LTE carrier aggregation gains ground in Asia

How frustrating it is when the video you're watching is often buffering because your cellular service is too slow. Many times, having a quad-core, octa-core or even deca-core application processor may not help. The thirst for more entertainment videos, streaming music, videoconferencing, interactive games, and higher data speeds in general are pushing cellular carriers to enhance their service offerings. That requires greater channel bandwidth for higher-speed down links and, increasingly, up links as well (think videoconferencing like Skype and Apple's FaceTime).

According to Ericsson's February 2015 Mobility Report, application traffic is dominated by video streaming and social networking. In many mobile networks, Ericsson discovered that anywhere between 40% and 60% of the video traffic comes from YouTube. It is predicted that mobile video in general will grow by around 45% annually through 2020 and is expected to account for around 55% of all mobile data traffic. User behaviour is also resulting in video growth driven by other OTT providers like Netflix.

The solution to increasing cellular wireless speeds is carrier aggregation (CA), the mechanism that expands operator capabilities and enhances subscriber mobile experiences and it paves the way to eventual 5G communication. CA is the leading feature of LTE-Advanced (LTE-A).

The spectrum available to the operator is often a patchwork of several different bands, so to achieve higher-speed operation means of stitching together two or more bands is necessary through CA. CA enables combining two or more bands to provide a single channel whose bandwidth is, theoretically, the sum of all of them.

CA is enabled through DSP technology and was formally introduced as LTE-A in 3GPP industry standard Release-10, allowing operators to use their spectrum assets more efficiently to boost user speeds and increase network capacity. Generally, category 6 (Cat 6) defines the better CA capability, enabling 300Mbit/s down link speeds and 50Mbit/s up link speeds.

In November 2014, Qualcomm was the first cell phone chip vendor to announce a category 10 (Cat 10) LTE-A modem supporting global CA for down link speeds of up to 450Mbit/s, up link speeds of up to 100Mbit/s and CA across both TDD and FDD spectra.

Marketing takes over standards

Cellular operators are anxious to demonstrate that their networks are better than those of competitors, forcing them to upgrade their capabilities through CA. As they upgrade their networks from current Cat 4 LTE to, say, Cat 6, they will use terms such as "4G+" as employed by China Mobile or similar nomenclature indicating that their CA service is the better (faster) network. For example, in April 2015 Australia's Telstra Mobile launched the world's first 450Mbit/s LTE-Advanced Cat 9 network. They term their new network capability as 4GX service. Competing Australian operator Optus is also rolling out their LTE-A network, which they call 4G Plus.

According to a recent Global Mobile Suppliers Association (GSA) study, there are 88 LTE-A operators in 45 countries that are at various stages of CA deployment. 14 operators have deployed CAT 4 networks, while 73 have commercially launched CAT 6 systems and 37 of those now support 300 Mbit/s peak down link speeds.

U.S. carriers were late to the party, with the first cellular carrier to widely roll out live 2x carrier aggregation in July 2015 through Sprint. Twenty-nine cities were in the initial roll-out, with more to follow. But, having a carrier that provides CAT 6 (or better) operation also requires LTE-A smartphones. Qualcomm leads the pack in LTE-A modem chips and they are in all of the current CA smartphone line-up illustrated in the accompanying table.