Speed bumps along the LTE road

An online Sidebar to Connected Planet’s cover feature “Is the Industry Ready for LTE?”

Though long-term evolution networks will debut across the world this year, there are still a lot of kinks the wireless industry needs to work out before they’re ready for prime-time wireless services, according to wireless consultancy Aircom.

In its business dealings with wireless operators around the world, Aircom has a unique insight into the 4G plans of carriers big and small, and though there’s little question that the radio access infrastructure is ready to go, there are several elements of the overall network that still need to be hashed out before LTE can meet its full expectations, said Fabricio Martinez, Aircom consulting practice director.

“We will have LTE networks by the end of the year--that’s not a question mark anymore--but when we use the word ‘networks,’ that can mean different things,” Martinez said. Scale will be one of the biggest factors: it will take years before operators build large enough footprints and vendors produce the diversity of devices comparable to what’s available in 2G and 3G today. But there are also technical issues that vendors and operators can only hash out over time, Martinez said.

One of the main issues is that of the scheduler, the element of the network that allots resources to individual data sessions across a network, Martinez said. Many vendors are still using the scheduling technology from 3G networks, which were originally designed with the assumption that at any given time a few robust applications would be consuming moderate to large amounts of data for short yet continuous periods of time—such as would be the model for video streaming. What happened in 3G and with the advent of the smartphone was the opposite tendency, Martinez said: at any given time numerous small applications are access the network consuming small amounts of data very frequently, which creates a nightmare scenario for the current scheduling technologies.  Those problems only become exacerbated on LTE networks. LTE networks will have more capacity, but they’ll also be expected to handle a much greater load of user sessions of varying bandwidth and length.

Vendors like Motorola have already run into the scheduling hurdle in their deployments of the alternate 4G technology WiMax. After a year of deploying and fine-tuning Clearwire’s 4G network, Motorola has managed to refine its scheduling software to handle the shifting session demands of mobile broadband users, Motorola wireless networks general manager Bruce Brda said in a recent interview. “A lot of the things we solved with WiMax 4G networks will directly apply to LTE network,” Brda said. “Some of our competitors have yet to come across those challenges.”

Martinez said he doubts that any vendor has fully solved the issue of scheduling due to the fact that no 4G network—either live or in the labs, WiMax or LTE—has been subjected to the eventual real-world conditions they’ll have to face. Vendors have started improving their scheduling software in 3G to meet the demands smartphones are placing on network resources, but until operators scale up their 4G commercial services to the point where they’re brokering millions of simultaneous daily sessions, there will be no way to test those technologies adequately, Martinez said.

Testing is, in fact, one of the prime hurdles that operators face, Martinez said. While the vendors have been very aggressive in interoperability testing between the handset and the base station, carriers still don’t have a clear picture how LTE will perform throughout the network as a whole, Martinez said.

“When it comes to trials, many times operators can easily test the access network and the eNode Bs [base stations], but they simply don’t have the resources to test it end-to end,” Martinez said. “If you don’t already have a multimedia backbone, how do you test multimedia applications?”

Martinez, however, doesn’t see this as an impediment to the deployment of LTE networks—merely as problems the industry will have to solve as they LTE spreads and the ecosystem matures. Operators know they’ll need the additional capacity of LTE to support the mobile data demands they’re already seeing in 3G, to say nothing of future 4G application demands, Martinez said.

“The reality is they have an immediate need,” Martinez said. “They don’t need new applications. They need to release more bandwidth into the access network.”