Analysis of energy consumption of Bluetooth Low Energy versus Bluetooth Classic

The &quot;LE&quot; is more about <i>behavior</i>, rather than some power-saving tech. It affords low-energy-use behavior. Short bursts, <i>ad hoc</i> connections, small amounts of data, etc. If we make it behave like Classic, it will suck energy like Classic.<p>I like using BLE, more than Classic (BR&#x2F;EDR). It&#x27;s a bit pedantic, getting things set up, but that can be abstracted, fairly easily[0].<p>If we program for iOS&#x2F;WatchOS&#x2F;TVOS&#x2F;iPadOS, we&#x27;ll generally be using LE, as Core Bluetooth is designed around LE. Classic is there, but IOBluetooth is only meant for MacOS, and is a private API, on the other platforms.<p>LE is basically meant for short busts of control information, or small bits of data. Its encryption is pretty good. You can actually have a meaningful dialogue, just using the advertising information, so a connection is not always required (beacons use this).<p>I have heard that they will be adding some high data-rate stuff to LE, so we may be seeing true LE headphones, in the future.<p>[0] <a href="https:&#x2F;&#x2F;github.com&#x2F;RiftValleySoftware&#x2F;RVS_BlueThoth" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;RiftValleySoftware&#x2F;RVS_BlueThoth</a>

BLE was designed as a super low bitrate intermittent protocol, and named with that application in mind. It was designed to spend 99% of its time &quot;asleep&quot;.<p>Not too surprising it&#x27;s similar power to Classic when doing similar things.<p>But also, a good study to actually measure it!

The institution credited, Jönköping University, is notable in Sweden for &#x2F;not&#x2F; being a university and skirting the name issue by being named “Jönköping University” in Swedish as well. Make of that what you will but to me it seems like a con.<p>diva-portal.org is not a journal, it is simply a repository of all academic texts from Swedish institutions.

They mention the Power Profiler Kit 2 (PPK2) to measure power usage. I&#x27;ve been using it for a few months with microcontrollers and have found it very useful. The amount of precision it&#x27;s capable of with high-frequency measurements is extraordinary, I was able to spot when the MCU was running various functions just from the power draw. It goes down to 200nA and can produce 100,000 samples&#x2F;sec.<p>Alternatives like USB power meters[2] are still useful and can be cheap, but you don&#x27;t get raw data from them and just have to read the value from the display. For comparison DigiKey has the PPK2 listed for $92.50.<p>[1] <a href="https:&#x2F;&#x2F;www.nordicsemi.com&#x2F;Products&#x2F;Development-hardware&#x2F;Power-Profiler-Kit-2" rel="nofollow">https:&#x2F;&#x2F;www.nordicsemi.com&#x2F;Products&#x2F;Development-hardware&#x2F;Pow...</a><p>[2] <a href="https:&#x2F;&#x2F;amazon.com&#x2F;s?k=usb+power+meter" rel="nofollow">https:&#x2F;&#x2F;amazon.com&#x2F;s?k=usb+power+meter</a>

The small packet size is what is constraining BLE in the energy consumption comparison. It really wasn&#x27;t meant for continuously streaming music.<p>When advertising every few seconds, like an Apple AirTag does, the energy usage averages about 5uA. That certainly beats the heck out of Bluetooth Classic.<p>They just have different use cases. Eventually BLE will add a long packet size feature and win out. Between music and firmware uploading, there are lots of use cases nowadays. Nobody wants Bluetooth Classic, it&#x27;s 20+ years old and uses a whole different stack.

They found usecases when classic is better.<p>BLE is very good for operating a sensor or a beacon for years on a coin cell. That’s why it’s so popular.<p>Also because of the easier api&#x2F;interface to exchange data compared to the classic bluetooth.

Note that this is a bachelor thesis based on testing of a single product (Jody-W263). Probably shouldn&#x27;t be quoted now as &#x27;universal truth&#x27;.

Fair use:<p><i>7.1 Conclusions The purpose of this study was to research and investigate the potential existence of a breaking point where BLE becomes less efficient than BR&#x2F;EDR in terms of energy consumption. The results from the conducted experiments show that BLE has overall worse energy consumption efficiency than BR&#x2F;EDR and that there is no breaking point since BLE is shown to be worse.</i>

On this topic: I&#x27;m very interested in streaming accelerometer data in real time from a wrist worn device to a body mounted LED controller. My goal is to modify the LEDs animations based on the hand position. Given the sensor bitrate and low latency required for this data, it would appears that BT Classic may be better solution than BLE. Beyond the power consumption needs, BLE connectionless broadcasting of the data seems easier to handle with than having to manage pairing two device. You could simply pick the strongest signal and be reasonable assured that it&#x27;s your personally worn wrist device.<p>Am I missing something?

When I was a PhD student, we did similar measurements for LTE and WiFi for multipath TCP. These are non-trivial measurements due to lots of overlaying effects and I honestly speaking do not trust a BSc student to get this right.<p>Besides that I think the measurement scenario is unfair, as BTLE was designed for a different use case, i.e., always on and always able to overhear beacons. Comparing BT and BTLE for data transmission only is like measuring a race between a horse and a fish in the open sea.

This is about the newer LE 2M PHY, which was added for &quot;replacing Classic&quot; (which is 2-3M) use cases. It&#x27;s not surprising that it&#x27;s not as efficient as the more widely used 1M PHY.

Its important to note that this study has only tested one Bluetooth stack.

&gt; The experiments showed that when using BR&#x2F;EDR’s 2 Mb&#x2F;s, the practical throughput were on average 0.786 Mb&#x2F;s. [...] Meanwhile, when using BLE’s 1M PHY, the average throughput were around 0.522 Mb&#x2F;s and 0.938 Mb&#x2F;s when using 2M PHY. The bit rate speed for the BR&#x2F;EDR 1Mb&#x2F;s mode were at an average of 0.104 Mb&#x2F;s. Using these results, it shows that on average, the BR&#x2F;EDR throughput speeds are faster than the BLE throughput speeds.<p>I&#x27;m probably misunderstanding what the author intended here, but this just seems wrong. 0.104Mb&#x2F;s (BR&#x2F;EDR 1 Mb&#x2F;s mode) is not faster than 0.522Mb&#x2F;s (BLE 1M mode), nor is 0.786Mb&#x2F;s (BR&#x2F;EDR 2 Mb&#x2F;s mode) faster than 0.938Mb&#x2F;s (BLE 2M mode). I can&#x27;t see how you would reach the conclusion that BR&#x2F;EDR is faster &quot;on average&quot; than BLE with those results unless you&#x27;re also factoring in BR&#x2F;EDR&#x27;s 3 Mb&#x2F;s mode in some way, even though there is no BLE equivalent to compare it to.

What&#x27;s going to matter for audio streaming in an automotive (the case they are concerned about) is the energy consumption in the receiver, not the transmitter. They are measuring the second.

Thanks for sharing!

That’s… odd? I would’ve assumed that LE was designed with both theory and practical testing - how could classic be better at everything?

tldr?