LTE Advanced carrier aggregation's pitfalls are few and far between

Tammy Parker, FierceWirelessTech

It's been one year since South Korea's SK Telecom became the world's first carrier to activate LTE Advanced carrier aggregation with a commercial smartphone available for use with the service. That anniversary prompted me to ask around about any pitfalls to this technology that carriers and vendors may have come across now that there is a year of carrier-aggregation experience under the industry's collective belt.

Carrier aggregation enables an operator to combine component carriers to create larger chunks of bandwidth. Operators are starting by aggregating two carriers, but specifications allow for the aggregation of up to five component carriers, each a maximum of 20 MHz, to attain a total transmission bandwidth of up to 100 MHz. (However, Nokia (NYSE:NOK) and SK Telecom recently demonstrated the aggregation of 10 spectrum frequencies allocated for both FDD and TDD variants of LTE to create 200 MHz of bandwidth and deliver a throughput speed of 3.78 Gbps.)

Carrier aggregation primarily offers operators increased capacity, higher peak speeds and improved load balancing on their networks.

4G Americas reports that eight carriers in six nations (including all three South Korean mobile operators) have deployed LTE Advanced. The only U.S. operator on the list is AT&T Mobility (NYSE: T), which acknowledged in March that it has activated carrier aggregation for its 700 MHz and AWS spectrum in Chicago and some other markets. But Verizon Wireless (NYSE: VZ) and Sprint (NYSE: S) are also gearing up to deploy carrier aggregation later this year, so the wheels are starting to roll for broader adoption.

For the most part, people indicate few issues with carrier aggregation. Oh, sure, there's the fact that an end-to-end carrier-aggregation service requires compatible devices, and those aren't immediately available for every market, but that is a common issue with any new technology.

"Carrier-aggregation-enabled devices up to Category 4 were available very quickly," Eric Parsons, LTE product manager in Ericsson's (NASDAQ: ERIC) networks business unit, told me. "Category 6 devices are now becoming available and commercially launched.

"Device availability is always a factor for operators that focus on technology leadership, but the emergence of advanced smartphones that can leverage our operators' carrier-aggregation-enabled networks has a rising-tide effect, improving the experience for all users on the network," he added. "Carrier-aggregation-enabled devices are like cars in the carpool lane. Yes, they get a better experience, but they also free up space for cars in the other lanes, too."

However, Parsons said a much bigger issue is the need for network optimization that maximizes the battery life of carrier-aggregation-enabled devices. "Always-on carrier aggregation will drain battery life, so the network must employ intelligent algorithms to know when it's best to apply carrier aggregation, based on end-user data activity and network conditions," he explained.

In addition, problems can arise whenever there is a mix of high-band and low-band aggregation, which, Parsons noted, "can create challenges with regard to coverage parity," because of the bands' different propagation characteristics.

"This necessitates careful carrier-selection algorithms that ensure that each device is on the best carrier given the current load, network conditions and device carrier-aggregation capabilities," he said.

Emilio Diarte, Nokia's head of technology in North America, indicated that operators deploying carrier aggregation first need to optimize and automate their networks. "It is a complex functionality that involves the network to dynamically make decisions about which user is going to use carrier aggregation, what parts of the spectrum the user is going to be allocated and other dynamic factors" that require management and optimization, he said.

Clearly, deploying carrier aggregation is not akin to a casual walk in the park, but it appears that most potential issues can be resolved with some dedicated optimization and fine-tuning of the network.

Diarte acknowledged that there is an ongoing learning curve as operators deploy carrier aggregation. But he added: "To me, carrier aggregation is a very logical evolution of the network, and I don't think anybody should disregard carrier aggregation because of its complexity."

Ultimately, the long-term positives of carrier aggregation far outweigh any potential short-term negatives. That is why carrier aggregation will most likely be arriving in a major market near you sooner rather than later.--Tammy

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