Is Wi-Fi about to compete with LTE on QoS? If that did happen, of course, it would beg an obvious question: if they do the same thing why do you need them both? LTE and Wi-Fi are always distinctly different – or were. That’s because until recently there was a significant difference in the way wireless transmission was controlled (versus not controlled) as well as operating in licensed versus licence exempt spectrum.
Not long ago MNOs were dismissive of operating in licence exempt spectrum. Then Wi-Fi became a convenient way to offload data traffic from their congested networks, especially in dense areas. By now licence exempt spectrum is enormously popular; that’s why we’ve been talking about it, and especially about LTE-U, MulteFire and LAA-LTE.
Wi-Fi – even if appreciated for data offload – is generally not seen as carrier-grade solution that could support quality voice services, but VoWiFi is starting to grow as an MNO offering. Interference is one of the potential issues. The other challenge is the current access methodology of Wi-Fi, based on its random access element that meant that other user transmission would stop (and back-off for a random time before attempting to transmit again) when somebody else is transmitting. Think Hawaii and Aloha!
The 802.11ax Wi-Fi standard however changes all of that. It introduces a controlled access methodology (OFDMA) into the Wi-Fi standard. OFDMA allows air interface control by scheduling of transmission, e.g. in which sub-channel and at what time a user device is allowed to transmit. The access point can now not only control the downlink but also the uplink which was historically the difficult bit – especially in a TDD system where you have uplink and downlink on the same frequency. OFDMA in both directions solves that problem.
OFDMA is of course already used as the access methodology in LTE. But the 802.11ax standard that will bring OFDMA to Wi-Fi is progressing. Common features of LTE – such as multi-user MIMO – are now part of the latest Wi-Fi standard, enabled by OFDMA. Quality of service and carrier-grade voice could be supported as 802.1ax enabled devices penetrate the market.
And yet we have been here before. Interestingly WiMAX was an OFDMA based technology, but LTE prevailed. On the other hand, this is Wi-Fi. I wouldn’t expect LTE to swallow up Wi-Fi – both are strong standards, and the economics are fundamentally different. Mobile network operators will keep on building and upgrading their LTE (and LTE advanced or future 5G) networks based on licensed spectrum. And the consumer side will continue to take advantage of technologies in unlicensed spectrum, particularly ones that have just made a massive step forward in terms of performance and efficiency due to the introduction of Wi-Fi 802.11ax. But I wonder what this will mean for LTE-U, MulteFire and other LTE approaches to licence exempt spectrum? How will they address the potential challenge of 802.11ax if – and it’s no longer a big if – it emerges as a viable commercial solution? As ever the ultimate driver here is who will monetise this new technology first?