This content is part of the Essential Guide: An 802.11ax survival guide: Expectations for the Wi-Fi standard

Wi-Fi 6: How does OFDMA work?

The new Wi-Fi 6 standard works harder but also smarter, thanks to a game-changing feature called orthogonal frequency-division multiple access.

Orthogonal frequency-division multiple access, or OFDMA, puts the high efficiency in high-efficiency wireless -- also known as Wi-Fi 6. While enterprise wireless end users might think they have a need for speed, experts say many performance problems actually hinge on issues with congestion rather than bandwidth.

"We get really sidetracked when we just talk about raw throughput," said Craig Mathias, principal analyst at Farpoint Group. Capacity is more important to minimize latency across all users in a given geographic location on a given channel so they can get their jobs done, he added.

Enter OFDMA, a multiuser variant of OFDM technology that enables a Wi-Fi 6 access point (AP) to connect with many devices at once. OFDMA partitions each radio channel into smaller resource units that it strategically allocates across clients.

In contrast, a legacy AP can communicate with only one user per channel at a time and must hold the line open until a given transmission concludes -- even if there's a delay on the client's end. As a result, wireless performance often suffers in high-density environments like stadiums, conference centers and classrooms, regardless of network speeds.

Every other upgrade cycle was really just a faster version of the previous one.
Zeus Kerravalafounder and principal analyst, ZK Research

Zeus Kerravala, founder and principal analyst of ZK Research in Westminster, Mass., compared each legacy wireless access point to a single checkout clerk and network clients to store customers. Theoretically, the 802.11ac Wave 2 upgrade added three more registers with a feature called multiuser multiple input/multiple output. But, regardless, shoppers still had to wait in single-file lines for service.

OFDMA, on the other hand, fundamentally changes the rules of engagement by allowing each cashier to advance multiple transactions at once -- ringing up one customer's purchase while another signs a check.

"Every other upgrade cycle was really just a faster version of the previous one," Kerravala said, adding that Wi-Fi 6 is the first to fundamentally break the mold.

The pending IEEE wireless standard mandates both uplink OFDMA (UL-OFDMA) and downlink OFDMA (DL-OFDMA). UL-OFDMA allows an access point to simultaneously receive data from multiple clients -- upstream -- while DL-OFDMA enables it to send information to multiple clients -- downstream.

Experts caution that prestandard gear may not be able to implement both features, making it ineligible for the Wi-Fi Alliance's official Wi-Fi 6 certification. Network pros should conduct due diligence before investing.

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