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Carrier Aggregation: Can 1+1 > 2?

I know it indeed is cliché! But, I can’t help it, because it is true! I am talking about LTE Advanced carrier aggregation. Carrier aggregation is an important step of LTE Advanced. Its first incarnation—aggregation across two 10 MHz carriers—was launched in June 2013. This launch was powered by Qualcomm Snapdragon 800 chipsets with integrated third-generation Gobi LTE modems.

Carrier aggregation is a simple concept: you bond multiple carriers together, so you get more resources per user and hence better data rates and user experience. In a way, it’s “the more, the merrier”—the more carriers to bond, the more resources to the user and hence, higher the performance. LTE Advanced theoretically allows aggregating up to five carriers, yielding peak date rates of more than 1 Gbps.

The first step, obviously, is bonding two 10 MHz carriers on the downlink, as done in the aforementioned launch, enabling a peak data rate of 150 Mbps (Cat 4 devices). But more importantly, this doubles the data rates for users across the cell coverage area, meaning  the data rates that users get are twice those obtained in a single carrier case, whether they are close to the cell or at the cell edge. So, users don’t have to keep moving around, looking at the “bars” on their phones, to get higher speeds.

Increased data rate is straight forward enough. But the next benefit that I will explain is not that obvious, so pay attention! Under typical loading conditions, the increased data rate can be traded off to get twice the capacity or more, on a per-carrier basis for bursty applications such as smartphone usage, social media apps, instant messaging, browsing and others. This means, the overall capacity doubles when you go from two un-aggregated carriers to the same two carriers aggregated. You ask me “How?” Well, the magic term is “trunking efficiency.”

Additionally, carrier aggregation is going to be a crucial tool for operators to utilize the entire available spectrum. As evident, operators will have spectrum in various bands with varying bandwidth. Carrier aggregation will be a glue to bind all of them together. Looking at the possibilities, it is very clear that carrier aggregation will evolve in many directions in the future. There could be aggregation across more carriers, more band combinations—more than 45 being defined in 3GPP. There will be many different kinds of aggregations: SDL (Supplemental Down Link)—aggregating paired and unpaired spectrum; uplink aggregation; MultiFlow—aggregation across cells; aggregation across LTE FDD and TDD, and more

To all the skeptics, asking how will carrier aggregation prosper, my answer is “Go checkout how quickly HSPA+ dual-carrier became mainstream after its first launch.” The case for LTE Advanced carrier aggregation is even stronger, considering the vastly fragmented spectrum bands across the world. So sit tight, and see the places carrier aggregation will go in the future. Meanwhile, if you would like to know more, please visit our dedicated webpage, www.qualcomm.com/ca.

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