The newest thing in WiFi is 6 GHz. Some vendors and articles are hailing this as the greatest thing to happen to WiFi in recent history. While this is a huge advancement for the industry, let’s take a step back and look at all the aspects of designing for 6 GHz. Let’s first look at the characteristics of radio waves in general. There is a general rule and frequency increases the wavelength decreases. For me, this principle was driven into my head in my physics 107 class many years ago now. I currently reside in a suburb of Buffalo NY, having grown up here we always heard about the WKBW “Buffalo’s most powerful radio station”.[i] For those of you not from the area this was the first 50,000-watt radio station on the AM band. On clear nights without cloud cover, there were reports the signal could be heard as far south as Florida. I even found a site that references it being able to be heard in Sweden.[ii] Why did I bring this up when I started talking about Wi-Fi? This general principle will guide the general rules for each “Wi-Fi frequency band” that we are going to explore, as frequency increases the distance it will travel with the same power decreases. Below is a chart that illustrates this better than any I could make. Being that WKBW radio was in the AM band these were a lower frequency and had longer waves, this allowed it to pass through obstacles more effectively while retaining data-carrying integrity. This same principle will guide us as we explore the 2.4 GHz, 5GHz, and now the newest 6 GHz bands.
Let’s first look at the oldest Wi-Fi band 2.4 GHz. The band was first introduced to the IEEE in 1997. When this band was first used for Wi-Fi it only supported 1 and 2 Mbps. When Wi-Fi was first introduced it was more of a convenience and it couldn’t handle large amounts of data efficiently. One of the benefits of the 2.4 GHz band was that it can easily pass through surfaces, such as drywall. As Wi-Fi begin to catch on the standards were improved to increase the throughput available on this very narrow band. The band that is available for Wi-Fi is only about 94 MHz wide. In the United States, it is even less than that, closer to around 72 MHz. This leaves very little room for even the most efficient standards to be able to transmit large amounts of data.
This now leads us over to 5 GHz. I often skip over 802.11a which existed on this band but was not commonly used in the United States from my deployment experience. This has to do with the clients not being as common, the chips to manufacturer 5 GHz clients being more expensive, and the ultimate fact that 5 GHz simply didn’t cover as well as 2.4 GHz. The characteristics of 5 GHz are that it started out using a wider band and it had newer modulation techniques that didn’t have to remain compatible with older standards. This was soon to become the workhorse starting in the newer standard of Wi-Fi 4 (Wireless N). This was the first standard that contained both 2.4 GHz and 5 GHz bands on the same standard. This is where the challenges for designing dual-band Wi-Fi began. Since 5 GHz more than doubled the frequency of the wave, this also means that the wavelength deceased. This makes coverage cells smaller than on 2.4 GHz. Therefore, we need to deploy more APs in an environment to cover 5 GHz than we do on 2.4 GHz. True 5 GHz has more channels than 2.4 GHz does, but the band often overlaps radar, some of which are required for weather and airports, reducing the number of channels when this occurs. With the shorter wavelength of 5 GHz, this also means the signal derogates faster and doesn’t pass as easily through some materials.
With users quickly filling up the 5 GHz band there is a new 6 GHz band that has been cleared of previously designated traffic for its new use, Wi-Fi. This band uses an even shorter wavelength than 2.4 GHz or 5 GHz, making the coverage cell even smaller than any previously deployed band. 6 GHz does have some things going for it. First, it is a fresh band. This means that any previous traffic had to be cleared off of it, and there aren’t any legacy Wi-Fi standards that need to remain compatible with. On the 2.4 GHz and 5 GHz bands, if there are older clients that do not support the newer standard available on the AP (assuming the AP is newer than the clients) it can trigger protection mechanisms. These could be as simple as having extra headers such as when Wi-Fi 4 and Wi-Fi 5 clients both exist together. If there are even older clients, it could cause RTS/CTS frames between each transmission slowing the entire medium, as seen with 802.11b devices. The benefit right now with 6 GHz is that there aren’t Wi-Fi clients competing for airtime. In my opinion, the people on the IEEE have seen the issues when you have to account for older generations of devices of Wi-Fi and will hopefully plan the best they can for a more efficient band as newer generations emerge. As of writing this, I do not know of any client device yet available on 6 GHz.
This brings me to the main point, which band is best to plan for right now. While there is no doubt that 6 GHz is the way of the future, it is too early to declare that this is our primary band. While I have no doubts in the near future it will be a workhorse, I am designing my networks around 5 GHz. While 5 GHz does have its downsides, we simply are ahead of what clients can support.
While some of the major Wi-Fi design programs have teased, but have not officially stated, that their software will soon be able to support 6 GHz, we do not have a good way to model for it. In other words, instead of trying to manage two bands on an AP, where we wind up shutting off about half of the 2.4 GHz radios to prevent CCI and an increased noise floor, we are going to have to contend with three bands now. It is my belief that we are going to have a denser deployment of APs in an environment, just to have proper coverage of 6 GHz, and by my estimation about 25% will need to have the 5 GHz radio turned off, not to mention between 60-70% of the 2.4 GHz radios turned off. That is assuming that they are tri-radio APs. With that assumption, we also will need to address the increased power consumption of these APs. Even with the larger Wi-Fi 5 APs 802.3at (30 watts) sometimes struggled to power some models of APs. These newer APs I am going to assume will need 60 watts or even possibly 90 watts of power, not to mention the increased potential throughput. Planning for the 6 GHz band could require a complete overhaul of the network, Switching, firewall, and possibly even wiring. It is my opinion that if the customer regularly keeps updating to the newest clients, or there is a need for greater data throughput right now; then we plan for 6 GHz as it stands. If the customer has legacy or even current clients, as of the time or writing this to my knowledge, none exist. Therefore, it is a moot point planning for 6 GHz at this time, if they have a well-designed and functioning network. 6 GHz is a major leap forward, but let’s not put the cart before the horse and deploy something because it is the newest, but deploy it because it is the right solution.
[i] Buffalo’s most powerful station
[ii] https://rockradioscrapbook.ca/arc-jan22.html
Bibliography
“202103 Wi-Fi 6e and 6 GHz Update – Wi-Fi Alliance.” Accessed August 30, 2021. https://www.wi-fi.org/download.php?file=/sites/default/files/private/202103_Wi-Fi_6E_and_6_GHz_Update.pdf.
Rock Radio Scrapbook: from the Archives. Accessed August 30, 2021. https://rockradioscrapbook.ca/arc-jan22.html.
“Welcome to Forgotten Buffalo.” WKBW Radio 1520 AM Buffalo, New York 50,000 Watts. Accessed August 30, 2021. http://www.forgottenbuffalo.com/wkbwradio/kbgoeskaboomwkbw.html.
