If you consider purchasing the DJI Mavic 2 Pro or Mavic 2 Zoom you’d definitely hear of new OcuSync 2.0 FPV transmissions technology. But what is this OcuSync? In this article we break it down to you.
A Little History
OcuSync was first introduced with the Mavic Pro and it’s part of the Lightbridge family and is a wireless transmission system that offers low latency HD wireless video signal and control signal and allows you to transmit this up to long range. The original Mavic Pro was able to transmit HD 720p up to 4.3 miles in total. Transmitting on 2.4 gigahertz OcuSync could transmit both 720p and 1080p video. 1080p mode was only for short range and when you selected that in auto it would automatically drop down to 720p once the signal started to degrade one.
Of the big benefits of OcuSync was its fairly low latency for a digital system. Whilst nowhere near as low as analog it was between 160 and 170 milliseconds. One of the big benefits of it was that it allowed you to have up to 4 devices connected in total and DJI allow you to use either 2 remote controllers and 2 goggles or three remotes on one set of goggles. This was something new that we hadn’t heard of at the time.
Shortly after the Mavic Pro DJI released their new FPV Goggles. These were able to receive the OcuSync signal directly and they offered low latency wireless FPV. They supported a number of aircraft features that included head tracking camera control and aircraft settings. DJI also introduced a new smooth mode which gave 720p at 60 frames a second live viewing. The advantage of this mode is that it had a lower latency than the normal channel modes and it was able to give you FPV latency down to a 110 milliseconds. One of the downsides of this mode though was the limited recording on the aircraft to 1080p at 60 frames a second as well. So you could record in 4K if you used the standard transmission modes with the higher latency but if you wanted to get the lowest latency out of the Mavic Pro whilst using the goggles you had to use this new smooth mode.
Later DJI updated the Mavic Pro to the Mavic Pro Platinum. However there was no changes to the OcuSync transmission system on this model. It was exactly the same system which still worked with the DJI goggles as it did before and there was no changes whatsoever.
Shortly after the Mavic Pro Platinum DJI released the Goggles Racing Edition alongside the OcuSync Air System. This was designed for DIY use in FPV race drones as well as fixed-wing aircraft and it was a new updated version of the OcuSync system, sort of label it OcuSync 1.5. It now added dual band so it would work on both 2.4 and 5 gigahertz. The new version had lower latency than the original OcuSync on the DJI Mavic Pro and it was specifically designed for FPV flying. It had a maximum resolution of 1280 x 960 with the latency as low as 50 milliseconds if you dropped the resolution down to 480p. Another new feature with this system was the ability to automatically switch between bands. So change between 2.4 and 5 gigahertz in flight to get the best possible signal became a reality.
The next aircraft to use OcuSync was the new Phantom 4 Pro v2.0. The original DJI Phantom 4 Pro still used Lightbridge but the P4 Pro v2.0 they shifted to the newer OcuSync. Again, this was more of a hybrid system: it wasn’t the same as the Mavic Pro but it also wasn’t quite the same as the goggles either. It had the same dual band as the goggles OcuSync Air System but it was not able to change band automatically in flight. So whilst it could use 2.4 or 5 gigahertz you had to manually select it. The system was still able to transmit up to 1080p and it had a range of approximately 4.3 miles. It did have a latency of between 160 and 220 milliseconds and the reason for that being so wide was it depended if you were using a smartphone or you were using the plus RC from DJI. The lowest latency came when you were using the plus RC which was between 160 and 180 milliseconds and the 220 milliseconds figure was if you were using an Android device. Like the original OcuSync it still had the option for 1080p and it would still drop down to 720p when the signal became weak.
The brand new DJI Mavic 2 Pro drone uses something called OcuSync 2.0. DJI is pretty much combined all of the previous versions of OcuSync into one system and added some improvements as well. The new system will give up to 1080p in 5 miles, it has dual band 2.4 and 5 gigahertz with automatic band switching in flight. So it will automatically jump between the two modes to give you the best possible signal. It has a new lower latency than we have seen on any the RTF craft before with to 130 milliseconds and it has the ability to separate the control and video link frequency onto different bands. Another advantage to OcuSync overall is that its firmware can be updated.
Looking at OcuSync in a lot more detail it is basically an identical system to DJI Lightbridge in the sense that it is an OFDM video carrier which is surrounded by FHSS control signals. If you look at the top picture you have an OFDM carrier in the center. This is that very large mass of lots of little carriers you can see in the middle. The way the OFDM works on this drone is when you first turn it on it will look for a clear channel and the video will settle on that channel and stay there throughout the flight. The only time that video carrier will shift is:
- if it picks up interference or
- if you manually tell it to change channel.
However as long as it’s working in normal environment it will pick a single channel on startup and that’s where it will stay for the entire flight until you tune the aircraft off.
Around this you would then have an FHSS control signal now. The way FHSS works is you have constant packets of data jumping across the entire band. This bottom picture is a spectrum representation of this and the blue peaks are basically the historic positions of where the carrier has been. Tt is jumping at such a high frequency it is often very difficult to see.
So what each of these Peaks is, is a position with the carrier has jumped to and it is constantly jumping between these positions.It’s not doing it in order it often does it randomly. So what you will have is it jumping from the first one to the eighth to the third to the tenth and so forth. And when you look at it on a spectrum what you end up seeing is this representation of lots and lots of peaks. Each of those Peaks is a position with the carrier it has been and it will jump back to at some point in the future but it is not in that position when you show it like this.
The way both OcuSync and Lightbridge are it is these two systems combined into one. If we look at an actual OcuSync trace you can still see the OFDM mass in the center and this is the main video carrier that is carrying your HD video signal from your aircraft back to your remote controller. The blue peaks you can see all around it are the FHSS signals jumping round for your control link. The light blue one here is one of the current ones that it’s been jumped on to and the darker blue are the historic ones where it’s been in the past
Something to note: when you look at this is you can also see that it jumps over the OFDM carrier as well. So the FHSS is constantly switching frequency at a high rate and it even jumps over the main channel that your video is on because it is jumping so fast it doesn’t matter that it jumps over the top. Because even if that information isn’t received it’s already jumped on to the next position and that packet will be picked up by your remote controller or your drone.
Let’s Comparing OcuSync to Lightbridge on a spectrum. This is OcuSync:
And this is Lightbridge signal:
As you can see they are very very similar. You still have the same OFDM masses with the FHSS control signal jumping around it. As I mentioned previousl, on the top on the big red mass is your OFDM with your light blues and dark blues being the FHSS. On the Lightbridge at the bottom the same red mass is the OFDM with the blues with the FHSS has been and the pink ones the current position it’s jumping on to.
So when you look at these two systems from a radio point of view they are very very similar and virtually identical.
So what is the actual difference between them? Well, the basics are as follows:
Lightbridge is a combination of custom hardware and software. It’s expensive to build because it was originally based on FPGAs. However, later DJI moved over to using custom silicon.Yet, because it is a combination of hardware and software it is expensive to make and it also has limited upgrade ability. This is why when you look at things like the original Phantom 3 and the Inspire 1 which were compatible with each other and then move to the DJI Inspire 2 and they aren’t compatible. That was because there was hardware differences and you couldn’t use one with the other.
OcuSync on the other hand is more of a software based system and more of an SDR. It’s able to work on generic off-the-shelf hardware so eisting Wi-Fi hardware, for instance, is able to use the OcuSync system. It allows DJI to keep the hardware costs down because they’re not having to make custom hardware or expensive FPGAs. This allows them to use a far more compact packaging because many of the SOC’s and the processes we use in all devices these days, like in smartphones and in these drones, already have radio hardware onboard that is designed for Wi-Fi. So DJI are able to leverage existing hardware to be able to get the same type of system that they originally designed with Lightbridge.
Benefits of OcuSync over Lightbridge
Because OcuSync is a software base it means DJI can upgrade it. There will always be hardware limitations of course. But if we look at the original DJI goggles, they will be updating nuts to support the new OcuSync 2.0 that came with the Mavic 2 Pro & Zoom because they can be compatiable on the same frequency. It will only work on 2.4 gigahertz because there isn’t a 5 gigahertz radio. However, if this was Lightbridge they wouldn’t have even been able to do that because Lightbridge is a combination of hardware and software for the whole transmission system and it just wouldn’t have been compatible. However, because OcuSync is an SDR and it is software, it means within reason and as long as the processors are powerful enough to support it they can upgrade existing systems to be compatible with the newer ones.
The basics are between the two is that they are very very similar systems. OcuSync allows DJI to do what they did with Lightbridge on basically existing off-the-shelf hardware. It allows them to do it better and cheaper in smaller packaging and that’s why the Lightbridge system has been sort of kept for the larger and more expensive drones whereas OcuSync has been used on the lower models but it’s giving virtually identical performance in the end.
If I’m honest I think DJ I will pretty much move over to OcuSync on every system as time moves on. Whilst the DJI Inspire 2 currently does still use Lightbridge (because there are a few little benefits of this transmitting system) I would expect any future aircraft to probably move over to using OcuSync.
Here’s the final small chart of devices that use different OcuSync versions and are compatible with one another:
|Mavic Pro||2.4Ghz||OcuSync||DJI Goggles||DJI Goggles Race Edition||Original Remote|
|OcuSync Air System||2.4/5Ghz||OcuSync||DJI Goggles||DJI Goggles Race Edition||Original Remote|
|Phantom 4 Pro v2.0||2.4/5Ghz||OcuSync||DJI Goggles||DJI Goggles Race Edition|
|Mavic 2 Pro & Zoom||2.4/5Ghz||OcuSync 2.0||DJI Goggles||DJI Goggles Race Edition||Original Remote|
If we start the top you’ve got the DJI Mavic Pro. It works only on the 2.4 gigahertz band and it uses the original OcuSync system. It will work with the DJI Goggles White Edition the Goggles Race Edition as well as the original Mavic Pro remote.
Next you see the OcuSync Air System and that works on the dual band which is 2.4Ghz and 5 gigahertz and is compatible with the same three items as well.
If we look at the DJI Phantom 4 Pro version 2.0 it is dual band OcuSync. However, as of today it only works with the White Edition Goggles and the Goggles RE.
Finally, at the bottom you have the new DJI Mavic Pro 2. Again, it has dual band but it does use this new OcuSync 2.0 and it will be compatible with both the Goggles the Goggles RE and the original Mavic Pro remote all after a firmware update.
In this chart I’ve got the Goggles or the device on the left with the systems it works with on the right showing you what band it will work on so:
|DJI Goggles||2.4Ghz Only||OcuSync||Mavic 2||Mavic||OcuSync Air System|
|DJI Goggles RE||2.4/5Ghz||OcuSync||Mavic 2||Mavic||OcuSync Air System|
|Mavic RC||2.4Ghz Mode Only||OcuSync||Mavic 2||Mavic||OcuSync Air System|
|Mavic 2 RC||2.4/5Ghz||OcuSync 2.0||Mavic 2|
Be aware, that Mavic 2 will be compatible with the Goggles&Goggles RE and Mavic remote only after firmware update (maybe it’s already happened as you reading this guide).
Finally, I just wanted to talk a little bit of why the DJI Mavic Air uses Wi-Fi and the Mavic Pro uses OcuSync. Whilst I’ve mentioned OcuSync uses off-the-shelf hardware it does still need a lot of processing. That processing creates heat and you have to have the space to add that processing and get rid of that heat when it’s in use. And the basics are: whilst you can still package OcuSync in an aircraft the size of the Mavic Pro getting that into a system like the Mavic Air is probably a bit too much of an ask. If anyone has got the OcuSync a system you will know how much heat that system produces and that heat has to go somewhere. Basically with an aircraft the size of the Mavic Air they pretty much hit the limitation of what they could squeeze into a package of that size.
That is it for this guide I hope I’ve been able to explain OcuSync 2.0 a little bit in detail for you.