GPS Sync: Taking airMAX Further

by Ubiquiti Employee ‎06-16-2017 04:23 AM - edited ‎06-16-2017 10:06 AM



Today, we released GPS Sync for airMAX AC in airOS v8.3.


This is a powerful feature for many networks worldwide, and it’s a very exciting addition to the platform. Starting today, airMAX is more powerful than ever for serious, world-class wireless deployments from the smallest sector to nationwide service provider networks - and this is just the beginning.


For those familiar with the concept of GPS Sync, I’ll get right to the point: not only does GPS Sync in airMAX AC provide all the benefits you would expect, but airMAX AC provides over 90% higher throughput with real-world TCP traffic compared to competing systems.


Test Configuration #1


  • 40 MHz channel bandwidth
  • 75/25 downlink uplink ratio



Downlink TCP Throughput

airMAX AC GPS Sync

240 Mbps


124 Mbps



 We have also added advanced traffic optimizations to improve performance considerably over other systems under the same wireless conditions, as you can see in the next test.


Test Configuration #2


  • 40 MHz channel bandwidth
  • 75/25 downlink uplink ratio
  • 6x wireless link rate (fixed)



Downlink TCP Throughput

airMAX AC GPS Sync

150 Mbps


124 Mbps


In this test, both products claimed the same wireless data rate, but real-world TCP traffic shows that GPS Sync in airMAX AC stands above in performance with over 20% higher throughput. Performance will also continue to grow in the future on airMAX AC.


Better still, building on this is an airOS release allowing M-series CPEs to synchronize with AC APs, planned for release in a few months. Replace an M-series AP with an AC AP (5 or 2.4 GHz) and get GPS Sync, PRISM filtering, AC processing power and other improvements.


This way, not only will your M-series CPEs see highly-improved performance, but with an AC AP deployed you also have a solid upgrade path to AC CPEs when you need to boost your performance further still to keep up with your customer’s data demands. Nothing else needed.


Here are a few quotes from network operators who have been using GPS Sync in airMAX AC on their live production networks, serving their real customers:


"If you haven’t tried GPS sync with AC Prism radios, I HIGHLY suggest it.  We have a number of them operating at this same site with great luck."
— Tony Pierro, Wireless Internet Services, Inc.


"So far the results of tests of the fixed frame / GPS sync features have been beyond our expectations. The biggest benefit I have noticed so far is that latency is much more consistent on heavily loaded links than it had been on normal airMAX. This will be a great benefit for VoIP. Can’t wait to see how well channel re-use works as we turn this up on more APs and towers."

— Randy Cosby, Infowest


"Ubiquiti GPS sync transcended our network to an entirely new level. After activating GPS sync we are now seeing perfect MOS scores on our VoIP calls, and over 90 Mbps capacity per sector."

— Joe Glende, Hiawatha Broadband Communications, Inc.


Better yet, check out a couple of the stories that have been posted so far on the community. First, 5 times the speed by switching M-series equipment for airMAX AC with GPS Sync. The feedback from a customer who got that speed increase speaks for itself:


Next, an awesome deployment with 4 synchronized HD-90 antennas, operating 12 30-degree sectors with only 4 antennas and 6 channels. Maximum density, maximum ROI, and providing higher levels of service to real customers than before with massively improved performance:





Now, for those less familiar with it, here is an overview of the problems GPS Sync solves.


In an unsynchronized network, APs on the same channel can interfere with each other when in range of each other’s transmissions. Issues occur when one AP is receiving as another AP is transmitting, disrupting the ability of the receiving AP to decode its wanted transmission. This can be a problem when trying to deploy a dense network, or other co-location scenarios.


GPS Sync fixes this problem by having all APs transmit at the same time, and then receive data from their CPEs at the same time. When this occurs, this type of interference is eliminated, allowing much better network scalability, performance and consistency.


The benefits of GPS Sync range from multiple APs on a single tower to a whole network. As long as frequencies are planned correctly, all APs in a network can be synchronized and operating with a high level of performance. When an AP is synchronized, so are their CPEs.


Finding wireless spectrum that is clear enough to support high speeds is getting more difficult as more networks and interfering devices are turned on worldwide. GPS Sync in airMAX AC is another tool in your toolkit to help you make great connectivity possible everywhere.


Looking at a typical 4 AP deployment, when unsynchronized, 4 channels will be used to prevent interference. But when you add GPS Sync, you can operate with just 2 - this is called frequency reuse because it lets you use half the channels, reusing the same frequency between APs facing away from each other.





But the story gets more interesting when you consider the denser networks being deployed today to support higher speeds and limit interference. For example, this setup with 6 APs needs only 3 channels with GPS Sync, whereas without it 6 would usually be needed.




Think of GPS Sync like a spectrum multiplier. With it, you can make the most of the channels you have available, and fit more customers into less spectrum. When you need to go beyond a single tower, the story is the same: frequency reuse still works in these setups.





Beyond synchronizing APs together, GPS Sync also introduces fixed frame mode. This is required for GPS Sync as the downlink and uplink timings of the APs must be fixed, as opposed to flexible modes (all modes besides fixed frame) where these timings are varied.


Fixed frame mode by itself brings many benefits. Performance is now far more consistent throughout the network, even as the network grows. This ability to keep latency, jitter and throughput more constant is a huge benefit, making high-performance networks easier than ever before.


For more information on GPS Sync in airMAX AC, check out and the GPS Sync Design Guide there for some tips to help you get the maximum performance from your synchronized network.


Stay tuned for more improvements and features coming to airMAX. Please post any questions in the community and remember to tell us your stories.