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Every new wireless standard presents a fair amount of potential confusion to untangle.
The latest wireless standard, 802.11ax, also known as Wi-Fi 6, is now appearing in consumer hardware and starting to see early enterprise adoption. As a result, client device compatibility is one of the more frequent questions that comes up.
The actual standards are written by the Institute of Electrical and Electronics Engineers (IEEE). The Wi-Fi Alliance does not write the standards, but it performs limited interoperability testing and issues various certifications based on the IEEE's work. And, to date, each new standard has backward compatibility as a fundamental construct.
So, yes, Wi-Fi 6 backward compatibility is possible with previous wireless standards and devices. But, as always, there's more to the story.
The problem with full backward compatibility
If you come to one of my wireless LAN (WLAN) environments with an older 802.11b device, you won't be able to connect. Why not? After all, I run 802.11ac wireless access points, and they promise backward compatibility with legacy clients. In reality, though, the standard is not the final word, and this holds true with 802.11ax.
Backward compatibility sounds nice on the surface, but it comes with a performance penalty that can drag down the lofty speeds promised by standards such as 802.11ac and now 802.11ax. The deeper technical explanation is beyond this quick explanation, but it comes down to optional data rates.
Some legacy client devices need the likes of 1 Mbps and 2 Mbps enabled on the WLAN to function. Many wireless networking professionals who run big Wi-Fi environments have had slower rates administratively turned off for several years to let the higher data rates prevail.
So, is Wi-Fi 6 backward-compatible? Yes and no.
By definition, the standard says absolutely yes. In reality, however, most networks are going to be configured in the name of performance tuning to skew away from total backward compatibility.
Generally -- but exceptions exist -- 802.11b rates of 1, 2, 5.5 and 11 Mbps are disabled, and some environments also block some or all 802.11g rates as well. Most newer client devices will be minimally capable of 802.11n, but unfortunately, some of the more ill-conceived devices rely on cheap wireless chipsets and backward compatibility, which leads to frustration for both the device user and network administrator.
Dig Deeper on Wireless LAN (WLAN)
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