I bet you didn’t think you’d see a post about Ant+ vs Bluetooth going into 2019! But nevertheless here we are. This is a topic that bugs me any time I see it in a forum or comment section. On the one hand you have supporters of Ant+ who have been quietly using sensors for many years. On the other you have people who’ve heard of Bluetooth and assume it’s better. Neither answer is 100% right, of course, but for normal use in my opinion there definitely is a correct answer. This is borne out of experience with lots of sensors and devices so bear with me. Your answer might well be different, but more than likely that would only be due to a device forcing your hand.
Ant is an open standard just like Bluetooth. It’s certainly had a rocky road to call it open, and some parts are still Garmin only but they are getting there gradually. I like to think that sometimes the cost of opening something up is more than it’s worth at the time which leads to things like running dynamics and cycling dynamics being closed initially. When demand is there Garmin do eventually open these up. Usually. Eventually.
Broadcast is the mode Ant works in. This means that a sensor transmits into the void and anyone with an antenna can read the signal. This is like normal TV or radio signals. This is great from a usability perspective because everything just works. Alternative options include unicast which is like a one to one phone call and multicast which is kind of like pay TV where you only get access if you have the key. Broadcast is a nice thing too because it doesn’t have authentication or encryption (although there’s no reason they couldn’t encrypt). This keeps processing to a minimum and therefore latency is lower and power consumption is kept down. Importantly though, lower processing means it’s easier to support more devices (or channels) at once. For gadget geeks this is great because you know you can use your power meter, light network, aero, DI2, cadence, HR, speed and tyre pressure sensors all at the same time. And you can do that to as many head units and watches as you like thanks to that broadcast capability.
Ant+ also has very mature device profiles which have long been standardised. Running, power, speed, cadence, pretty much everything is covered including remote displays and temperature sensors. A device profile is a very simple thing. It just explains what data will be sent and in what format. An HR sensor for instance might send the following (each line represents one transmission):
As the receiver, if I know this is an HR sensor then I know that’s the bpm of a heart. I nearly said human heart there for a second, but Polar famously have HR straps for race horses too! If we have a dual power meter we may see something like the below:
This example is of course the Vector 3 (I don’t know whether this is the format). As you can see the right pedal drops out a little but it doesn’t matter because the received data can still be used. Here we specify which pedal and a wattage. I’m sure there are more numbers mixed in there too but this shows the general idea of a sports profile.
Bluetooth is of course an open standard too. It’s a much broader standard though because Bluetooth isn’t sensor specific. In fact, Bluetooth in the old days was horrible for sensors because it kept the channel open all the time and sucked power or it killed the connection and took ages to reconnect. The standard evolved though, and some of the requirements of sensors were added in such as low energy modes.
Bluetooth has traditionally always been a unicast technology. Its roots were as a cable replacement technology to replace USB and similar standards. As such security was of highest concern. Pairing devices was originally a royal pain and you had to provide the pin number and verify. Now it’s sufficient to just say you trust that’s the right sensor and you’re done. The underlying security is still there though. Each device has to pair and trust the other, and during this pairing a key is generated such that only the two devices know it. No other device can then eavesdrop the signal. This is ACE for pro cyclists who don’t want their data revealed/changed, or their gears changed on a mountain stage. For this reason a pro athlete may have genuine concerns about Ant+ and the reliability of data being received. It would be trivial to spoof an Ant+ ID and transmit bad data. Imagine seeing your HR peaking on a climb and slowing down to avoid problems only to find it wasn’t your actual HR value! I don’t have this concern. If someone messes with my data I’d be mildly miffed at most. I suspect you’re in this category too if you’re reading this. It’s worth knowing though.
I said traditionally because Bluetooth has had the ability to multicast for a while now (ages in fact). It’s technically capable of having sensors talk to multiple devices. I know, I’ve seen it working on the Polar H10. Most recent devices even have hardware that supports this. Polar H10 is the only one I’m aware of that actually implements the software support though, and even then it only supports two devices. Great, so we can have a cycling head unit (if it supports BTLE) and a watch at the same time. We can’t also do Zwift though, that would be three. We also need to re-pair to use the strap with another different device. That means each time I take a different device out I have to dance the BTLE dance to make sure I have all the sensors ready and raring to go. Really I just want to go for a run.
Zwift is a great example here too. With Bluetooth I have to choose between head unit or computer. Personally I like to have both running so I see power numbers on my bar while the screen also does Zwift. Maybe that’s OCD.
And sports profiles. Oh sports profiles. They are getting there. Still. Bluetooth just doesn’t have the focus of Ant+ here and so it’s a bit of a mess. Power meters may transmit single or dual power depending on the manufacturer implementation. Some of them transmit single power from each pedal. And that’s all good, except a lot of Bluetooth devices have a very low limit on the number of devices they can talk to. Apple TV is a constant headache for Zwifters, and Suunto watches and power pedals are generally not friends.
It’s a bit of a frustrating one here because ultimately you’ll get what you’re given. Unless you have a Garmin which supports both you’re probably limited to one or the other. What I can say though is in every single instance where there’s a choice you should choose Ant+. Unless you’re worried about security, then go Bluetooth. Ant+ profiles just work. I’ve never hit a limit on number of devices with Ant+. More importantly I’ve never had to choose devices with Ant+ I just connect as many watches and head units as I want. And I want at least two bike computers and a watch, just in case. I’ve said a few times that I’d love for my Vantage V to be my daily watch as I prefer it to the Fenix. Honestly though it’s just too much effort with Bluetooth connectivity and pairing so I end up using wrist HR on the Polar which leads to bad data which leads to not using the watch. I can’t record my Zwift workout into the Polar ecosystem because Bluetooth is busy talking to the computer. This means Recovery Pro is worthless immediately because it’s missing data. And that means the main selling point of the Polar is actually missing. I’ve just started running in Zwift too, so Polar will be missing my treadmill workouts going forwards too. With Ant+ Garmin and Zwift get all of the data. And Garmin also allow syncing data into Connect too.
Don’t get me wrong, Polar are doing more than most to make Bluetooth work. I just wish they’d add Ant+ support so I could fully utilise my watch.