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Benefits of Upgrading to 802.11ax and Should You Do It

Benefits of 802.11ax

OFDMA
Orthogonal Frequency Division Multiple Access - this is the new modulation technique introduced with 802.11ax and replaces OFDM that has been around since 802.11a. This is the same modulation used by cell phone carriers to transmit data to and from your cell phone. This modulation assigns each client resources units (RU) that can dynamically change based on the application needs of the client. Without going too in depth, I’ll use an analogy to show the difference between OFDM and OFDMA – OFDM would be the equivalent to driving a country road and getting to a one lane bridge and OFDMA would equate to a multi-lane interstate. When driving the country road, it doesn’t matter what you drive or how fast you go, if it isn’t your turn to cross the bridge, you aren’t moving. In OFDM, only one device can transmit at a time. If 2 vehicles crossed that bridge at the same time, they have a collision and then all the cars waiting are now affected. The same is true for OFDM. If two clients try to transmit at the same time, such as a hidden node, the frames from the clients will be corrupt and will have to retransmit. Constant retransmissions eat away available airtime for other clients and therefore slow your wireless network down. In contrast, OFDMA is like a huge multi-lane interstate where you have lanes for the fast cars and the slow cars. You even have enough lanes for the wide load trucks to occupy 2 lanes without impacting the flow of traffic. OFDMA lets multiple clients send and receive data at the same time. This is done by breaking one channel into a lot of subchannels or resource units (RU). The AP can then dynamically assign RUs to each client based on their needs. This is a much more efficient way to transfer data over the air and aggregate throughput in a wireless network will increase greatly over an 802.11ac network.

Supports 2.4ghz band
A lot has been said about the wasteland that the 2.4ghz band has become. Its available 3 non-overlapping channels (4 in Europe) are nothing compared to the 24 (25 if you count channel 144 that is available to 802.11ac devices) non-overlapping channels in the 5ghz band. In recent years with IoT, the flood of cheap 2.4ghz devices has made a previously congested band almost unusable in most environments where client density is high. Since 802.11ax divides the channel into smaller subchannels, it will support greater client density, but that only happens with 802.11ax compatible clients. If non-802.11ax clients are still on the network, they will still operate like the one lane bridge scenario above and slow down the faster 802.11ax clients.

MU-MIMO on uplink and downlink
802.11ac Wave 2 introduced MU-MIMO (Multiuser User MIMO) which allowed the AP to use individual radio chains to transmit to individual clients. However, the clients still transmitted to the AP one at a time. It also has a lot of overhead that uses a lot of airtime that the devices need to communicate. With 802.11ax, MU-MIMO will now be able to operate in uplink and downlink, which is a more efficient use of airtime and a more efficient use of the overhead, that is created by the sounding frames, when the AP groups clients together for MU-MIMO.

1024 QAM
Everyone remembers the hype around the speed of 802.11ac. That is partly because of the ability of the coding to cram more bits into a symbol. 802.11ac introduced 256 QAM which coded 8 bits into one symbol. 1024 QAM will code 10 bits into one symbol, which creates 25% more capacity! The QAM scheme the device gets is directly related to signal to noise ratio (SNR). SNR is the difference between the received signal strength indicator (RSSI) and the noise floor of the environment. The higher the SNR, the faster your data is transferred, thanks to the coding scheme being used. That is why being close to the AP is always better!

Schedule based airtime
In all previous versions of Wi-Fi, the devices ran the show. They would contend with each other for the wireless medium and once they won the transmit opportunity (TxOp), they would tell the AP how long they would use it. The 802.11 standard created guidelines for how this is to be done and controlled, but not all wireless chipset manufacturers follow the standard completely and could at times take advantage of it. 802.11ax will allow the access point to control the traffic and decide when the devices can transmit. This makes more efficient use of the airtime and it also lets the client device know when to sleep so it can save battery. Previously, the device would sleep and tell the AP when it will wake up (DTIM interval), which means the AP would queue traffic to this client and send it once the interval expired.

Should you upgrade your access points?

Do you have 802.11ax client devices?
Although these are in development and some may already be out, I’m willing to bet the answer to this is no. As a matter of fact, it is likely that you still don’t have all 802.11ac clients on your wireless network. Besides the benefits of faster hardware, you will NOT see any benefits from an 802.11ax access point without devices that support 802.11ax. My advice is to always upgrade your clients, as they are the weakest link in your network.

What does your current model AP support?
802.11n only - 
If this is the case, and it makes sense financially to do it, I would recommend upgrading to 802.11ax, if they are available from your preferred manufacturer. You will be ahead of the curve and have the latest and greatest hardware. Like above, you will not see any benefits until you upgrade your clients, but this is the scenario that makes the most sense to upgrade to 802.11ax access points.
If 802.11ax access points are not available, I would not wait on them. The benefits of switching to an 802.11ac access point from an 802.11n is surprisingly high, even if you only have 802.11n clients.

802.11ac Wave 1 - 
This will depend on when you purchased these access points. These access points have been out for at least 5 years, so if you have had these for a few years and your AP refresh cycle is coming up, you may want to look at upgrading to 802.11ax access points. If it will be 3-5 years before you can refresh your devices to 802.11ax, you may want to look at getting 802.11ac Wave 2 access points, if it saves money, so you can focus on upgrading the clients.

802.11ac Wave 2 - 
First of all, there is no such thing as “wave 2.” This is not specified in the 802.11ac amendment, but is instead a staged approach by manufacturers to introduce the features in 802.11ac, most likely to sell more hardware. All the features in wave 2 are in the 802.11ac amendment specified by the IEEE. Most of these access points have been out for 2-3 years. If you just recently purchased wave 2 access points, I would not recommend upgrading to 802.11ax access points. Once again, look at your clients – are they 802.11ac, let alone wave 2?

Summary
Clients, clients, clients…unless you have clients that support the improvements introduced by your AP, you will not reap the benefits. From my experience working with schools, colleges, enterprise and manufacturing, we tend to focus on getting the latest and greatest technology, even when it is not practical. Whether it is school systems trying to roll out a 1:1 initiative while still using single band laptops or manufacturing plants installing 802.11ac wave 2 access points, but still using 802.11b bar code scanners, the clients are the most important part of a wireless network and should be addressed first. The manufacturing plant would benefit exponentially more from upgrading their barcode scanners to 5ghz 802.11n devices than they will from wave 2 access points and keeping the 802.11b devices. The school system would see a drastic improvement if they replaced the single band clients with dual band clients.

802.11ax is an amazing improvement to wireless and will make wireless networks much more efficient and faster, BUT only when the devices support it.

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