LTE-WLAN Aggregation

LTE-WLAN aggregation (LWA) is a specification developed by the 3GPP. In LWA, a mobile handset supporting both LTE and Wi-Fi may be configured by the network to utilize both the LTE and Wi-Fi links simultaneously. It provides an alternative method of using LTE in unlicensed spectrum, which unlike LAA/LTE-U can be deployed without hardware changes to the network infrastructure equipment and mobile devices, while providing similar performance to that of LAA.

For a user, LWA offers seamless usage of both LTE and Wi-Fi networks and substantially increased performance. For a cellular operator, LWA simplifies Wi-Fi deployment, improves system utilization and reduces network operation and management costs. LWA can be deployed in collocated manner, where the eNB and the Wi-Fi AP or AC are integrated into the same physical device or in non-collocated manner, where the eNB and the Wi-Fi AP or AC are connected via a standardized interface referred to as Xw. The latter deployment option is particularly suitable for the case when Wi-Fi needs to cover large areas and/or Wi-Fi services are provided by a 3rd party (e.g. a university campus), rather than a cellular operator.

LWA has been standardized by the 3GPP in Release-13. Release 14 Enhanced LWA (eLWA) adds support for 60Ghz band (802.11ad and 802.11ay aka WiGig) with 2.16 GHz bandwidth, uplink aggregation, mobility improvements and other enhancements.

Background

Cellular networks have been designed for licensed spectrum. However, as usage patterns changed from voice-centric to data-centric and data usage surged, operators started looking into unlicensed spectrum opportunities. Using WLAN does not only allow operators to increase peak data rate and system capacity, but also to offer services for non-cellular devices, such as laptops.

To cater to operators demand, 3GPP have defined various methods of LTE-WLAN inter-working, ranging from Non-Seamless WLAN Offload (NSWO), to loosely coupled methods such as S2b, to somewhat more advanced methods such as LTE WLAN Radio Level Integration with IPsec Tunnel (LWIP), to ultimately LTE-WLAN Aggregation (LWA).

With LWA, WLAN finally becomes fully integrated into cellular operator's network.

LWA in depth

From the network perspective, there are two options that provide flexibility when looking at deploying LWA - collocated and non-collocated.

LWA design primarily follows LTE Dual Connectivity (DC) architecture [3] as defined in 3GPP Release 12, which allows a UE to connect to multiple base stations simultaneously. In the user plane, LTE and WLAN are aggregated at the Packet Data Convergence Protocol (PDCP) level.


Deployments

On 19 August 2016 Singapore's M1 announced Singapore’s first commercial HetNet (Heterogeneous Network) rollout, including LWA. Through leading edge LTE-WiFi Aggregation (LWA) technology, M1 expects to deliver peak download speeds of more than 1Gbps by 2017.

References

    Further reading

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