Vodafone Germany has identified a data handover problem that may be affecting the service continuity of some of its early LTE customers.

The operator recently launched a new USB dongle (aka "surfstick") from Huawei Technologies Co. Ltd. that supports its LTE as well as its 3G networks, but there's a hitch in the data services when users move from one network to another that the operator is working to resolve.

A Vodafone spokesman in Germany explained the situation in an emailed response to Light Reading Mobile: "To switch between the GSM/UMTS network and the new LTE network you have to disconnect the LTE surfstick from your PC or laptop and plug it in again. A new Internet connection will then be established."

That sounds awkward, to say the least.

The spokesman also said the operator was already working on a solution and that this would be resolved "very soon," but he did not specify a timeline for a fix.

This 3G/LTE handover issue is not likely to affect many Vodafone customers yet, given that the operator only launched the device last month and that most of its now 80,000 LTE customers subscribe to a fixed, DSL-replacement-type service in underserved broadband areas in the country. Also, the nature of USB stick mobile broadband usage is more portable than mobile, so the demand may not be so great to maintain a good data connection while on the move.

Indeed, a trawl through translated German user forums did not reveal any disgruntlement about this issue. [Ed note: I really need to get out more!]

But Vodafone's handover problem between 3G and LTE does highlight the difficulty of integrating a new evolved packet core (EPC) with the existing, legacy network. And that has implications for operators as they offer their customers LTE smartphones that will require mobility and a good handover to and from the 3G network.

"Operators have consistently identified integration and handover with the 2G/3G packet-switched core as the biggest challenge they have when rolling out EPC," says Gabriel Brown, senior analyst at Heavy Reading .

There are a few unanswered questions about Vodafone's situation too. Where does the problem lie for such an awkward handover between 3G and LTE networks -- in the radio access, core, or device, or across all of them? And does this happen only when moving from 3G to LTE, or also from LTE to 3G?

What's certain is that having to unplug a USB stick to reestablish a data connection cannot be a good user experience.

Vodafone launched LTE services in Germany in November 2010. Here's more on what it's been up to there:

— Michelle Donegan, European Editor, Light Reading Mobile