The 2G/3G design review your IoT solution needs right now

On paper, your IoT solution may look resilient. It ships with a multi-network SIM, supports LTE, maybe even 5G.

But in practice, resilience depends on how devices behave when coverage dips.

And right now, if your devices ever rely on O2’s 2G/3G networks for fallback, it’s a present-tense design flaw — one that could expose your customers, your brand, and your margins if you don’t catch it now.

The 2G/3G story everyone’s missing

Virgin Media O2 is withdrawing inbound roaming on its legacy networks: 2G from 1 October 2025, and 3G by 31 December 2025.

This isn’t entirely the familiar “2G/3G switch-off” story about an operator shutting down its service.

It’s more about SIMs from other operators — especially multi-network SIMs — losing the ability to fall back to O2’s 2G and 3G.

So far, many organisations have migrated to 4G/5G or LPWAN alternatives. But O2 say they’re still seeing significant inbound traffic on those 2G/3G legacy networks.

That means plenty of IoT devices are still leaning on those paths today.

Here’s what that risk looks like:

• Hidden exposure: Devices that roam or fall back via O2 2G/3G are on a ticking clock. Just because they worked last week doesn’t mean they’ll work in October.
• Unexpected failure modes: Even “4G-rated” devices can default to 3G or 2G thanks to firmware quirks, module limitations, or marginal coverage.
• Silent impact: Because inbound roamers aren’t O2’s direct customers, O2 can’t always identify who’s exposed. Many organisations may not even know their devices are at risk.
• Regulatory implications: Critical services like telecare, alarms, and monitoring depend on always-on connectivity. Failures post-switch-off could carry legal, financial, and reputational fallout.

For IoT solution companies, the risk multiplies:

At scale:
A firmware quirk rolled across hundreds of devices can trigger mass outages.

At renewal:
Customers don’t renew with providers whose solutions “just stop working.”

At reputation:
Reliability is as much part of your product as the device itself. Fail on that, and you’re not just swapping SIMs — you’re losing trust.

Four areas every provider must review now

1. Map reality, not assumptions

Check the actual device firmware and hardware. Don’t assume a “4G-capable” device is always staying on 4G.

• Audit hardware: does the module support the right 4G/5G bands in the UK? (Many early IoT modules only support limited bands, or exclude Cat-1 bis.)
• Audit firmware: is it updated so the device prefers LTE over GSM when both are available? Older firmware often defaults to 2G first.
• Audit usage: What does the device actually do in the field? Run reports to see which endpoints are still roaming back to 2G/3G. That’s your hidden risk list.

2. Prove roaming behaviour in the field

Lab testing isn’t enough. You need to simulate what really happens under network stress when O2 2G/3G disappears:

• Force devices to camp where O2’s 2G/3G would normally be used, then block those networks.
• Confirm the device cleanly re-attaches to 4G on another UK network, without hanging or retry loops.
• Capture logs so you can show customers evidence that their devices won’t go dark when the switch-off hits if needed.

3. Migrate with intent

Don’t patch the problem by moving devices onto “another 2G” network — that’s just kicking the can. Instead:

• Standardise on Cat-1 / Cat-1 bis modules (low-power, wide coverage, and roaming-ready).
• Where devices need mobility or higher throughput, spec Cat-4/6 LTE or above.
• Always pair with multi-network SIMs so the estate has redundancy if one operator has local coverage gaps.

4. Ship reliability as part of your offer

Reliability should be baked into your solution, not treated as an afterthought.

• Add estate-level health monitoring so you see outages before customers do.
• Enable usage alerts and thresholds to catch anomalies (e.g. a device suddenly drawing 5x data).
• Provide customers with regular reports on uptime, failover events, estate health as a service.

The bottom line

If it sounds like a lot of work, remember: a migration done right is an upgrade to your solution design and a chance to strengthen your offering.

And if you act now, you gain:

• Fewer emergency truck rolls: fixing fallback issues under pressure is costlier.
• Better reliability reputation: customers value evidence, uptime, resilience.
• Competitive advantage: many providers will scramble; being ready before 1 October will let you take the high ground.

Swapping a SIM is the easy part.

Proving resilience and redesigning for the long term is where providers win and avoid painful churn.