When 802.11 got the ax…

Welcome to 2018! Yes I know it’s February 2nd, but it was nice to take some time away the last couple months to enjoy the holidays and a much needed vacation. To start my blogging year, I want to tackle the first of many hot button topics this year. 802.11ax.

We’ve all heard that wireless is about to get a LOT faster with the upcoming release of 802.11ax. Now that we’re in 2018, the time is here for enterprise class vendors to start releasing their shiny new products and all of the marketing FUD that comes with it. I wanted to take a few minutes to briefly talk about some of the key topics. WARNING: I am not an expert by any means on this, and much of this information comes from a presentation by Eldad Perahia last year at the 2017 WLAN Professionals conference in Phoenix, AZ. You can find that video here.

These are the pieces I think are most intriguing, but keep in mind nothing is finalized yet with regards to release dates. Unfortunately, much like 11ac, it looks like most vendors will release wave 1 and wave 2 features for 11ax as well.

#1 Battery Life Improvements

Within 11ax there has been an effort to improve battery life in devices by introducing a negotiation between the AP and client that allows for a scheduling of transmissions to occur between the AP and sleeping stations. This is known as Target Wake Time (TWT). It is borrowed from ideas developed for 11ah that helped with battery life for super low power devices. While any amount of increased sleeping will add up, the thought that clients could sleep for very long times seems a bit outlandish when it comes to most wireless devices. I’m skeptical as to how much this will really improve the average wireless client’s battery life, as most devices like laptops and tablets have large batteries already. I suspect this will mean the addition of a handful of minutes, more so than hours. IoT devices will benefit the most from this, but then again I see them fitting in better within the new 11ah territory.

#2 Network Efficiency Improvements

Within the 802.11 standard, CSMA/CA mandated only 1 station was allowed to transmit at a time. Therefore, if you had a super dense AP deployment you could effectively be blocking a large number of AP & clients from communicating since they were close enough that multiple AP could decode the 802.11 preamble and have to backoff. So how does 11ax help with this? It’s important to note that 11ax does not bring us any additional spectrum space, but there are improvements introduced to the usage of what we have presently. Introducing multi user OFDM, known as OFDMA. Within 11ax, we will have the ability to slice a single 20 MHz channel into multiple chunks of spectrum, each as little as 2 MHz wide. The 2 MHz channel width will be capable of throughput up to 12 Mbps for transmissions. Based on the knowledge that more than 80% of frames transmitted on the wireless medium are under 256 bytes, the 12 Mbps data rate should provide plenty of throughput for the smaller frame sizes. Also, no longer does a single client dominate the entire channel, but it allows up to 9 additional stations (assuming 2 MHz channel widths) to communicate within the same time period, greatly reducing the time the medium is occupied. In high density networks this will be a huge help in improving network efficiency.

#3 Data Rate Additions

Introducing 1024 QAM. This is one of my least favorite additions of the 11ax amendment. While I’m all in favor of improvements and new developments, I typically like to see them be things that can actually be used, In reality with current device sensitivity and the signal strength required to be able to hit the marks in the 1024 QAM constellation, you’ll basically need to strap an AP to every person in your network and then glue their device to the AP. Just remember use the outer portion of the AP since you have the blackhole in the very center of the omnidirectional antenna 😉

#4 Flying Colors

A new feature has been created called OBSS (overlapping basic service set), or my preferred name, BSS Coloring. This feature will help us talk over our neighbors if you will, by color coding each transmission within the same frequency space. Thus you could have client 1 speaking on Ch.36-blue and client 2 using Ch.36-purple. While this might decrease the SINR for client transmissions, the improved efficiency by allowing multiple client transmissions within the same channel helps reduce co-channel contention. It’s important to note though that for this to occur all stations Tx or Rx must be 11ax stations.

#4 Channel Numbers

While this isn’t an improvement, I thought I’d mention it anyway. I know everyone hates learning new channel numbers. Fortunately, It looks like we get to keep the current channel designators we have based on the 20MHz channel widths across the board. I knew you would agree with me that I saved the best knowledge bite for last.  🙂

Hopefully this was a good primer on 802.11ax and the pieces of the amendment I think will most benefit everyone, especially those with HD & VHD networks. While each vendor will still have unique things they implement based upon their interpretation of the amendment, these are the core values I find most interesting. Be on the lookout for 11ax access points coming soon to a market near you!

As always any comments or questions are appreciated.

-Scott

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