As my telco contacts digested MWC, they offered an interesting consensus comment; 55 of 75 who commented on the show made this remark: “Open RAN can’t fix 5G/6G” which I think is an interesting comment on both. One that, obviously, begs the “Why?” question.
It’s clear to almost every telco that we’re evolving to a more “converged” view of broadband, one that is based on common infrastructure for fixed, mobile, satellite, and even WiFi. The clarity is spoiled by the fact that while that seems obvious at this point, and should have been a fundamental point in the design of 5G/6G architecture, that really didn’t happen for 5G and isn’t really doing that for 6G either.
“If you accept broadband convergence, the primary goal has to be reuse of infrastructure elements across every type of access. We don’t have that,” one telco noted. The big offender, they say, is mobile, but there’s also a need for what another telco called “the Grand Unifier”.
If you look at the architecture of 5G, you can argue that it really defines three things—the RAN, mobility management, and the core. Most of the telcos think that the “core” piece should not exist as a part of mobile infrastructure at all, but rather be a single common central element to broadband. Access features can map to core features, but they should never extend into the core. That’s an essential stating point, telcos think, but not the whole story.
Mobility management, if you cut to the chase, has two main elements—registration of devices and “finding” the access point for those devices as they move about. The function should be a boundary function at the point of connection to the service core, perhaps some metro-level point, where a “service address” that’s known to the service network, say the Internet” is mapped onto a tunnel that gets the packets to the right access point. Today, that’s mobile only, but many telcos think that it should be a universal feature, one that lets devices roam to any cell, any wireline broadband connection (through WiFi to a device) and satellite. This is a goal, most agree, of 6G, but the implementation may be an issue. What a select group of thoughtful telcos want is for this to be done by creating a different relationship between the control and user planes.
Does this sound like vRAN? Not according to the commenting telcos. According to them, vRAN is about turning functions into software, and of course it’s about the RAN. Telcos say that you have to start with the whole mobility management issue if you’re really going to optimize infrastructure for a converged future. That means taking all the user-plane functions and incorporating them in the router. If you’re going to create tunnels and steer/route onto and off the tunnels, you do that in the routers, so that all the data handling for all access options is built into devices that are already handling “traffic”. You then create an interface between the routers and the mobility control-plane features so that mobility management can create tunnels, direct traffic, and break them down. MPLS, they note, already does tunneling in routers, and many think that MPLS should be the mechanism of choice here.
Once you have the data plane centered in traditional routers, you can host the control-plane functions as software features on utility servers. This makes mobility management a true overlay element, and also enables it to direct service traffic to any access technology. However, there still might have to be some extra handling issues to face there, given that every access network assigns a device to an address. How do you manage directing a service address to an access address. One telco suggestion was to treat an entire access network as a private address space and push and pop address headers at the boundary. This could be a function of a router if the router could pull address translation from a database, somewhat like SDN switches would pull routing information, caching it for the duration of its need. The access networks would presumably manage this at the boundary.
What about the “open” part, like Open RAN? The rule, the telcos say, remains that control and data plane separation, with the former in software and the latter inside routers, would be paramount in designing the mechanisms for access, whatever they are. Thus, they’d want an initiative to open the RAN to continue the separation of control and data, and to use routers/switches for the latter. As far as the former, there is some interest in having all control-plane functions be software, but a recognition that as you get closer to the antenna, the value of not only openness but even of control/data separation reduces.
This attitude arises from two factors. First, the major telcos don’t want to integrate multiple vendors. Second, they don’t think that openness begats innovation in the RAN, because only the giants can really afford to innovate. “The concept of ‘open’ is just like any other tech feature, meaning it has to pay back overall,” one commented. “The media loves an open RAN,” said another, “but for us, not so much.” Most admit that the whole concept of openness ends up being justified as a way to hammer down prices, and a defense against a vendor leaving the market. Those justifications increasingly don’t work.
What appears to be true, surely for those telcos who offered me comment and likely for others, is that neither Open RAN nor vRAN is seen by telcos as a broad solution to their business challenges. Some see a path to creating an infrastructure model and service model in a 6G-ish sort of way, but with specific technology elements so far absent from, or even contradicted in, 6G standards. Others are simply trying to navigate the demand forces that drive a need for greater capacity, the lack of differentiated services that could command premium payment, and the growing pressure on them to constrain costs to stabilize their business model.
