There are a lot of things that remain to be seen about how 802.11ax will affect wireless network design. An interesting side effect of the addition of OFDMA to the standard may be an end to the dual 5 GHz access point (AP). In a typical campus wireless network, we don’t need as many 2.4 GHz radios as 5 GHz radios. Rather, we are more limited in the number we can use because the 2.4 GHz spectrum has fewer channels and a larger coverage area. This issue is even more pronounced in high-density wireless deployments.
Rather than just disable the 2.4 GHz radio, some APs allow you to switch the unneeded 2.4 GHz radio to a 5 GHz radio in software. This can be useful because there are a lot more available 5 GHz channels, so rather than having a bunch of APs with only one radio you can add 5 GHz capacity to the network with the same number of APs.
But you might be thinking, if I have the spectrum available in the 5 GHz band can’t I just use wider channels? Because of the nature of 802.11ac operation, you get better performance with more narrower channels. For example, one 40 MHz channel with 100 clients will perform worse than two 20 MHz channels with 50 clients each.
The clients get lower peak performance but have more opportunities to transmit, which reduces latency, jitter, and waiting for clear airtime.
When we move to 11ax, this design aspect of wireless goes away. OFDMA enables a 20 MHz channel to transmit to up to nine clients at once, versus one as in 11ac. It scales pretty linearly as we increase the channel width, with 18 clients for 40 MHz and 37 clients for 80 MHz channels. A single client can also use the entire channel so IT doesn’t have to compromise peak performance for better client density.
Now, if we have the spectrum, we can use a single radio with a wider channel rather than two radios—and service even more clients faster than we could with multiple radios. This means any 802.11ax AP should be able to replace older specialized hardware, simplifying IT’s job and increasing the flexibility of the network at the same time.
About the Author
Ben Thomas has been in the networking industry for more than 20 years, running networks and working for vendors as an Systems Engineer, Consulting Systems Engineer, and Distinguished Systems Engineer….