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Improve Wi-Fi experience with LTE-U

Posted: 03 Mar 2015 ?? ?Print Version ?Bookmark and Share

Keywords:LTE-U? wi-fi?

In LTE-U, LTE technology over an unlicensed band is paired with a "licensed" LTE signal as an anchor preserving the necessary signalling and handshaking required for a reliable connection.

The thirst for greater bandwidth (and higher data speeds) for our wireless world is unquenchable.

The cellular industry has moved from 2G to 3G and now 4G to offer higher capacity, faster downloads, and better user experience. 4G is enabled through LTE technology that has progressed maximum download speeds from 100Mbit/s (3GPP Category 3) and to 300Mbit/s (Cat 6) last year.

This year, LTE-A (Cat 9) speeds of up to 450Mbit/s are enabled by aggregating three LTE bands for the higher speed.

Operators have to utilise all of their spectrum resources to meet growing market needs. Now, there is a new technology that aggregates a conventional "licensed" LTE signal and a second, LTE-U, signal employing "unlicensed" spectrum to effectively augment capacity.

The LTE-U technology was originally developed by Qualcomm with initial deployment in the same 5GHz spectrum that accommodates Wi-Fi. This implementation provides seamless user experience, better capacity and coverage through a common unified network for both licensed and unlicensed spectrums.

The blended signal provides reliability of licensed spectrum with the capacity boost of unlicensed spectrum. Initially, unlicensed spectrum will be used for only down link.

The 5GHz spectrum employed for Wi-Fi is the U-NII (Unlicensed National Information Infrastructure) U.S. band that many things other than Wi-Fi also occupy (medical/industrial, etc.) and has up to 500MHz available spectrum. LTE-U is ideal for small-cell implementation, with both licensed and unlicensed spectrum coming from the same box. The approach is especially helpful in densely-populated areas.

Joining Qualcomm in LTE-U development are several other companies including Ericsson, SK Telecom, Nokia and Alcatel-Lucent.

A number of cellular operators have expressed strong interest in the technology, including Verizon, T-Mobile, China Mobile, China Unicom, NTT DoCoMo, Deutsche Telekom and TeliaSonera.

With the resulting greater coverage and capacity gains through LTE-U these organisations forecast expanded service offerings and more product sales from the approach. T-Mobile, for example, has begun deploying Nokia's Flexi Zone line of LTE-U small cells indoors, to be followed by outdoor deployments in 2016.

LTE-U, less disruptive than Wi-Fi

Qualcomm claims that LTE-U is less disruptive to Wi-Fi than even other Wi-Fi signals in the same band.

Qualcomm has demonstrated that LTE-U can fairly coexist with Wi-Fi and that the two can work even better together. In countries such as the United States, China, South Korea and India, LTE-U can be deployed based on existing REl-10/11/12 standard along with fair coexistence protocols that Qualcomm calls Carrier Sensing Adaptive Transmission (CSAT). In this scheme, LTE eNodeB base stations (usually small cells) share 5GHz spectrum with Wi-Fi on a time division multiplexed schedule, based on the eNB's dynamic assessment of available bandwidth slices and Wi-Fi traffic density.

Diagram1:LTE-U

For deployments in regions such as Europe and Japan, who have specific channel occupancy requirements called Listen Before Talk (LBT), new standard is needed. The global wireless standards body, 3GPP, is preparing release 13 that addresses LBT requirements. This version of LTE-U is also known as Licence-Assisted Access (LAA) LTE.

In one of the tests (that I witnessed) Qualcomm demonstrated the performance of LTE-U in a very dense deploymenteight pairs of Wi-Fi access points and devices in their stress test room, with only 1m of separation between each of the pairs, all using the same 5GHz channel.


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