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2 September 2019

KT demoes Release 16 specs to support low latency, multi-RAT networks

The next wave of 5G standards, 3GPP Release 16, will add considerable new functionality to the current specifications, particularly in features targeted at new industrial and IoT services. The Release should be finalized early next year, but some vendors and operators are already starting to test pre-standard versions of the new specs to assess the implications for their networks and the services they can support.

Korea Telecom (KT) has been working with Belgian technology company Tessares on a proof of concept (PoC) of a multi-RAT network operating at very low latency. The PoC took place on KT’s live 5G network.

The demonstration focused on achieving very low latency while interworking between 5G New Radio, LTE and WiFi. The cooperation between the three RATs used one of the standards to be included in Release 16, ATSSS (access traffic steering, switch and splitting). This will be part of the Release 16 5G System Architecture Standard (3GPP TS23.501) and was defined with inputs from KT, Apple, Deutsche Telekom, Orange and Cisco.

ATSSS is based on Multipath TCP technology, an IETF standard which has mainly been used so far for combining DSL fixed lines and LTE in converged networks. For instance, Tessares worked with Belgian operator Proximus back in 2016 to trial an LTE/DSL hybrid technology which could lower the cost of connecting the underserved user base.  Multipath TCP enables TCP sessions to spread out across multiple paths for increased redundancy, and also to increase bit rate over networks where bandwidth is constrained, such as cellular.

Its application to 5G in ATSSS aims to improve dynamic switching between WiFi and cellular connections, by reducing the initial session set-up time. This would, in turn,  achieve 5G ultra-low latency across multiple radio networks. In the PoC, set-up delay was less than half that of established approaches, said KT. With Tessares, the Korean operator is leading the international standardization of this initial delay reduction technique through the IETF TCP Working Group.

“The success of this low latency multi-radio access technology test will allow customers to take advantage of existing LTE and WiFi networks, as well as 5G, to enable wireless services at higher speed and quality.” said Sun-woo Lee, SVP of the KT Infra R&D Laboratory.

Tessares is a spin-off from the Université Catholique de Louvain (UCL) in Belgium, which has had several projects focusing on Multipath TCP since it was originally invented 40 years ago.