Seoul's operators set up voice calls over 4G in a median of 1.06 seconds — faster than any 5G VoNR deployment that Ookla measured across eight cities worldwide. The figure comes from Ookla's RootMetrics testing in London, New York, Seoul and Singapore, among other cities, and it frames an uncomfortable reality for the industry: most voice calls, even in markets with live 5G cores, still ride on LTE.

Ookla calls VoLTE the "gold standard" for consistency and speed in call setup. In Seoul, 90% of VoLTE calls connected in under two seconds, the threshold at which a call feels "instant" to the user.

Why does 4G still win on voice?

The answer is largely time. 4G voice has had a decade of refinement, while 5G standalone (SA) core rollouts remain slow, so carriers in most markets fall back to LTE for calls.

"The vast majority of standard voice calls in developed markets are still going over VoLTE. Even in those markets that have been very proactive on rolling out 5G standalone, in many cases they are still dropping the call back to LTE and not using the full 5G core," said Luke Kehoe, lead analyst at Ookla. "Many operators have tested VoNR over NR and found the performance initially to be subpar relative to VoLTE."

The picture is not uniform. Six of the eight carriers Ookla tested connected calls faster on VoNR than VoLTE. Singapore's Singtel and Malaysia's Yes both clocked faster setup times on their 5G voice deployments than on their own 4G networks. But the laggards show how wide the gap remains: Singapore's StarHub saw VoNR setup times 32% slower than VoLTE, and Korea's KT was 13% slower.

That divergence points to optimization maturity rather than any inherent limit of the 5G voice standard (VoNR). Kehoe likens it to the transition to 4G, which had its own voice teething troubles.

"It really is down to the need for more optimization. You're moving to a whole new technology stack ... with a new voice standard, while moving away from something that has been refined and optimized over a decade. That's really the chasm," he said.

Does call setup time actually matter?

It does, because it is one of the few network parameters users directly notice. Push the call button and wait much longer than two seconds for a ringtone, and users drift toward alternatives like FaceTime or WhatsApp — more often than they already do.

The stakes are real even as voice volumes shrink. UK regulator Ofcom reported that mobile-originated voice call minutes fell 4.6% year on year to 36.84 billion in the first quarter, with calls to landlines down 7.2%. Yet Ookla notes that a persistently poor voice experience drives churn and customer complaints, which makes the basics commercially critical.

"Voice is very seldom spoken about in the industry. From an operator perspective, it is absolutely critical that something as basic as this just works. … Getting the calling experience right is really important," Kehoe said.

How soon will 5G voice catch up?

Probably faster than the 4G transition did, according to Ookla. Where operators have already optimized their 5G cores for voice — KT, Singtel and Yes are the cited examples — connection times are competitive with 4G.

"They are getting close to being competitive with the best VoLTE networks already," said Kehoe.

Looking ahead, Ookla expects 5G voice to surpass 4G on quality and richer calling features as SA deployments mature, and it plans to extend its testing beyond setup time to parameters such as dropped calls — a benchmark that will show whether the VoNR gap closes as quickly as the early optimizers suggest.