, at least initially, this would come from its existing RAN vendors, Ericsson, Nokia and Samsung. In other words, Verizon is mainly planning to insist that certain O-RAN specs – probably starting with the open fronthaul interface – are enabled in new equipment from its suppliers, rather than shaking up the chain as yet. It has, however, said it aims to introduce additional partners in future waves of 5G RAN.
The large operators are keen to shake up their supply chains, but wary of any trade-offs in terms of network performance, just when they are rolling out 5G Standalone and looking for new levels of reliability and data speeds. AT&T wrote in an FCC filing: “The challenge for an operator shifting to any open network architecture, including but not limited to O-RAN, will be maintaining network reliability, integrity and performance for customers during the transition … As we introduce O-RAN into our network, our goal will be maintaining the same high level of performance at scale. We are actively working in this direction.”
It said that most operators will phase in O-RAN gradually, adding: “While the industry will likely experience a gradual introduction of O-RAN into existing networks, those developments are not mutually exclusive. Some deployments may still leverage traditional network infrastructure. For example, many 5G RAN deployments will be specific to the site environment or the particular needs of a customer.” That reinforced the assumption that most non-greenfield large operators will experiment with O-RAN first in enterprise or small cell scenarios before introducing the new architecture to the primary macro network.
AT&T has implemented a localized Open RAN network in Dallas with equipment from Samsung and Ericsson (though the latter does not provide commercial products that support O-RAN specs, so this was presumably a custom project). It has also co-developed and trialled a RAN Intelligent Controller with Nokia, based on O-RAN RIC specs.
The US operator has a particular challenge when it comes to ensuring network reliability because it is building out the FirstNet public safety network, as well as aiming to support very high performance, mission-critical capabilities for enterprise and industrial customers. It continued in the filing: “AT&T’s diverse customer base includes individuals, small businesses, government agencies, including FirstNet, and large enterprise clients, many of which require an extremely complex feature set. AT&T will not introduce new technology that cannot or will not fulfill all of those requirements at scale. More work needs to be done to ensure that O-RAN can meet our complex feature set. AT&T is working with several partners on addressing these issues and fully anticipates resolution over time.”