5G and WiFi will come even closer in the dense HetNet of the 2020s

There are different schools of thought about how 5G and WiFi will coexist.

At one extreme are those who think 5G will make WiFi redundant after a few years because it will overtake the 802.11 family in speeds, support better latency and QoS, and be available in shared as well as licensed spectrum.At the other are those who think WiFi, which has its own forward-looking roadmap of standards, will limit the impact of 5G because it is hitting some of the key milestones earlier – for instance, with the high device density envisaged for the imminent 802.11ax release.

The most likely outcome is an extension of what has happened in 4G over the past couple of years – a blurring of lines between the two technologies (WiFi improving its QoS, LTE moving into unlicensed bands), but an enduring requirement for both. The 3GPP and IEEE have very different standards processes and starting points, and this results in complementary platforms, each with its own strengths. It is highly probable that, in the 5G era, WiFi and 5G New Radio (NR) will both find their place in a broader multi-network landscape.

The benefits of this multi-standard approach will be increased, for service providers and users, if there is deeper convergence between the technologies than there has been in the 4G era. Cellular/WiFi coexistence has often consisted of data offload from cellular to WiFi, to reduce costs for MNOs; or the two radios living side-by-side in most handsets, allowing the end user to choose their connection.

SCF was an early and active participant in moves to allow for more intelligent interworking, and was well placed to take a lead because the highest levels of WiFi/cellular cooperation often take place indoors, between small cells and access points. Back in 2014, it was exploring use cases and technical specifications for coexistence, and in 2016, the Forum established a joint taskforce, with the Wireless Broadband Alliance. Its first major deliverable was the first comprehensive architecture specification for integrated small cell and ‘trusted’ Wi-Fi (ISW) networks (SCF178).

It is logical, then, that SCF should continue to work on WiFi interworking into the 5G era. The TECH working group has selected this as an important work item, within SCF’s broader work plan for 2018-2019. This plan rests on three pillars – global technology alignment, enterprise engagement, and policy for densification. WiFi/5G interworking will be relevant to all these, but most prominently in the first one. It will be vital, in the hyperdense HetNet environment envisaged for the 2020s, that common interfaces and protocols are agreed not just for small cells in the 3GPP arena, but between those cells and other relevant technologies.

That will make it very important for SCF, and the TECH working group, to continue to cooperate with partner organizations on the WLAN side of the industry. This will ensure that common requirements are identified and that work by either side can be acknowledged and supported, leading to a seamless multi-network platform.

This will be particularly important as standards for 5G in unlicensed spectrum are unlikely to be finalized until Release 17 of the 3GPP’s specifications, so WiFi – along with LTE in shared bands – will be an important way to increase spectrum capacity in a given location, at low cost.

Several approaches to 5G/WiFi interworking and integration are being explored within SCF, WBA, 3GPP and IETF, to name a few of the bodies with an interest in this complex area. They fall into three categories, all of which have their foundations in 4G, but are being enhanced for a more dynamic approach in 5G.

The categories are access-centric integration, such as LTE-LWA (LTE WLAN Aggregation); core-centric integration, such as the evolved packet data gateway (ePDG) in the 4G core; and above-the-core integration, such as Multipath TCP.

While the standards bodies will work on 5G migration paths for these and other technologies, the important work for SCF and its partners will be to apply those standards specifically to small cells, to ensure they are practical and deployable in dense HetNets; and to assess performance requirements, interoperability levels and use cases.

Over time, the issues of WiFi/5G interworking will become part of a far broader and even more ambitious roadmap – towards a fully dynamic multi-network framework in which traffic can be routed intelligently over many connections, and in which many radio technologies are harnessed to create virtualized network slices.