6 ms·

I think we'd need an RF engineer to answer this more thoroughly, but it's my understanding that there are a lot of materials capable of absorbing the low-energy

by thearn4 10y ago

I think we'd need an RF engineer to answer this more thoroughly, but it's my understanding that there are a lot of materials capable of absorbing the low-energy microwaves that it uses as its transmission medium. Water is a big one, which I think is one reason that having my phone in my back pocket almost always results in a dropped connection to my headphones over the course of working outside for a few hours, compared to my side or front jacket pocket. Too much water in our tissues.

bjt2n3904 10y ago
Hi! RF Engineer here. Bluetooth sucks for a number of reasons, only a few of which actually relate to RF. First, we're bad at naming things. Is it BLE? Bluetooth Smart? BTLE? Bluetooth 4.0, or Bluetooth 4 Low Energy? And what does this have to do with ANT+? This doesn't seem to be a big problem, but it's a sign of deeper problems with the spec. In the long run it makes it very difficult for developers to implement. Bluetooth 2.0 is radically different from BTLE. In 2.0, you had one device which acts like a microphone, and another device which acts like a speaker. This was like getting two people to dance together, it takes a lot of practice to get the joined movements right. If one person stumbles, it all goes down like dominoes. BTLE on the other hand, acts like a (more familiar) client server model. You come up to the bank teller, and have a limited set of operations you can preform (withdraw/deposit money, open/close account). Here's the catch though... the teller is only open for 10 seconds during a 24 hour day, and moves throughout the city. You have to arrive at just the right time, or you have to wait until tomorrow. (This was done for battery saving.) The throughput is also MUCH slower than 2.0, which makes applications like audio out of the question for now. There's also a lot of bureaucratic hype surrounding it. If you look at the release from the BT SIG, it seems very much similar to Java's claim that it runs on a bajillion devices. All in all, BTLE seems to be a solution in search of an IoT related problem, much like Java. So in short, the reason I think it sucks is because it's a very complicated protocol with poor and confusing naming conventions. It sure doesn't help that it keeps getting re-invented! (Although BT5 seems to just be add-ons, finally!) Implementers (both on the HW side and the mobile/desktop side) have a difficult time figuring out how to do things correctly, much less why they need to be done. Things are getting better, but until the next "killer BTLE" application comes out, it's just heart rate monitors and useless iBeacons.
- thearn4 10y ago
  Very informative, thanks! I had no idea the naming conventions were that wonky.
- markrages 10y ago
  Another RF engineer here. What the bipolar junction transistor parent has written is exactly correct. Here is another discussion of Bluetooth vs. Ant as written by someone in my industry (fitness): http://keithhack.blogspot.fr/2016/11/why-hasnt-ant-been-crushed-by-ble.html http://keithhack.blogspot.fr/2016/11/why-hasnt-ant-been-crus...
  - bjt2n3904 10y ago
    Ironically... I'm awful at analog design. I don't deserve this handle :(
- namesbc 10y ago
  FYI, Orion Labs claims that they do audio over Bluetooth LE for their Onyx microphone device.
  - andrey-g 10y ago
    You can do anything over BLE, it's just that it isn't supported natively.
- agumonkey 10y ago
  You worked on BT specs ? BT seems an acute case of design by comittee. It's huge, full of profiles and corners. Nobody implements it really well, everything moves before it's finished. Makes you dream of wires some times.
  - digi_owl 10y ago
    As a user i kinda like the profiles, in particular the OBEX based ones. This because it means i can expect two devices to be able to share files out of the box if both of them have a bluetooth radio. Nothing like that exist for wifi, and i have to set up some client-server scheme to make anything happen.
notalaser 10y ago
As long as you're within the communication range and in whatever your protocol calls a "reasonable" environment (e.g. not underwater), you're OK. The strength of the signals isn't chosen at random, it's chosen so that it allows devices to function well (within the design constraints -- range, environment conditions etc.) -- and so that it meets the power consumption constraints imposed by size, design, cost and technology. tl;dr when someone decided to use a 4 dBm transceiver, they (should have) made a conscious choice about it and would have verified that it's enough. Quite plainly, if the connection drops when it shouldn't, it's either bad software or bad design. Bad software is either the Bluetooth stack (especially in legacy Bluetooth devices; newer stacks tend to fare better) or the firmware that talks to the Bluetooth stack (if it's BLE, this is the safer bet). Bad design on the hardware level is less excusable than it would seem, because a Bluetooth device is not exactly a long-haul wireless link that has to work during the mother of all thunderstorms. There's a wealth of information and modeling tools that help you with this stuff, too. Bad antenna design, bad filtering, bad casing are all common culprits, but I've seen a lot of electronic engineers who wouldn't call themselves RF engineers get it right by just following common sense and doing the math. Sometimes (but even less often), it's not a design problem, it's a manufacturing problem (e.g. PCB antennas that get damaged or don't get etched right. But this is pretty rare. Certainly, the operating environment plays a role, but that's why you consider it while you're designing the whole gizmo. You don't (or shouldn't) get to shrug and say hey, it's not my fault we're basically walking cucumbers. So if a pair of super high-end Bose speakers and a super trendy iPhone keep dropping connection while they're within range, not inside and, respectively, outside a Farady cage or whatever, the reason isn't the black magic that RF design is, it's Bose's and Apple's profit margin. Edit: I do concur with the other fellow who posted here, Bluetooth really is complex and the band it operates in isn't exactly a charm to work with, but frankly, neither of these reasons account for the huge range of devices that are simply badly designed and/or run bad software. There are a lot of Bluetooth devices that work just fine, a lot of other protocols that operate in the 2.4 GHz band and work just fine, a lot of other protocols that operate in similarly noisy bands and work just fine and a lot of protocols that are more complex and work just fine.

by thearn4 10y ago

bjt2n3904 10y ago

Hi! RF Engineer here. Bluetooth sucks for a number of reasons, only a few of which actually relate to RF. First, we're bad at naming things. Is it BLE? Bluetooth Smart? BTLE? Bluetooth 4.0, or Bluetooth 4 Low Energy? And what does this have to do with ANT+? This doesn't seem to be a big problem, but it's a sign of deeper problems with the spec. In the long run it makes it very difficult for developers to implement. Bluetooth 2.0 is radically different from BTLE. In 2.0, you had one device which acts like a microphone, and another device which acts like a speaker. This was like getting two people to dance together, it takes a lot of practice to get the joined movements right. If one person stumbles, it all goes down like dominoes. BTLE on the other hand, acts like a (more familiar) client server model. You come up to the bank teller, and have a limited set of operations you can preform (withdraw/deposit money, open/close account). Here's the catch though... the teller is only open for 10 seconds during a 24 hour day, and moves throughout the city. You have to arrive at just the right time, or you have to wait until tomorrow. (This was done for battery saving.) The throughput is also MUCH slower than 2.0, which makes applications like audio out of the question for now. There's also a lot of bureaucratic hype surrounding it. If you look at the release from the BT SIG, it seems very much similar to Java's claim that it runs on a bajillion devices. All in all, BTLE seems to be a solution in search of an IoT related problem, much like Java. So in short, the reason I think it sucks is because it's a very complicated protocol with poor and confusing naming conventions. It sure doesn't help that it keeps getting re-invented! (Although BT5 seems to just be add-ons, finally!) Implementers (both on the HW side and the mobile/desktop side) have a difficult time figuring out how to do things correctly, much less why they need to be done. Things are getting better, but until the next "killer BTLE" application comes out, it's just heart rate monitors and useless iBeacons.

thearn4 10y ago
Very informative, thanks! I had no idea the naming conventions were that wonky.
markrages 10y ago
Another RF engineer here. What the bipolar junction transistor parent has written is exactly correct. Here is another discussion of Bluetooth vs. Ant as written by someone in my industry (fitness): http://keithhack.blogspot.fr/2016/11/why-hasnt-ant-been-crushed-by-ble.html http://keithhack.blogspot.fr/2016/11/why-hasnt-ant-been-crus...
- bjt2n3904 10y ago
  Ironically... I'm awful at analog design. I don't deserve this handle :(
namesbc 10y ago
FYI, Orion Labs claims that they do audio over Bluetooth LE for their Onyx microphone device.
- andrey-g 10y ago
  You can do anything over BLE, it's just that it isn't supported natively.
agumonkey 10y ago
You worked on BT specs ? BT seems an acute case of design by comittee. It's huge, full of profiles and corners. Nobody implements it really well, everything moves before it's finished. Makes you dream of wires some times.
- digi_owl 10y ago
  As a user i kinda like the profiles, in particular the OBEX based ones. This because it means i can expect two devices to be able to share files out of the box if both of them have a bluetooth radio. Nothing like that exist for wifi, and i have to set up some client-server scheme to make anything happen.

notalaser 10y ago

As long as you're within the communication range and in whatever your protocol calls a "reasonable" environment (e.g. not underwater), you're OK. The strength of the signals isn't chosen at random, it's chosen so that it allows devices to function well (within the design constraints -- range, environment conditions etc.) -- and so that it meets the power consumption constraints imposed by size, design, cost and technology. tl;dr when someone decided to use a 4 dBm transceiver, they (should have) made a conscious choice about it and would have verified that it's enough. Quite plainly, if the connection drops when it shouldn't, it's either bad software or bad design. Bad software is either the Bluetooth stack (especially in legacy Bluetooth devices; newer stacks tend to fare better) or the firmware that talks to the Bluetooth stack (if it's BLE, this is the safer bet). Bad design on the hardware level is less excusable than it would seem, because a Bluetooth device is not exactly a long-haul wireless link that has to work during the mother of all thunderstorms. There's a wealth of information and modeling tools that help you with this stuff, too. Bad antenna design, bad filtering, bad casing are all common culprits, but I've seen a lot of electronic engineers who wouldn't call themselves RF engineers get it right by just following common sense and doing the math. Sometimes (but even less often), it's not a design problem, it's a manufacturing problem (e.g. PCB antennas that get damaged or don't get etched right. But this is pretty rare. Certainly, the operating environment plays a role, but that's why you consider it while you're designing the whole gizmo. You don't (or shouldn't) get to shrug and say hey, it's not my fault we're basically walking cucumbers. So if a pair of super high-end Bose speakers and a super trendy iPhone keep dropping connection while they're within range, not inside and, respectively, outside a Farady cage or whatever, the reason isn't the black magic that RF design is, it's Bose's and Apple's profit margin. Edit: I do concur with the other fellow who posted here, Bluetooth really is complex and the band it operates in isn't exactly a charm to work with, but frankly, neither of these reasons account for the huge range of devices that are simply badly designed and/or run bad software. There are a lot of Bluetooth devices that work just fine, a lot of other protocols that operate in the 2.4 GHz band and work just fine, a lot of other protocols that operate in similarly noisy bands and work just fine and a lot of protocols that are more complex and work just fine.