LTE makes headway on global roaming, speed and voice

The first operators are now rolling out LTE-Advanced functionality, while Swisscom has showed global roaming is possible

By , IDG News Service |  Networking

Carrier Aggregation allows networks to devote more resources to some users by treating two channels in the same or different frequency bands as if they were one. That technique will allow SK Telecom to offer speeds of up to 150Mbps by combining two 10MHz channels. That speed can be achieved without Carrier Aggregation by operators who have 20MHz of continuous spectrum in one band, which is kinder on smartphone and tablet batteries.

"It is true that Carrier Aggregation uses more battery, but what you can do is use clever algorithms to carefully choose when to turn it on," Narvinger said.

The advantages of using Carrier Aggregation will instead become more apparent when operators combine larger chunks of spectrum. Speeds of up to 300Mbps will be possible by marrying two 20MHz channels. The current standards allow for up to five 20 MHz channels to be aggregated. according to SK.

But Carrier Aggregation isn't just about theoretical top speeds: Implementing the technology will also mean improved (albeit lower) speeds even for users who haven't got the perfect coverage needed for the highest speeds, according to Narvinger.

CoMP, the other LTE-Advanced technology adopted by SK Telecom, is used to coordinate and combine signals from multiple base stations to improve both coverage and capacity, especially at the edge of a base station's coverage area. It can be used to improve uplink and downlink quality.

Next year, SK Telecom also plans to add Enhanced Inter-cell Interference Coordination (eICIC), which ensures that signal quality isn't degraded because of interference from a different base station than the one the user is attached to.

The technology can be particularly important when building so-called heterogeneous networks, which use a mixture of traditional large base stations, called macro cells, and smaller base stations to provide additional coverage at busy spots within the macro cells.

Adding small base stations to a network should result in better coverage and higher speeds overall, but it also makes interference more difficult to control. That's where eICIC comes in: Using it decreases interference for users attached to the small cell, at the expense of reducing macro cell capacity. For the technology to make sense, between 60 percent and 80 percent of the traffic has to go via the small cells, according to Narvinger.

A number of other operators including Sprint in the U.S., Telstra in Australia, Optimus in Portugal, Yota in Russia, and Tele2 and Telenor in Sweden have all announced LTE-Advanced trials or roll-out plans, according to GSA. Verizon Wireless plans to start using Carrier Aggregation during the second half of the year, according to spokesman Tom Pica.

LTE has very much been developed with data in mind, but most operators are still dependent on voice revenue, and vendors are making progress here too.

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