Seamless Wi-Fi offload

The crucial role of Cellular Wi-Fi offload

Cellular video traffic is expected to grow by 34% year-on-year, mainly driven by the insatiable appetite of millennials for online streaming. With this rise in data consumption and the intense competition between network operators, including the emergence of unlimited packages, the price per GB carried is putting unsustainable pressure on margins.

As shown in fig. 1 from Cisco’s VNI report, Wi-Fi offload already carries a significant amount of traffic and will be essential in coping with the future cellular traffic explosion. That is why MNOs and MVNOs are busy trying to offload as much mobile data traffic as they can in order to save network costs.

Fig 1 – Cellular / Offload traffic forecast

Managing cellular & Wi-Fi handovers when offloading

MNOs and MVNOs largely deploy Wi-Fi hotspots in order to offload traffic from cellular networks. Introduction of Hotspot 2.0 or Passpoint has significantly improved user experience by delivering seamless roaming between Wi-Fi networks. However, seamless handovers between cellular and Wi-Fi networks cannot be delivered without a real convergence between networks.

Fig 2- Evolution of Wi-Fi offload customer journey

As discussed previously, cellular and Wi-Fi networks are playing a key role in mobility. In the ongoing 3GPP Release 16, the standardisation body has specified a function of the 5G core called ATSSS which manages the convergence between 3GPP-networks (such as 5G) and unlicensed 3GPP networks (i.e Wi-Fi), turning heterogeneous networks into one converged network.

ATSSS (Access Traffic Steering, Switching & Splitting) (fig. 3) offers new capabilities to deliver an improved user experience for the Seamless Handover use case. In support of such Wi-Fi offload our focus is on Steering & Switching.

In some situations, neither Wi-Fi nor cellular networks deliver a stable connectivity. Therefore, the Splitting feature can be useful as it improves reliability of the connection by combining available wireless access.

Fig. 3- ATSSS capabilities and the benefits for the end-user

ATSSS uses Multipath TCP (MPTCP) technology, a standardised evolution of TCP which allows a single data connection to use several paths simultaneously for greater connectivity.

Introducing the ATSSS overlay by Tessares

Tessares has long standing MPTCP expertise, from the protocol’s genesis through to many successful MPTCP hybrid access deployments, designed to boost the broadband speed of slow DSL by combining DSL+4G.

Recently Tessares & KT successfully tested a 5G ATSSS service in KT’s 5G commercial network. Notably, with its ATSSS overlay solution, Tessares can provide seamless Wi-Fi offload today with existing cellular (4G) and fixed infrastructure.

This overlay solution comprises two elements (fig. 4):

Smartphone component: The ATSSS app installed on smartphones
Network component: The ATSSS overlay backend ‘Hybrid Access Gateway’ (HAG) placed between the cores and the Internet so it can be reached by the device through both cellular and Wi-Fi networks

Fig. 4- ATSSS overlay – Architecture overview