This blog is by Jaakko Huuhtanen at Nokia Networks.
Speed and capacity are the flavors of the moment. The GSA reckons a third of operators are investing in LTE Advanced (LTE-A). There are 88 launched LTE-A networks, 37 of which support the top 300 Mbps downlink speed. There are also 25 networks being deployed or trialed for Category 9 devices, supporting up to 450 Mbps downloads.
Going for higher speeds and more capacity makes harnessing unlicensed spectrum an interesting choice for many. Let’s consider two new LTE-A extensions that already have provisional offers of employment from some operators. Both bring together licensed and unlicensed spectrum to help cellular operators build capacity with free-to-use frequencies. Operators are focusing on these two technologies as they allow for delivery of a consistent service experience over unlicensed spectrum, mainly in the 5 GHz band. And both are being standardized in 3GPP Rel.13.
The first is Licensed Assisted Access, LAA-LTE, which lays down ways to run LTE over unlicensed spectrum to complement LTE on licensed bands. LAA is a technology we have covered previously and which T-Mobile is planning on adopting early.
But let’s talk more about the second option, called LTE-Wi-Fi Aggregation (LWA), which Nokia is also developing to give operators a range of alternatives. LWA enables delivery of Gbps speeds over a combined LTE/Wi-Fi network.
Creating LTE and Wi-Fi companions
Similar to LAA, LWA offers more control than simple Wi-Fi offload because it integrates Wi-Fi with the LTE Radio Access Network (RAN) and thus allows for a guaranteed level of service and Gbps speeds.
In LWA, the LTE network has the option to use Wi-Fi radio for additional data downlink to boost the downlink traffic. LTE can coordinate the use of the Wi-Fi downlink based on the radio signal strength and the traffic load to make optimum use of both LTE and Wi-Fi radios. Uplink communication, in turn, takes place on the licensed LTE spectrum. This means that subscribers receive a significant performance boost on downlink with the added Wi-Fi layers, while the LTE layer guarantees good performance even when the Wi-Fi layer experiences congestion. The LTE RAN integration enables operators to allocate traffic and manage mobility according to real-time traffic conditions and interference levels. All traffic, whether over unlicensed Wi-Fi or licensed LTE, is treated the same way by the core network. This makes Wi-Fi a secondary carrier to LTE and simplifies deployment.
LWA will be a good neighbor for the other users of unlicensed spectrum. Because Wi-Fi already uses a well-established spectrum sharing mechanism in the shape of listen-before-talk (LBT), LWA will ensure fair use of unlicensed spectrum according to this common regulatory requirement.
LWA project to run this year in Korea
Korea Telecom (kt) and Nokia are running a Proof of Concept (PoC) using Nokia Flexi Zone small cell solution and LWA to demonstrate how unlicensed Wi-Fi spectrum can be exploited cost efficiently to achieve Gbps peak data speeds and consistent service experience over unlicensed spectrum. The project aims also to show how kt could leverage its huge installed Wi-Fi base to help meet growing mobile broadband demand over LTE and deliver even better customer experience using additional capacity on the network.
Changseok Seo, Head of Network Strategy Business Unit of Korea Telecom comments:
“As well as deploying new small cells, we want to leverage LWA with existing hotspots to make even more efficient use of our current investments. kt will also continue to steadily develop the technology to lead the world market in the field of LWA with Nokia Networks. Partnering with them allows us to evolve our networks beyond 4G as we prepare to enter the 5G era.”
If kt’s enthusiasm for LWA catches on with other operators, we won’t be surprised to see the technology becoming one of the mainstays of LTE aggregating with unlicensed bands.
It is clear that mobile operators have a growing range of technology options to draw on as they race to meet demand and prepare for the 5G era by tapping into the large unlicensed spectrum bandwidth. As this kt case shows, partnering with Nokia Networks is an easy way to extend the benefits of existing LTE networks into this spectrum, improving both user experience and cost efficiency.
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