Apple is unlikely to include support for voice calls over 4G LTE networks among the new features packed into its newest iPhone.

That's the view from several analysts ahead of Apple's event this Wednesday when the latest version of its iPhone is expected to be revealed.

The device is predicted to have LTE support, but it seems more likely that the smartphone will rely on 3G, rather than 4G networks, when it comes to making voice calls. A 4G voice service -- that is, Voice over LTE (VoLTE) -- relies on IP Multimedia Subsystem (IMS) in a mobile operator's core network and requires IMS support in the handset as well. (See 5 iPhone 5 Features Carriers Should Care About .)

The main reason the analysts aren't convinced that Apple will support VoLTE in this iPhone is that there just aren't that many networks that support the services in the first place. To date, it's only available from SK Telecom (Nasdaq: SKM) and LG Telecom in South Korea and MetroPCS Inc. (NYSE: PCS) in the U.S. (See South Korea Hears First 4G Voice Service, 4G Finally Gets a Voice and LG U+ Offers 4G Voice With Ericsson.)

Dean Bubley, founder of consulting firm Disruptive Analysis Ltd. , says he's almost certain that the new iPhone won't support VoLTE.

"I can't see Apple putting native support for IMS-based services into the iPhone -- they would lose hard-won control," he says. "At some point we might get some sort of bridging function via iCloud or WebRTC, but I highly doubt they'd support IMS-down-to-the-device.

"Given that AT&T & Verizon Wireless are unlikely to roll out VoLTE for another year in any meaningful way, and most European operators will be at least a year -- maybe 2 years -- away too, I can’t see it happening."

Heavy Reading Senior Analyst Gabriel Brown adds: "I’m not sure there’s much point in speculating before the launch -- we'll know for sure later today. But assuming the new iPhone has LTE, it is likely that it will use the 2G/3G circuit switch network for voice. Then again perhaps Apple will surprise the market and go for VoLTE?

“We know VoLTE works, so it’s a question of timing more than anything," says Brown. "In Light Reading's 2012 Mobile Packet Core Benchmark Survey, only 7 percent of operator professionals said they had no plans for VoLTE, whereas 26 percent said they would offer VoLTE as soon as possible, and 44 percent within two years of the launch of LTE.”

Bengt Nordstrom, founder of Northstream consulting firm, also isn't expecting to see VoLTE in the next iPhone.

"There are plenty of LTE devices -- all are circuit-switch fallback based [for voice]," he says. "VoLTE is only meaningful when there are other VoLTE devices in the market and the networks are interoperable."

— Michelle Donegan, European Editor, Light Reading Mobile