AirOS – Software Release: v8.5.4/v6.1.7

airOS – Software Release: v8.5.4/v6.1.7

Ubiquiti released airOS v8.5.4 for airMAX AC and airOS v6.1.7 for airMAX M. Over the past couple of months, the whole airMAX team and community beta testers have put in a lot of time and effort to make sure these releases and all their great new features and fixes are ready to go. Without further ado, let’s dive right in and take a look at some of the most important ones:

New Flexible Mode

Prior to this release, airOS had both flexible and fixed modes. These terms refer to how the capacity of the wireless link is allocated; dynamically, as in flexible mode, or statically, as in fixed frame mode. With the former, the percentage of the link that is used for uplink data and that which is used for downlink data are adjusted dynamically depending on the traffic mix at that time. In fixed mode, as you might expect, this downlink to uplink ratio is fixed, such as 75/25.

These new releases add a new mode, known as New Flexible Mode. To find it, go to Wireless configuration and click the drop down for TDD Framing on an airOS device configured to be a PtMP AP. As shown below, it’s listed as Flexible (NEW) just below the existing Flexible mode.

This new mode is supported on both airMAX AC and airMAX M, as long as they are using airOS v8.5.4 and v6.1.7 respectively. The old mode- “Flexible (legacy)” isn’t going away in this release, so existing networks that may want to wait but still use the other new features in these releases can do so without any issues. However, there are a few neat advantages to the new mode:

  1. ReSE compatibility – In airOS v8.5.1 and v6.1.6, UBNT released ReSE (Receive Signal Enhancement), a feature that improved the performance of many networks and helped them ignore interference. Due to its internal operation, this feature didn’t work with Flexible (legacy) mode. But, it does work with the new Flexible mode, bringing all of the key advantages of ReSE to networks that don’t want to use fixed TDD Framing. Check out the release blog for those versions of airOS to see some more detail on ReSE and how it performs.
  2. Better performance – Even without using ReSE, there have been cases where the new Flexible mode outperforms the old one by a good amount. The testing performed below on a real-world link shows a transmit throughput performance increase of roughly 35%:
  3. Latest work – Throughout the past year, UBNT have spent a lot of time and effort improving their fixed frame link mode. The new Flexible mode is built on the same foundation, meaning it uses the most modern underlying systems throughout both the OS and hardware. This gives the new Flexible mode a solid base to support new future features, like how they were able to introduce ReSE for fixed frame links with just an on switch from the user’s perspective.
  4. PtMP and PTP – Much like with fixed frame mode, you can create PTP links that use the new Flexible mode easily by configuring one end of the link as a PtMP AP and connecting only a single Station (or CPE) to it. This means high-performance PTP links with flexible TDD framing, plus the great addition of the enhanced link robustness provided by ReSE.
  5. Link Range – In Flexible (legacy) mode, the link distance was limited to around 22 km for 20, 40 and 80 MHz channel bandwidths. However with the new Flexible mode, your network can support Stations up to 75 km away, giving your more flexibility and design options to use.

All in all, the new Flexible mode is another tool in your kit as a WISP. The aim is to make it as simple as possible to decide which mode to use for your network, and with the new Flexible mode they are one step closer; rather than choosing from many different modes, you can stick to fixed frame and the new Flexible mode, then just choose whether or not you need to use GPS Sync on that particular link or AP. This leads us nicely into a question that will be asked as well.

Are the old modes going away?

The current Flexible (legacy) and PTP modes aren’t going away any time soon, and there will be several releases available, with airOS v8.5.4 and v6.1.7 being the first, that support all of these modes. However, to simplify the operation of airMAX in the future, these legacy modes will eventually go away. The release where this occurs will be clearly marked and the change will be communicated to the community. Not only does this make airMAX simpler to use, but it lets us create more new features and shorten the time to create them for each mode as well.

Note that as of today, the new Flexible mode has the same client number limit as fixed frame mode; 60 clients for 5AC and 50 clients for 2AC. An airMAX AC AP is also required to use it.

GPS Sync in 10 MHz

On to the next feature with some improved flexibility for GPS Sync networks. Until now airMAX AC has supported 40 and 20 MHz channel bandwidths with GPS Sync; but especially for 2.4 GHz networks which are now able to use GPS Sync thanks to the Rocket 2AC PRISM, 10 MHz channel bandwidths have been a popular choice. As of airOS v8.5.4 and v6.1.7, for both AC and mixed mode networks GPS Sync will now operate with a 10 MHz channel bandwidth, configured for:

  • 8ms frame duration, 67/33 downlink/uplink ratio
  • 10ms frame duration, 67/33 downlink/uplink ratio

This feature gives GPS Sync network operators some additional options to fit high-performance networks into crowded spectrum, especially in the 2.4 GHz band but also in 5 GHz. It’s been an often-requested feature on the community forum, so they're glad to be able to deliver it and respond to your feedback with the features you’ve requested.

UI Updates

They’ve packed quite a few UI updates into these releases too, so we’ll just cover two of the main ones. First, they’ve added support for Daylight Saving Time, as requested by the community. This feature makes sure your airMAX devices keep their system clocks up to date throughout the year. Second, they’ve updated the airOS login screen to simplify things and make it easier to discover and access some of the supporting tools like Link, UNMS and UCRM:

One other update is the return of the SSID to the Link view in the airOS dashboard. This change is a direct result of your community feedback, as this was highlighted from the previous release. Thanks to everyone in the community who makes their voices heard on each and every release.

Bug Fixes

No release would be complete without bug fixes, and thanks to both feedback from the community and their own internal testing they’ve identified and fixed several small annoyances from the previous version of airOS, making airOS v8.5.4 and v6.1.7 better than ever. Among these are making the DHCPv6 Unique ID permanent, fixing some special character display issues, and making sure station sorting works properly. Again, many of these are a result of your feedback on the community, and we would like to thank you all for making your voices heard.

For a full list of the changes in airOS v8.5.4 and v6.1.7, please check out the accompanying release notes for each of them in the Downloads section on We look forward to seeing your feedback on these new releases and how they’ve helped you and your network.

Blog post by Ubiquiti