SAN FRANCISCO -- Russian mobile operator Yota bravely stepped out with one of the world's first large-scale WiMax networks in 2008. Making the switch to LTE four years later, when the whole world had already signed on to that technology, may have taken even more courage.
That's because Yota had to turn on its first big-city LTE networks without any testing. The carrier is still trying to optimize its networks to gain the speeds it expected from LTE. But it's still committed to the technology.
Vartan Khachaturov, Yota's chief quality officer, described the company's LTE adventure at the Next Generation Mobile Networks conference in San Francisco on Thursday, where carriers and vendors discussed the promise and challenges of LTE, the world's first globally endorsed cellular technology.
Yota is dealing with many of the same issues facing all mobile operators, including limited spectrum and fast-growing demand for capacity. Like others, it is looking toward small cells and other techniques to keep its service fast and available. But Yota is different from most carriers in developed countries.
For example, the capacity crunch has hit hard at Yota, because it offers unlimited data and its subscribers don't hold back: The average Yota subscriber uses 15 gigabytes per month, and some consume a terabyte per month. And the streaming video that many carriers talk about isn't what's driving that usage. Yota's customers get their movies from file-sharing networks such as BitTorrent.
"It's torrents, and torrents, and torrents," Khachaturov said.
For another thing, when Yota switched over from WiMax to LTE, it replaced all its subscriber's USB modems for free. Some missed the giveaway, which led to the spectacle of three-hour queues to pick up their new gear.
Yota was founded in 2007 and used WiMax, then the only 4G technology, to deploy networks in several cities. But when LTE came along with the endorsement of 3GPP, the standards group behind the widely used GSM technologies, most carriers turned their attention to that system. In late 2009 and early 2010, Yota visited every single vendor of WiMax silicon and asked whether they planned to use the faster WiMax 2 standard, Khachaturov said. Each said it would do so only if Yota committed to a large order. So Yota jumped on the LTE bandwagon.
The advantage would be a much larger ecosystem of suppliers for both network equipment and smartphones and other customer devices. But first, Yota had to persuade the Russian government to allow the use of LTE in the country. Then it helped the government create standards for using it. In the end, the government gave Yota seven months to switch over from WiMax to LTE. All its WiMax cities need to be converted by Sept. 1.
When it embraced the new technology, Yota also decided to get on board with the internationally standard way of using the frequencies it had licensed in the 2.6GHz band. That meant a change from having its uplink and downlink in one band to using two paired spectrum bands. This lets Yota take advantage of FDD (frequency-division duplexing) technology, which gets the most support from network vendors and device makers, Khachaturov said.
The problem was, Yota had to use its existing WiMax band for one half of its LTE network. It proved impossible to run the networks simultaneously and do the transition gradually, because of interference between LTE and WiMax signals. Yota was able to run tests on a small LTE network in one city, but there was no way to turn on a large, citywide LTE system without first shutting down the current WiMax network.
"What we had to do was somehow deploy and LTE network without switching it on at all, and then overnight, we had to switch off WiMax and switch on an LTE network that had never been switched on before," Khachaturov said.
Yota had WiMax networks in five cities, but it went straight to Moscow, where it had about 300,000 subscribers. The company rolled out 1,400 LTE base stations at its existing WiMax sites in a project that took two and a half months. It did some radio planning, but no testing or network optimization until the commercial launch. On May 10, Yota launched LTE in Moscow and one other city, Krasnodar.
"It actually somehow worked," Khachaturov said. Yota later did the same thing in the city of Sochi, and it has two more to go.
However, the overnight swaps from WiMax to LTE delivered far less than the doubling of speed that Yota had expected. Part of the problem was not being able to optimize the network before launch, Khachaturov said. The carrier is still optimizing the network and talking to carriers about how to boost performance.
Meanwhile, Yota is deploying LTE in many other cities across Russia that never had WiMax networks. It's providing 3G coverage elsewhere in the country through a partnership with another carrier, Megafon, which in turn has its customers roaming on Yota's 4G network. Yota offers wholesale services, so other carriers will also be able to use its network.
But the one-time poster child for WiMax has left the technology far behind despite advantages including simplicity and ease of deployment, Khachaturov said.
"I feel WiMax will stay, but it will probably stay as a niche technology."