Telstra got out ahead of its customers last week by announcing it would switch off its 3G network in June 2024.

Like other telcos, it has learnt that, as in any breakup, exiting a network requires honest communication and a good sense of timing.

Back in 1999, more than a few Australian farmers couldn't be persuaded to let go of their beloved AMPS network, believing the old analog service covered the vast interior better than GSM.

Telstra replaced it with its unique CDMA 850MHz service, which in turn broke hearts in 2006 when it was switched off because it largely duplicated the W-CDMA network.

The latest closure, making way for 5G, is unlikely to prompt too many tears, with the network accounting for just 6% of traffic.

But it's a reminder that today, 18 years after the first UMTS network was deployed, we are well into the sunset phase of 3G.

Japan hasn't had a 3G network since 2012, Verizon is shutting off both 2G and 3G at year-end, while AT&T and Sprint are set to switch off in 2022.

Many more 2G than 3G networks have been shuttered, of course, but it is surprising to learn that quite a few operators have no plans yet to terminate their GSM deployments.

This is especially true in Europe, where Vodafone expects to terminate 3G in the next two years but hasn't set a timetable for 2G. Nor have Deutsche Telekom and Telefónica.

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The problem is especially acute in China.

Around 8% of mobile users are using 3G, according to MIIT stats from May. But nearly twice as many, or 238 million, mostly in rural areas, have GSM-only subscriptions.

The aggregate number is declining -- down 20 million in three months -- but in some regions it is either static or growing. Sichuan province actually added 1.96 million 2G users in three months; nearly a quarter of its mobile subscribers are on 2G.

Across the country, customers bought 8 million 2G phones in the first five months of the year.

One problem here is clearly economic. Some rural low-income households can't afford 4G. Solving that will take more than a frank and honest conversation.

But the other part likely relates to coverage.

An analyst writing for the Sina website called for the accelerated rollout of 4G in rural China because right now the LTE network can't live without 2G.

While three quarters of subscribers are on LTE networks, only 53% of voice calls are VoLTE, with the remainder falling back to 2G.

That probably also accounts for the unhurried approach of the Europeans to exiting GSM.

The lesson is that while building out 5G, many operators will still have to invest to deepen their 4G networks.

Until then, they just can't quit 2G.

— Robert Clark, contributing editor, special to Light Reading