LTE in unlicensed spectrum is something I first heard about back in 2014. Since that time interest level in the topic has ebbed and flowed, but has never completely gone away. Recently, however, the topic has started to heat up again, and it appears we are going to see commercial networks using different methods to broadcast LTE over unlicensed spectrum.
For those that don’t remember, when I talk about LTE in unlicensed bands I am referring to LTE-U, LTE-LAA and MulteFire. Both LTE-U and LTE-LAA use LTE in licensed bands for the control channel and 5 GHz unlicensed for the data channel. U and LAA differ in that U does not have the listen-before-talk feature found in LAA. U is basically just for North America where listen-before-talk isn’t required. LAA supports listen-before-talk and can be deployed globally. LTE-U and LAA are both 3GPP standards. MulteFire differs from U and LAA in that it doesn’t have a licensed spectrum component and isn’t supported by 3GPP. This summer has seen a spat of LTE-LAA related news.
T-Mobile launched commercial LTE-U networks across six cities in February. Furthermore, in June T-Mobile trialed LAA achieving 741 Mbps downlink, and plans to deploy it this year. Also in June, AT&T reported hitting 750 Mbps in its LTE-LAA trial, with its own plans for commercial launch by end of 2017. In the month of August, Verizon announced it is in the process of rolling out a commercial LTE-LAA network. The company also reported reaching 953 Mbps downlink speed in a recent trial. Outside of the U.S. (but in June as well), MTS of Russia has been trialing LTE-LAA. For these, and other operators, LTE using unlicensed spectrum helps get them to 1 Gbps LTE. This is a massive change from how mobile operators thought about their networks in the past.
For mobile operators, licensed spectrum has long been king. Unlicensed spectrum was unpredictable. Mobile operators touted the reliability of their licensed spectrum as one of the key advantages over Wi-Fi. Using LTE-LAA and U as part of their 1 Gbps LTE plans shows things have certainly changed in a dramatic way. Of course, not everybody is happy about this.
The Wi-Fi community remains concerned about sharing unlicensed airwaves with LTE, especially the 5 GHz band. The 5 GHz band has been a boon for Wi-Fi. It provides Wi-Fi with more capacity and speed than the smaller and more crowded 2.4 GHz band. 5 GHz is Wi-Fi’s escape from 2.4 GHz, and now it must share it with another wireless technology. But, with the FCC certifying LTE radios for 5 GHz, the Wi-Fi community has little choice but to live with it. FCC certification should provide some guarantee that LTE doesn’t interfere with Wi-Fi in unlicensed bands. Certification doesn’t mean that Wi-Fi won’t eventually be impacted by having to share spectrum bandwidth with LTE. 5GHz does offer more spectrum than 2.4 GHz, but that doesn’t mean it can’t still get crowded.
MulteFire, if it takes off, could have an even greater negative impact on Wi-Fi. Without the need of having licensed spectrum as a gating factor, more entities could deploy it. That would increase the number of networks fighting for access to 5 GHz spectrum. Progress on making MulteFire a commercial reality isn’t as far along as LTE-U and LAA. Field trials of MulteFire aren’t expected until Q1 of 2018. MulteFire, however, does have some industry heavyweights behind it including Ericson, Cisco, Intel, Qualcomm, Nokia and Samsung.
A big reason for Wi-Fi’s success has been unlicensed spectrum. It appears others are waking up to the value of unlicensed spectrum and are willing to challenge Wi-Fi’s primacy to those bands.
Daryl Schoolar is Principal Analyst of Wireless Infrastructure for Ovum. Daryl's research includes not only what infrastructure vendors are developing in those areas, but how mobile operators are deploying and using those wireless networking solutions. Contact him at [email protected] and follow him at @DHSchoolar.