LTE (Long Term Evolution) has picked up steam in the last few weeks, with operators moving forward and auctions taking place, helping the technology become a global standard.

On Wednesday, U.S. operator Clearwire formalized its plans for an LTE network, which it will build if it can get the financing sorted out. AT&T is also getting ready to launch its LTE network in the US, and recently said its first LTE USB modem is "coming soon."

LTE is also picking up momentum in other parts of the world. In Europe, LTE Networks have been launched in Norway, Sweden, Poland, Austria, Finland, Germany, Denmark, Estonia and Lithuania. In addition, more European countries are organizing auctions that will allow operators to buy the spectrum needed to launch LTE services. Spain recently announced the results of its second LTE auction, and in Italy and France auctions for networks based on the technology are also under way.

Increasing operator interest in building LTE networks is good news, according to Alan Hadden, president at industry organization GSA (Global mobile Suppliers Association), which closely tracks LTE\'s growth. "It will result in larger with larger scale and volumes. That means manufacturers can produce and deliver equipment more efficiently, which should lead to lower costs," he said.

A larger market also attracts more participants, including suppliers, increasing choice and competition, according to Hadden.

So far, operators have launched 24 commercial networks in 16 countries worldwide. A year ago that number was just three, and it is expected to grow to at least 71 by the end of the year, according to the GSA\'s forecasts.

Also, since March, the number of LTE-compatible devices has grown by 64 percent, and now totals 161. Verizon Wireless offers by far the largest portfolio of products. While many other operators just offer modem connectivity, Verizon also offers smartphones and a tablet.

Verizo\'s size helps. But the operator has also been very clear about what vendors can expect from its network, which has made it easier for them to design products. That is something other operators and regulators should try to emulate, according to Hadden.

Clearwire\'s LTE announcement does\'t just highlight LTE\'s momentum, but also the importance of spectrum, and having as much as possible of it. The amount of spectrum an operator has is the basis for the speed it will be able to offer subscribers. More spectrum equates to higher speeds.

Based on its own tests, Clearwire believes it can deliver between 50M bps (bits per second) and 90M bps to users, on average. The lower end of that is on par with what can currently be achieved byTeliaSonera\'s LTE network in Stockholm.

TeliaSonera and Verizon Wireless both use LTE FDD (Frequency-Division Duplex), which sends data over two channels, one for downloading and one for uploading data. TeliaSonera uses 20MHz per channel, allowing it to outperform Verizon, which only uses 10MHz per channel.

Clearwire will also use 20MHz to offer higher speeds. But it using LTE TDD (Time-Division Duplex), which sends download and upload traffic over one channel.

How LTE TDD performs in a real-world environment remains to be seen. There is a lot of interest in the technology, but there has yet to be a commercial launch. And how a mobile network performs depends on a myriad of different factors. But, in general, LTE TDD is more dependent than FDD on an interference-free radio environment to perform at its best, according to Sylvain Fabre, research director in the Carrier Network Infrastructure group at Gartner.

Having lots of spectrum will be even more important in a couple of years when operators roll out LTE Advanced.

A key building block of that technology is a feature called carrier aggregation, which allows operators to bunch together spectrum in different bands and use them as one data link. It would allow Clearwire to further leverage its "vast spectrum depth to create larger \'fat pipes\' for deploying mobile broadband service," the company said.

LTE may be turning into the worldwide de facto standard for 4G infrastructure, but spectrum policy and availability is causing the market for LTE to become regionally fragmented, according to market research company Informa Telecoms & Media.

Informa\'s "LTE Spectrum Strategies and Forecasts to 2016" report lists 10 bands that large operators have or will use to roll out LTE, but there are more that can be used.

The most popular ones are 2.6GHz, 1.8GHz and 700MHz followed by 800MHz and 2.1GHz. Things are made even more complicated by a lack of interoperability on the same band. For example, Verizon and AT&T will both use the 700MHz band, but devices built for one network will not be able to use the other because the operators are using different parts of the band.

For consumers, it means it will take some time before it is technically possible to roam globally on LTE networks. That likely wo\'t be possible until 2013, according Malik Saadi, principal analyst at Informa. Instead, LTE roaming will, if operators decide to start offering it, be limited to smaller regions. Where LTE roaming is\'t available, users will instead have to rely on HSPA (High-Speed Packet Access) or Wi-Fi.

For vendors, the challenge will be to decide which bands they should back, according to Informa. However, LTE has reached a point where spectrum fragmentation is unlikely to have a negative impact on its long-term success, though it will leave some users frustrated, said Julian Bright, senior analyst at Informa.

But even with LTE\'s rapid growth, 3G will still be the dominating mobile technology to access the Internet. To put things in perspective: by 2015, 3G will still account for 70 percent of the revenue from mobile network infrastructure, according to Dell\'Oro Group.