LTE-U: Frequently Asked Questions

By: David Young

Recently, I wrote about the exploding demand for mobile broadband that is driving the need for more spectrum, both licensed and unlicensed, and an exciting new unlicensed technology (LTE-U) that is being developed to improve consumer’s mobile broadband experience.

Although everyone is eager for even faster, more reliable - simply better - mobile broadband, and excited about new technologies that can deliver better broadband, I do get questions from some people about LTE-U so I thought it might make sense to answer some of them here.

Q: I've been told that LTE-U will harm Wi-Fi. Is that true?

A: No. LTE-U was designed from the ground up to play nicely with Wi-Fi. Extensive testing has shown that adding a new Wi-Fi hotspot actually causes more interference to existing Wi-Fi than adding an LTE-U node would cause.

Q: But LTE-U could use up all of the unlicensed spectrum and crowd-out Wi-Fi, right?

A: No, there is plenty of unlicensed spectrum used by Wi-Fi that is not used by LTE-U. For example, most Wi-Fi equipment in use today operates on 2.4GHz which LTE-U does not use at all. In 5 GHz, half of the channels used by Wi-Fi aren’t used by LTE-U either. And of course, when LTE-U does use channels that are shared with Wi-Fi, it does so fairly.

Q: I’ve heard that LTE-U is not “polite” and doesn’t “listen before talking.” So how can LTE-U share the spectrum fairly with Wi-Fi?

A: LTE-U is actually extremely polite. First, it listens to find a channel that is not being used. Even on an unused channel, LTE-U will still repeatedly stop and listen again to be sure someone new doesn’t want to use it. In the unlikely event that there are no completely unused channels, LTE-U will select the one that is being used the least and then share it by taking turns. The co-existence mechanism LTE-U uses for taking turns sharing a channel is different than the method Wi-Fi uses, but in practice, the two approaches work very well together.

Q: Doesn’t LTE-U have to go through an official standard setting process?

A: The FCC’s rules for unlicensed technologies do not require standardization and, in fact, there are many proprietary technologies operating in unlicensed bands today. As long as a new device meets certain basic rules – which LTE-U does – it can freely operate in unlicensed bands. That said, there are benefits to standardization with respect to economies of scale and global interoperability, which is why LTE-U uses the existing global standard for LTE, which was developed by the 3GPP (a standard setting body similar to the IEEE).

Q: If a new standard is being developed, why not just wait for that?  What’s the rush?

A: The work currently underway with LTE-U is providing real-world experience that will help improve the next versions of the 3GPP standard. But more importantly, because Better Matters. Consumers don’t want to wait for better, they want it now. LTE-U provides a better mobile experience, and it won’t adversely impact Wi-Fi or other unlicensed technologies. There is no reason to delay providing consumers with a new option for better service.

David Young has an engineering background, which enables him to develop positions on emerging public policy issues and asses key technology and communications industry trends. Prior to 2000, he spent six years working in Verizon’s Research and Development (R&D) group on many advanced technologies including VoIP, data network architectures, and audio, video and image compression. He has been awarded ten U.S. government patents for his R&D work. David is a member of the IEEE and IEEE Communications Society.