Wi-Fi links on unlicensed wireless bands have become an essential tool for consumers connecting to the internet, whether at home linking to cable or fiber networks, or sipping coffee at Starbucks. As the speeds of commercial internet services have increased, Wi-Fi standards have kept pace, despite growing shortages of unlicensed spectrum to support them. The developers of the latest Wi-Fi 6 standard (IEEE 802.11ax) have put more emphasis on getting around the spectrum limitations.
“The main goal of the specification is really about using the spectrum more efficiently,” said Wi-Fi expert Kenneth Fernandes, author of wifiblog.com, during a webcast yesterday hosted by USTelecom.
Most consumers today use Wi-Fi 4 (802.11n introduced about 10 years ago) or Wi-Fi 5 (802.11ac introduced about five years ago) devices. The 11n devices operate mainly on the crowded 2.4 GHz unlicensed band and the 11ac devices on the rapidly populating 5 GHz unlicensed bands. The 11ax devices will operate on 2.4 GHz, 5 GHz as well as the 6 GHz, which many anticipate will be available for unlicensed use within the next 12 to 18 months.
Wi-Fi 6 increases speeds slightly above the approximately 700 Mbps top rates of the earlier two standards. But its greatest advancement is the ability to operate over multiple devices simultaneously. In earlier versions, the access point using Orthogonal Frequency Division Multiplex (OFDM)
Modulation links with only one client device at a time. Wi-Fi 6 uses a different digital modulation technique – Multi-User Orthogonal Frequency Division Multiple Access (MU-OFDMA) – that allows the access point to connect to up to nine clients at once, in effect creating more streams in high-density environments.
Fernandes compared OFDM and MU-OFDMA using a truck delivery analogy. (See graphic below.) “With OFDM you have three tractor-trailer trucks, with one carrying a web page, another is carrying some streaming data, which is a little larger, and the other is just a small little instant message. With 11ac we need three trucks to send those,” he said. “With OFDMA, we can now pack it all in the same truck … Overall, it increases efficiency and reduces latency.”
The new standard also increases efficiency with other features, such as “basic service set coloring,” which mitigates co-channel interference when Wi-Fi users in proximity operate on the same frequency. “Target wait time” is a technique for improving battery life. The “longer OFDM symbol” increases access point coverage areas. Wi-Fi 6 also incorporates the latest Wi-Fi security standards.
“There are limited clients available today in 11ax … I’m only aware of one client on the market today, which is the Samsung Galaxy S10,” Fernandes said. Others should be available in coming months. Wi-Fi 6 is backward-compatible with earlier Wi-Fi standards; however, the spectrum efficiency features of the new standard do not work on older client devices. There will be little point to transitioning to Wi-Fi 6 until a user or company can obtain corresponding clients.
The Wi-Fi 6 standard currently is in draft form. Fernandes said that the IEEE is likely to ratify the standard in the second half of 2019 with equipment certifications by the Wi-Fi Alliance likely to follow within a few months. Some pre-standard 802.11ax devices have been available to some enterprise companies for about a year. However, Fernandes said that using those devices could be risky because they might not be software upgradable when standard devices become widely available.
For those that would like to learn more about the next generation of Wi-Fi, USTelecom is making a replay of the Fernandes presentation available online.