3 ms·

I imagine that power consumption is proportional to amount of data and inversely proportional to latency and data rate. To minimize latency, the transmitting de

I imagine that power consumption is proportional to amount of data and inversely proportional to latency and data rate. To minimize latency, the transmitting device needs to send smaller packets more often, leading to poor efficiency due to overhead. The faster each packet can be sent, though, the less time the transmitter needs to be powered on. I suspect that the only difference in power consumption would be due to the modulations that wifi uses vs. bluetooth, i.e. wifi is able to cram more bits into the same amount of RF energy. The tricky bit with radio comms is that you absolutely have to be able to cope with data loss. The easiest, lowest latency way is to just encode the data in a way that allows it to degrade gracefully. The listener is aware of the data loss, but isn't bothered by it. This implies that there's a lot of redundant information in the data. That is at odds with compression, though, because compression is all about removing redundant information; a loss of any bit of data results in severe degradation. Radio links that send compressed streams of data need to either rely on acknowledgements with retransmission on data loss, or they need to add just enough redundant information for the receiver to reconstruct the original data stream even after expected packet loss. The algorithms that provide that "forward error correction" work by distributing redundant information across multiple packets, which inherently adds latency since the receiver needs multiple packets to decode (or recreate) the payload of single packets.

iancmceachern 6y ago
Not for specific applications like bluetooth headsets. There are application specific ICs that are made for the specific https://www.microchip.com/en-us/products/wireless-connectivity/bluetooth-low-energy/bluetooth-audio-and-voice-solutions# https://www.microchip.com/en-us/products/wireless-connectivi... Much like ASICS are a big step up in performanceand energy efficiency for crypto mining, they are in this application as well.
- sgtnoodle 6y ago
  I'm not sure I follow what you mean. Of course an ASIC can be designed to maximize the efficiency of any given RF device. I personally have a BLE enabled medical device implanted in my chest with a 10+ year battery life. Based on a neat x-ray image I have, it has a single BGA IC, half a dozen ceramic capacitors, what looks like a crystal oscillator, and a couple discrete diodes. My point is that there's inherent energy required to transmit information via radio waves given a specific modulation and framing. Less data takes less energy than more data, and less framing takes less energy than more framing. For the same data rate (digital audio), lower latency requires more power than higher latency because there's more framing overhead. Additionally, because of how noisy the medium is, there's an inherent need for redundancy in the transmitted data, and that redundancy must either be distributed in time or in space. Distributing it in time generally requires less power but inherently adds latency. Distributing it in space means transmitting the signal with more inherent power. That's true whether you use bluetooth or wifi and have an optimized ASIC. The difference between the two is the available modulations and framing. If wifi supports a modulation that's more inherently efficient at transmitting low latency audio data than bluetooth, then it would make sense to implement it. WiFi seemingly isn't designed to do that, though. It's designed to be good at transferring data at orders of magnitude higher data rates, using proportionately higher power. The corresponding framing is designed around that assumption. Legacy bluetooth is terrible, but so is legacy wifi. Presumably, the latest bluetooth standards make use of modern modulations and framing techniques to minimize power consumption and latency appropriate for its use cases. If wifi were strictly better for the same use cases, then the next bluetooth standard would simply be "bluetooth" branding on top of something like wifi-direct.
  - iancmceachern 6y ago
    "If wifi supports a modulation that's more inherently efficient at transmitting low latency audio data than bluetooth, then it would make sense to implement it." I agree, if. In this case the if is a no. Wifi does not allow for transmitting audio more efficiently than Bluetooth. It makes sense, wifi is a much more powerful signal, takes more power to drive and process.

iancmceachern 6y ago

Not for specific applications like bluetooth headsets. There are application specific ICs that are made for the specific https://www.microchip.com/en-us/products/wireless-connectivity/bluetooth-low-energy/bluetooth-audio-and-voice-solutions# https://www.microchip.com/en-us/products/wireless-connectivi... Much like ASICS are a big step up in performanceand energy efficiency for crypto mining, they are in this application as well.

sgtnoodle 6y ago
I'm not sure I follow what you mean. Of course an ASIC can be designed to maximize the efficiency of any given RF device. I personally have a BLE enabled medical device implanted in my chest with a 10+ year battery life. Based on a neat x-ray image I have, it has a single BGA IC, half a dozen ceramic capacitors, what looks like a crystal oscillator, and a couple discrete diodes. My point is that there's inherent energy required to transmit information via radio waves given a specific modulation and framing. Less data takes less energy than more data, and less framing takes less energy than more framing. For the same data rate (digital audio), lower latency requires more power than higher latency because there's more framing overhead. Additionally, because of how noisy the medium is, there's an inherent need for redundancy in the transmitted data, and that redundancy must either be distributed in time or in space. Distributing it in time generally requires less power but inherently adds latency. Distributing it in space means transmitting the signal with more inherent power. That's true whether you use bluetooth or wifi and have an optimized ASIC. The difference between the two is the available modulations and framing. If wifi supports a modulation that's more inherently efficient at transmitting low latency audio data than bluetooth, then it would make sense to implement it. WiFi seemingly isn't designed to do that, though. It's designed to be good at transferring data at orders of magnitude higher data rates, using proportionately higher power. The corresponding framing is designed around that assumption. Legacy bluetooth is terrible, but so is legacy wifi. Presumably, the latest bluetooth standards make use of modern modulations and framing techniques to minimize power consumption and latency appropriate for its use cases. If wifi were strictly better for the same use cases, then the next bluetooth standard would simply be "bluetooth" branding on top of something like wifi-direct.
- iancmceachern 6y ago
  "If wifi supports a modulation that's more inherently efficient at transmitting low latency audio data than bluetooth, then it would make sense to implement it." I agree, if. In this case the if is a no. Wifi does not allow for transmitting audio more efficiently than Bluetooth. It makes sense, wifi is a much more powerful signal, takes more power to drive and process.