Telcos in Europe and some other markets outside China remain worried that a government ban on using Huawei in 5G networks would cost them hundreds of millions of dollars. The rationale is largely that Huawei’s 4G radio equipment would be incompatible with 5G gear from the new vendor, and therefore need replacing at great expense. For Vodafone UK, that would mean ripping out about 6,000 Huawei basestations.
But Finland’s Nokia has now come forward with a proposal it says would tackle the problem head on, allowing an operator to keep its Huawei 4G kit as it introduces 5G equipment from another vendor. Sweden’s Ericsson, Huawei’s other big European rival, is promoting a similar workaround.
It is not just about facilitating a Huawei replacement, and the European vendors are certainly not pitching it that way. Their solution takes aim at one of the big interoperability problems that plagues companies deploying next-generation mobile networks. Unless that is fixed, an operator may have to use the same 5G vendor that built its 4G network — even if it prefers another’s 5G radio technology.
At issue is the X2 interface, which today supports handover between basestations in 4G networks. When 5G services are launched, X2 should ideally allow 4G radio systems to communicate with 5G technology so that operators get peak performance on their networks. Unfortunately, though, X2 has not measured up well on interoperability. “Each vendor tends to implement it slightly differently to get superior performance on their own systems,” says Marcus Weldon, Nokia’s chief technology officer.
As a result, any operator that wants to get the most out of its 4G and future 5G networks has been faced with two choices: Stick with its current vendor, which will obviously support interoperability between 4G and 5G in its own products; or switch suppliers and rip out the old one’s 4G systems. Service providers that want to change vendor, but avoid any costly swap-out, have been in a bind.
Until now, perhaps. Thanks to a new feature called dynamic spectrum sharing (DSS), which is only just becoming available in radios, operators may be able to introduce a new 5G vendor without having to bid an expensive farewell to the existing 4G supplier.
As the name implies, DSS allows an operator to move spectrum between different radio technologies as and when needed. It’s a feature that all operators seem likely to need as they grapple with emerging bandwidth demands. But introducing it now would also provide an interoperability fix, says Weldon. An operator would buy DSS radio equipment from its new 5G vendor and initially run that in 4G mode, using some existing 4G spectrum. This “overlay” service would ensure there is interoperability between the 4G and 5G systems. And roaming between different vendors’ 4G networks would happen at the packet core level, as it always has, according to Weldon.
Ericsson agrees DSS is an answer to the interoperability problem. “We don’t think X2 is the way forward because it would slow things down and be expensive,” says Thomas Noren, Ericsson’s head of 5G commercialization. “This [DSS] is a much better way forward.” The ability to reallocate spectrum every millisecond is a massive industry breakthrough, he insists. “It means you can be totally flexible between 4G and 5G and allow any mix of the two to run in a band.”
