Stand on a platform at Berlin's Hauptbahnhof, London's Waterloo or New York's Penn Station and there will be hundreds of business people touting the latest smartphones and checking their emails.

In every airport business lounge almost everyone seems to be putting the finishing touches to a presentation on an iPad (or other tablet device), or watching a movie or TV show.

Field service engineers and breakdown mechanics come equipped with data-connected laptops, so they can download the latest technical documents in moments, or check the availability of spare parts.

This is the vision of the always-connected world - and one that is promoted heavily by mobile phone companies.

It is 10 years since the world's first commercial third-generation, or 3G, mobile phone network was switched on by Korea's SK Telecom and in that time, the landscape of telecoms and the internet has changed beyond all recognition. The first 3G phones were just that: phones, first and foremost, with email and a rudimentary web browser. Promised features that would draw heavily on the speed of the new networks, such as video calling, have never really caught on.

Behind the scenes, however, engineers and product designers were working on new gadgets that would exploit the power of the new networks in ways that even the operators never thought possible.

First came the 3G data dongles, quickly adopted by corporate 'road warriors' so they could use their laptops without hunting for a wireless hotspot. These were followed by Apple's iPhone and competition from the likes of BlackBerry, Samsung and Nokia. Then, two years ago, Apple launched the iPad. Designed to work on both Wi-Fi in the office and 3G mobile networks on the road, the iPad was the travelling executive's dream.

But it was a dream that quickly turned into the mobile operators' nightmare. Unfortunately for them - and the businesses that rely on them - the popularity of tablets and smartphones has a hidden cost: network congestion. With each generation of device more powerful than the last, subscribers seem to be reading more emails, downloading more music, browsing more web pages and watching more video content.

And when too many smartphone users try to go online at once, it causes network meltdown, with users experiencing the data equivalent of a busy tone. Videos jitter or shudder to a halt, music and game downloads stop, maps and GPS navigation fail to update as you move. Email slows to a trickle, and in the worst-affected areas - such as New York and San Francisco in late 2009 - even phone calls and texts can fail to come through. Most cities have experienced at least occasional mobile 'data crunches' since.

The problem is that smartphones and tablets are almost too popular for their own good. According to the GSM Association, a trade body for mobile communications, 648 million people are using mobile broadband worldwide.

Out of a worldwide mobile phone subscriber base of five billion, that might not seem much. But those smartphone consume far more data than subscribers with more modest handsets. Almost every network that has launched Apple's iPhone, for example, reports that it has quickly become their largest data hog.

"There are issues with the structure of networks, not just radio spectrum, but how you build the network out," says Phil White, a mobile communications specialist at PA Consulting. "There is the level of investment [the networks] are putting in, and the impact of smartphones. And if you look at what's happening with cloud computing, that will take mobile data demand a step beyond where it is today."

Over the past decade, demand for mobile data in mature markets such as North America, Europe, and Japan has followed the classic 'hockey stick' curve upwards. The first 3G devices had few unique features, and only real technology enthusiasts or the very wealthy bought them. Even as 3G coverage improved, only a minority of subscribers bothered with - usually expensive - data service plans.

Gradually smartphones improved, manufacturers started to bring out 3G dongles for laptop users, and networks began to offer subscription plans with data services included, or offered for a small additional monthly fee. Mobile web browsers improved, companies started to design websites that worked on small screens, and social networks - especially Facebook and Twitter - became hugely popular.

By the time the iPad launched, demand for mobile data was already outstripping supply.

In March 2010, the average smartphone user downloaded 150 megabytes of data each month: perhaps as few as 15 to 20 web pages, or just half a dozen PowerPoint presentations. By 2015, that figure will be 1,000 megabytes (1GB), according to research by Arthur D Little and Exane BNP Paribas. Mobile broadband users - using 3G dongles or laptops - will use 5GB of data a month. Overall, worldwide mobile data use in 2015 is expected to be 32 times as high as in 2009.

Based on the operators' current capital-investment levels, their networks might not be able to keep up. In the US, AT&T reportedly increased its investment programme by 30% in 2010 to handle demand generated by the iPhone.

But Apple's devices are not the only culprits: phones based on Google's Android operating system now account for more than half of all smartphone sales, according to the technology research firm Gartner. And Android users are at least as likely to be heavy users of mobile data as Apple's fans.

As things stand, there seems to be no end in sight to the growth in demand. Despite scare stories about mobile subscribers running up bills in the hundreds or even thousands of euros for downloading movies and games, the problem for networks stems as much from the growth in smartphone and tablet users as from the amount of data that each user downloads.

Deterred by those heavy charges for 'out of bundle' megabytes, most subscribers do manage to stay within their bundled data allowances. But by doing so, in some ways they make the problem worse for the networks. A large number of users downloading 500 megabytes a month - the typical data bundle in Europe - puts as much stress on the operator's systems as a smaller number of very heavy data users.

Unlike the heavy downloaders, these regular users may be paying just a few dollars or euros, or even nothing at all, for their data. And stiff competition between networks, especially in markets such as North America and Western Europe, makes it hard for operators to downgrade their data bundles or to charge more for them.

The concentration of smartphone users in cities puts further strains on networks. Even if they invest more in hardware, they may not solve the problem. One of the greatest constraints on mobile data capacity is the available radio spectrum. That, in turn, is governed by the laws of physics. In some cities, radio-spectrum congestion is so bad that not just data but voice calls and text messages are affected, especially during the rush hour.

Mobile internet users today are downloading three times as much data as travelled across the entire internet in the year 2000, according to David Cleevely, chairman of Cambridge Wireless, a UK-based industry forum. "Mobile traffic is growing at a phenomenal rate, and as fast as anything we've seen before," he says. "Operators are jostling for position to maintain their market share. And everyone is growing used to using Skype, or video, or email on the move. Once that takes hold, there's no stopping it."

One solution for mobile operators is to buy more radio spectrum. But additional spectrum is not available in all markets and, as Cleevely warns, at best it will buy the networks 12-18 months' breathing space, if usage continues to grow at today's rate. This is without additional demands on the system from one-off events. Already, concerns have been raised over whether the UK's mobile networks will be able to cope with the additional traffic that this year's London Olympics are expected to generate.

"The amount of traffic is now hundreds of times more than in the late 1990s, when the spectrum was doled out," says Cleevely. A shortage of spectrum will force operators to continue to invest more money, by packing more mobile cells into busy areas, or to look at alternatives such as 'offloading' data traffic to alternative networks, especially Wi-Fi. With 70% of all data traffic coming from users who are at home or in the office, this could be a quick and relatively cheap way to boost network capacity.

This, though, does little to help businesses that have invested heavily in mobile technology over the past few years, and who depend on strong data signals on the road. Mobile working brings both gains in productivity and an improved work-life balance for staff, but it is far from cheap.

Even a relatively modest deployment of 500 iPads can cost €500,000 or more, once companies allow for the cost of updating back-office and other IT systems. And businesses may not want to rely on networks being able to persuade their subscribers who are indoors to connect to Wi-Fi, in order to free up capacity for people using smart devices on the move.

Already, companies developing software for mobile devices are having to rewrite their software to allow for less reliable networks, or advise customers to change the devices they use. "We are already seeing problems with accountants, who are using personal digital assistants," says Colin Gallick, CEO of UK-based software company Invu. "They are moving to iPads, which have more memory, and so more data integrity." The iPad can store more data before it needs to upload it, which can be a lifesaver when the mobile networks are congested, he points out.

And the move towards cloud computing, where companies store their data on remote servers accessed over the internet, is making the situation worse, not better. This is forcing both companies developing remote-working technologies, and the businesses that use it, to plan around using either Wi-Fi or slower but more reliable 2G technologies. "We have to assume the worst, but hope for the best," says Gallick.

In the short term, wireless-industry experts expect the problems with mobile networks - and for the companies that use them - to increase. "The operators are in a capacity crunch right now," warns Ronny Haraldsvik, senior vice president at BelAir Networks, a Canadian provider of wireless technology. "Where there is good coverage, people consume huge amounts of data."

The mobile networks themselves are putting their bets on new technology to help them meet demand. So-called 'fourth generation' networks are already being built to supplement 3G. The US is increasingly well covered, with all the main operators there offering 4G in the majority of medium-sized cities, and there is 4G in Japan, South Korea, Australia and Hong Kong. In Europe, Scandinavia and Germany have 4G, but France, Spain, Italy and the UK are further behind.

Operators, for their part, argue that they have to contend with an inconsistent regulatory framework, as well as a tighter market for investment capital. Regulators in the UK recently delayed that country's 4G spectrum auction, and in Germany, the rules are set to encourage operators to cover medium-sized towns ahead of the larger cities.

Despite this, the industry argues that it continues to invest - and that any capacity problems will be temporary.

"The industry is investing $100bn in capital expenditure between now and 2015 in mobile broadband, to bring download speeds of up to 100 megabits per second,"says Dan Warren, the GSM Association's director of technology.

"We did have people complaining they were unable to connect their iPhones in central London, but operators were stung by those stories to invest, and have done so very, very successfully. A couple of years ago, I would have agreed that operators were caught on the hop. But especially in the mature markets, they have had two to three years to address that."

Given all that, the question for delegates attending the Mobile World Congress in Barcelona this February will be whether they have done enough to put the industry back on track.

It will be a year or two still before improved networks, and especially 4G networks, come on stream in enough places to make a difference. What no one can predict is how much data 2014's gadgets of choice will swallow up.

BEYOND THE NETWORK
Hot topics at February's Mobile World Congress in Barcelona

The Mobile World Congress is where designers, network operators, software developers and businesses meet to shape the industry's future. As well as users' insatiable demand for data, here are some hot topics for Barcelona's tapas bars.

Mobile security Security watchers have claimed for at least a decade that a major virus threat to mobile phones is just around the corner. But concerns are growing that, with more powerful devices such as the iPhone, iPad and Android handsets, virus and malware writers will turn to them in earnest.

One reason is that there are fewer mobile operating systems to target. Ten years ago, most manufacturers of handsets developed their own software. Now, smartphones run Android, Apple's iOS, Microsoft's Windows Phone or the BlackBerry OS. Sheer weight of numbers makes iOS and Android the most attractive to hackers.

Another reason is the growth of app stores, which malware writers can use to distribute viruses or other fraudulent software. One software writer proved in 2011 that he could bypass Apple's App Store security tests, although his application was quickly removed by Apple. As business users store more valuable data on handsets, they will become more attractive as a target.

Small cells Small-cell technology helps mobile operators improve coverage by putting in large numbers of low-powered transmitters, or femtocells. These will be sold, or even given away, to consumers and businesses, which will then plug them into their broadband networks. Larger picocells are being installed in shopping centres and busy outdoor areas to boost signals there. The advantage of small cells is that they improve in-building coverage and, unlike Wi-Fi hotspots, do not need phone subscribers to log into them. The challenge remains convincing users to hook up small cells to their private networks.

Mobile health
Mobile health, or m health, is one area of technology where relatively small investments promise significant returns.

In most healthcare systems, drugs and wages are the largest costs. Mobile health systems can reduce both demand for drugs, by helping with preventative care, and drugs wastage. And by linking health monitors to the mobile network, doctors and nurses can visit patients less often, and patients can make fewer journeys to clinics or hospitals for routine checks.

Mobile health monitors work either by connecting to the patient's own smartphone, or directly to the mobile network. This does require an upfront investment. But the UK's NHS - and other healthcare systems - have found that simple steps, such as reminding patients about appointments via a text message, can also bring significant cost savings.