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Are the nation’s LTE wireless carriers prepared for the video chat data crunch expected to come with the next-generation iPhone and other devices that are expected to launch this fall?

the answer: it depends on whom you ask.

both AT&T and Verizon Wireless decline to say whether they are ready for the data crunch.

Over the summer, both carriers introduced data sharing plans that analysts believe were timed to help limit a surge in heavy data use expected especially with the use of Apple’s FaceTime real-time video chat software on the iPhone.

“If I were a carrier, I’d be rather frightened by FaceTime,” said Jack Gold, an analyst at J. GoldAssociates. “If everybody used FaceTime, bandwidth would go up dramatically, and the user experience would go down.”

Imposing data sharing plans with set fees for specific numbers of gigabytes a month — and penalties for exceeding the set amounts — could help top carriers AT&T and Verizon avoid data capacity overload problems on their 4G LTE, and even 3G, networks, Gold said.

“Requiring the data sharing plans is really just another way for carriers to say they are limiting your access,” he added.

AT&T has come under fire in recent days for announcing plans to require users to sign up for a Mobile Share data plan in order to conduct FaceTime video chats over its current 3G and future cellular networks.

FaceTime will be available for cellular network use, instead of just over Wi-Fi, in mobile devices running the forthcoming iOS 6, which Apple announced earlier this year.

Sprint, the nation’s number three carrier, has stood solidly behinds its unlimited data plans, and is just starting to roll out 4G LTE technology.

At an event to mark the activation of its 16th LTE location in Baltimore earlier this week, Sprint 4G engineering manager Viet Chu told reporters that “if some abuse the system [with heavy data use] we would address it.” He didn’t specify what steps the carrier may take.

Concerns about FaceTime’s impact on cellular networks are particularly acute, partly because the iPhone is the top selling smartphone model worldwide and because the next model will reportedly support LTE, which would help make the device even more popular.

the upcoming iPhone is also expected to have a larger screen — more than 4-inches compared to the current modle’s 3.5-in. screen — which would make video chats easier.

That creates problems for carriers because like most two-way chat apps, FaceTime is an enormous bandwidth hog.

Video chat often uses about 3 megabytes of data per minute, though the exact rate depends on encoded software, noted Wendy Cartee, vice president of product and technical marketing for JuniperNetworks.

Juniper develops software that carriers can use to improve bandwidth at cell tower locations. it also sells a Universal Access router that can be installed at individual cellular tower locations to help streamline the data traffic at the point where it joins the backhaul link. Backhaul is the wired (or fiber optic) segment of a network between the wireless portion received at a cell tower and the network core.

such products from Juniper and other vendors like Cisco and Alcatel Lucent should help U.S. carriers handle FaceTime, or other rich video applications on their LTE networks, Cartee said. “Carriers do plan for these types of changes in apps,” she noted. “I’m looking forward to using FaceTime over cellular.”

LTE is also inherently faster than 3G (generally LTE networks provide up to 8 Mbps on downlinks and up to 3 Mbps on uplinks) and can generally handle more capacity than earlier-generation networks, analysts noted.

Verizon offers LTE service in most of the geographic U.S. AT&T trails Verizon in coverage but has touted its GSM 3G HSPA speeds where its LTE networks aren’t ready.

Gold said data sharing pricing plans will help AT&T and Verizon deal with the data crunch as much as the new routers and other technology.

“Before these data sharing limits, there was no reason for end users to do any kind of self-regulation,” he explained. “Now if they use a lot of data, it will cost them.”

as a result, Gold said AT&T won’t get the heated criticism it got for not being able to support the original iPhone five years ago over GSM. “Data capacity will be much less of an issue with iPhone 5 than the first time around, which kicked AT&T’s butt,” Gold said.

still, AT&T has expressed concerns about FaceTime data usage, noting its worries in a blog post this week that defended forcing FaceTime users onto its Mobile Share data plans instead of using individual plans.

“We are broadening our customers’ ability to use the preloaded version of FaceTime, but limiting it in this manner to our newly developer AT&T Mobile Share data plans out of an overriding concern for the impact this expansion may have on our network and the overall customer experience,” said Bob Quinn, senior vice president for federal regulatory matters, who penned the blog post.

He added: “We will be monitoring the impact the upgrade to this popular preloaded app has on our mobile broadband network, and customers, too, will be in a learning mode as to exactly how much data FaceTime consumers on those usage based plans.”

Nav Chander, an analyst at IDC, said that AT&T’s blog post shows that the carrier is “being very, very careful” with FaceTime. “The blog tries to lower expectations, anticipating the worst case,” Chandler said.

Chander has also tracked what he called a massive improvement in backhaul capabilities by U.S. carriers in the past two years. Generally, he said carriers have expanded by 50 times the backhaul capability in their networks since the first iPhone was introduced.

in many cases in dense urban areas, a dual copper T1 connection from a cell tower to the wider network (with a 3 Mbps capability) has been replaced by a fiber optic connection with 1 Gbps capacity, he said.

Chander also noted a “huge increase” in the number of cell towers nationally in the past three years. Often, one carrier will own a tower and lease it to several other carriers to allow them to attach antennas.

While some experts feel U.S. carriers will be ready for heavy data usage over LTE, others say there’s really no way to know what will happen despite all the technical and restrictive pricing preparations.

“There’s really no way of telling if carriers are ready for an LTE iPhone,” said Seamus Hourihan senior vice president of strategy at Acme Packet. “There are many different constraints in networks and one is the area of bandwidth. But there’s no such thing as unlimited bandwidth.”

Acme provides software to carriers to improve network efficiency.

“Bandwidth in 4G LTE networks initially is not going to be a problem, but over time, if you use it for interactive video or watching moves, yeah, it’s going to be a problem,” Hourihan said.

a common complaint with FaceTime even over Wi-Fi has been video freeze-ups and dropped calls that make the experience difficult. if LTE isn’t available at the tower near a FaceTime user, 3G networks might offer a worse experience than Wi-Fi.

FaceTime connections will also depend on what spectrum band carriers use for LTE. Lower frequencies carry signals farther, just the same way that a low base guitar can be heard further away from a rock concert than a high pitched singer.

both AT&T and Verizon worked to get 700 MHz spectrum at the lower end for LTE for that reason, Gold said.

Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen, send e-mail to or subscribe to Matt’s RSS feed .

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