Network can't take it
Complicating life for the networks are people like Cherif Paul, a university student in Paris who does all his internet surfing via mobile because he doesn't have a fixed-line phone or broadband connection at home.

"I use my laptop and dongle for everything," said the 23 year-old. "It saves me money and it's more convenient when I am on the go."

Such practices make mobile operators nervous, especially when customers are on flat-rate plans.

Since 2005 the number of fixed lines globally has fallen 0.9 percent to reach 1.24 billion lines, according to IDATE, a telecom market research firm. Over the same period, the number of mobile subscribers has gone up 95 percent to 4.22 billion.

About 10 percent of mobile users -- who are often players of bandwidth-intense video games or music and movie pirates -- account for 80 percent of the data traffic, according to operators.

"The dongles cause people to use the wireless network just as they would use their fixed broadband line at home," said Accanto's Campriani. "But the network just can't take that."

Operators are trying to educate customers that mobile broadband should be the secondary method of access, not the main one. "If we don't succeed in sending this message, then we'll have to spend such a huge amount to boost the network capacity that it would be very hard to make ends meet," said Telenor's Amundsen.

In France, dongles and the expanded use of smart phones caused data traffic on SFR's mobile network to increase tenfold last year while revenues increased 30 percent, Allemand said.

SFR is a unit of Vivendi.

Solutions
Operators have already started responding to the data crush with new investments, phasing out flat-rate plans, and introducing techniques to curtail the heaviest use.

One approach some have adopted is to shift some mobile traffic over to the fixed-line network, which is more stable and can handle heavier traffic. Networks in Japan and Korea, two of the countries with the most advanced mobile broadband, are also built this way and face less severe congestion problems.

When Telstra invested $1 billion to beef up its mobile network three years ago, it used this strategy.

In France, SFR linked many of its mobile base stations with fixed fiber lines to better handle data traffic.

In addition to investing, most operators are implementing systems that slow or stop internet access once a subscriber exceeds an allotted amount of bandwidth.

"We have to do this otherwise only a few users will end up straining the whole network," said Telenor's Amundsen. To keep up with data traffic, Telenor has undertaken 800 projects in its Norwegian mobile network in the past six months, he added.

Esa Rautalinko, who heads TeliaSonera's mobile network in Finland, warned that such challenges were not going to disappear. "We are closer and closer to a situation where we reach the limits of our capacity," he said.