The eICIC on the LTE-Advanced Cake
In the rush to get mouths watering over faster mobile data, providers have begun to deploy carrier aggregation (CA) and advertise it as LTE-Advanced. It’s caused a bit of confusion and frustration because it’s only one of the several features that define true LTE-Advanced, but it’s a biggie.
“Carrier aggregation is a key feature because it’s how carriers will best take advantage of additional spectrum bands, for example AT&T with the WCS band and Verizon with AWS,” telecom analyst Peter Rysavy said.
Besides the benefits CA brings in consolidating fragmented spectrum assets into more useful, fatter pipes, the technology can provide a boost to data rates as well as increase capacity.
Rasmus Hellberg, senior director of technical marketing at Qualcomm, said that aspect is often overlooked because people are considering it from a 100-percent usage scenario for carriers, which would only really happen if all users were constantly downloading. Because usage more typical comes in bursts, aggregating carriers can either be used to achieve higher rates or more capacity, but not both at the same time.
“There’s a trade-off that’s possible when the carrier is partially loaded,” Hellberg said. “If you squeeze in the same number of users that you have in two single carriers into a wider carrier, these guys would have double the data rates. But you could also take twice as many users with the same user experience that we had before.”
So carrier aggregation has a lot of benefits, many of which SK Telecom touted when it in June announced its LTE-Advanced network, which it deemed the first of its kind to be publically available. Despite the carrier aggregation-based advances SK Telecom proudly proclaimed, the Korean provider was sure to point out its plans to apply enhanced Inter-Cell Interference Coordination (eICIC) by 2014.
To hear Hellberg tell it, there’s a common agreement in the wireless community that LTE-Advanced that there are three features coming in Release 10 and beyond: CA for leveraging wider bandwidth, Multiple-Input Multiple-Output (MIMO) for leveraging more antenna power and eICIC for leveraging heterogenous networks (HetNet) and small cells.
Hellberg says the industry tried to promote eICIC as range expansion, because it’s easier to say, but that eICIC moniker encompassed more of what the technology can do.
The first piece of eICIC, Hellberg said, is on the network side and consists of coordinating how carriers transmit. When eICIC is applied, it works to optimize the performance of small cells within the macro-cell, effectively boosting the signal range of small cells without using more power. Hellberg explained the effect in terms of time division technology and said that in instances when the macro-cell doesn’t use a time slot, the time slot can in turn be used exclusively by one or smaller cells, which provides the aforementioned capacity and range boost.
“But to make this really work, you also have to combine it with advanced receiver devices,” Hellberg said, which brought him to the other piece of the puzzle on the device side that involves building interference cancellation into connected devices.
“If you have this feature, a device can discover a small cell much further away than if you didn’t have it,” Hellberg said. “What’s the use of having small cells if no user can discover it and use it?”
Rysavy concurred with Hellberg’s assurance that eICIC will be vital to the growth of small cell deployment as it’s related to LTE-Advanced.
But Hellberg looked even further out to note eICIC’s role in Qualcomm’s 1000x initiative, a plan make network performance 1,000 times better over the next 10 years. He said that adding more small cells is a key component of 1000x and that eICIC will help make sure the small cells do what they’re supposed to.
“When you add more small cells you have to make sure you get more capacity by doing it. If you just more and more small cells, you get more interference so the capacity is not scaling completely with the small cells added,” Hellberg said. “So, eICIC is becoming very important going forward.”