What are the major practical differences between these standards?
The Wi-Fi 6 (802.11ax) 2.4/5 GHz standard introduces OFDMA modulation and data multiplexing, which means that multiple clients can communicate over the air at the same time. This is a very important aspect, because in Wi-Fi each packet transmission (from AP or client) usually has to wait for the air to be free (due to the mandatory CSMA/CA algorithm). This takes time and becomes resource-intensive when many clients are active simultaneously.
Therefore, you can say that in certain cases Wi-Fi 6 can be up to 10× faster simply because of its protocols. Simultaneous communication is possible in both directions, so if acknowledgements need to be sent to clients, this can be done in a single packet.
Another important aspect of Wi-Fi 6 is the use of 2.4 GHz. Until now, this was really only based on the Wi-Fi 4 standard, because Wi-Fi 5 (802.11ac) is a 5 GHz-only standard. The result is especially noticeable at home and in offices: when a client moves from 5 GHz to 2.4 GHz at the edge of coverage, the network is still usable, assuming similar channel spacing and noise floor, which is typically the case in detached houses and, for example, warehouses with sheet-metal walls.
For instance, if you have Wi-Fi calling enabled on your mobile phone, where all calls and SMS messages go over Wi-Fi instead of the outdoor mobile network, you often won’t even notice that the call is happening over a 2.4 GHz channel, because the phone’s bandwidth needs during a call are small.
There are other good technical aspects as well, such as increasing the symbol duration to 12.8 microseconds. In addition, the guard interval (GI) has been increased up to 3.2 microseconds. This significantly improves tolerance to multipath fading and therefore greatly improves indoor coverage quality. Often, the actual throughput at the edge of the coverage area is up to 10× higher than with Wi-Fi 5. If you add wide channels on top of that, this kind of quality-improving feature becomes extremely important.
Energy saving has also improved. TWT (Target Wake Time) can in fact be tuned to spans of days, so IoT clients do not have to stay connected to the network all the time and their batteries last much longer. In practice, the behaviour of a normal smartphone also changes when, at home or in the office, it performs all its activities over Wi-Fi (with Wi-Fi calling enabled).
What happens with the Wi-Fi 7 standard (2.4/5/6 GHz), whose quality adoption has been very slow? First, this standard includes all three frequency bands. In Europe, the lower 6 GHz band with 500 MHz of spectrum is allowed. Second, all frequencies and radios are used for communication simultaneously, so traditional roaming between 2.4 and 5 GHz is no longer necessary. All channels can be used at the same time and data can even be sent in different directions (full duplex).
An important aspect is also the ability to cut out parts of the spectrum from use on a wide channel (for example, 320 MHz) – so-called channel puncturing. This makes it possible to continue using a wide channel even if part of it is affected by interference.
With Wi-Fi 7, most devices operate on 2.4 and 5 GHz at the same time. Especially in Europe, simultaneous operation on 5/6 GHz is quite a demanding RF design task. So far, the only truly linear Wi-Fi devices on the market have been in the Ruckus R670/R750 class, which can even use two channels in the 5 GHz band simultaneously with good quality.
