From February 27th to March 1st, Tessares is exhibiting at MWC’23 in Barcelona. We are demonstrating Wi-Fi Cellular Convergence using our Seamless Handover solution based on ATSSS. We will also be sharing learnings from successful field trials in the US and Europe. Come visit us in Hall 7 at Stand 7.G51

The 5G Changing Landscape

Last year we said that during the Covid pandemic the growth of mobile broadband had continued while ARPU had actually decreased. In the first half of 2022, mobile data growth slowed to 27% year on year and ARPU increased slightly for 61% of operators but only just in time for record inflation to take hold. Operators in developed markets saw 5G speeds decrease for the first time as we reached 1 billion 5G connections globally with expectations of 1 billion additional 5G connections to be added per year from 2023 to 2027.

Fig. 1 – 5G speeds slow down in developed markets for the first time as more subscribers are connected and usage continues to grow, causing network contention. 

Many MNOs and MVNOs are also fixed network operators with millions of subscribers using Wi-Fi at home and at public hotspots. Initiatives like OpenRoaming make it easier for subscribers to access these Wi-Fi hotspots, but most end users do not know or care about which network they use, especially if they have unlimited data plans. It therefore makes sense for operators to use the least cost network.

Field Trials

Our demos, first shown last year, were produced in cooperation with the GSMA Zero Touch Connectivity (ZTC) Task Force which includes operator partners such as BT, Deutsche Telekom, Telefónica, Vodafone and Orange. Going beyond the demos, we have completed several successful field trials in 2022.

Demonstrating Wi-Fi Cellular Convergence at MWC’23

Fig. 2 – Experimental setup schema

For our first demonstration we will measure handover performance for a file download over TCP.  The smartphone is initially connected to a cellular and a download is started. The user moves into an area where Wi-Fi is available and the download continues over Wi-Fi.  We can control the preference for Wi-Fi using a 0-RTT Converter hosted in the public cloud.

Fig. 3 – A download over a 5G connection is offloaded to Wi-Fi without interrupting the download.

Notice that the handover above is overlapping. Without Tessares’ ATSSS solution, the connection would have been lost and data sent over the cellular network would have had to be retransmitted over Wi-Fi. 

High Quality Video Streaming

In the second scenario we will use a 10 Mbps Wi-Fi connection which is not sufficient to carry a 4K 60 fps video stream so we will establish an additional connection to the cellular network (Aggregation mode). This enables the video to be streamed at a higher resolution without any interruptions and reduces 5G usage while providing a level of user experience that would not have been possible with Wi-Fi alone.

When we  leave the area of Wi-Fi coverage, the session continues over 5G. 

Fig. 4 – 4K, 60fps video streaming with insufficient Wi-Fi. Instead of switching off the Wi-Fi, some of the traffic can be carried over 5G. If the user leaves the Wi-Fi coverage area, the video continues uninterrupted.

About The Technology

Multipath TCP (MPTCP) is an extension of TCP which allows one TCP connection to be conveyed simultaneously over several paths, even over different physical networks. MPTCP capable software is embedded on the handset by the manufacturer. This has been the case with Apple and Samsung for a number of years.

The addition of the 0-RTT Transport Converter allows the use of MPTCP which is not normally supported by web servers or applications. This enables MPTCP to use multiple access networks without making changes to applications or servers. The MPTCP connections are terminated by the 0-RTT proxy on a Hybrid Access Gateway located between the server and the smartphone where the networks converge. 

On creating the connection, the client immediately sends a 0-RTT Convert message to the specified IP address and port of the 0-RTT converter. To minimise the latency, 0-RTT Convert protocol uses TCP Fast Open to exchange the address and port of the remote server during the connection’s handshake.

Standards Based Solution

Cellular network operators can deploy 0-RTT Converter servers in their backbone where their networks converge. In the long run, these deployments will migrate to 3GPP ATSSS in the 5G core. Tessares’ “over-the-core” ATSSS solution allows operators to achieve Wi-Fi Cellular convergence today without waiting to upgrade to a 5G core.

Conclusion

Our solution allows a smartphone to move seamlessly between networks for true Wi-Fi Cellular Convergence without negatively impacting the customer experience. Cellular network operators with fixed network assets can take advantage of this solution today without having to wait for an upgrade to a 5G core and with 4G also being supported.

Please contact us if you would like to arrange a call or a meeting to discuss further.