Range and robustness Bluetooth 3.0 vs. Bluetooth 5.0 @ +4dB

[puz_md]

Does anyone have experience about range, robustness, link stability etc. for Bluetooth 4.0/5.0 (using nRF52832) compared to the old Bluetooth 3.0 standard? For some applications, like high quality audio streaming, Bluetooth 3.0 was and maybe is still better. What about link stability and range in an industrial environment?

We have a product that has a Bluetooth 3.0 module mounted, which was never used, but planned for future use. Now, we are considering to migrate to the new Bluetooth Smart (Bluetooth 5.0) standard, if we can get a link that is at least as stable as Bluetooth 3.0.

[Håkon Alseth]

Hi,

 

Bluetooth 4.0/5.0 (using nRF52832) compared to the old Bluetooth 3.0 standard?

In general, Bluetooth classic and 3.0 is used for high-throughput applications, like uncompressed PCM audio.

When "Low energy" (bluetooth smart) was added in Bluetooth 4.0, its main focus was on lowering the power consumption and creating a new marked for devices that sends a bit of data now-and-then, while still maintaining overall low current consumption.

In Bluetooth 5, the LE part was extended with three RF PHY modes:

* 2Mbit on-air (nRF52810/nRF52832/nRF52840)

* Long range: 500 kBit S2 coded-PHY (nRF52840 only)

* Long range: 125 kBit S8 coded-PHY (nRF52840 only)

This allowed for more throughput with 2 Mbit, while 125k and 500k provides better range coverage. At this moment, we only have one device that can do "long range", and that is the nRF52840.

What about link stability and range in an industrial environment?

This will depend on the area and how it is built up. If you have many smaller rooms, with thick concrete walls in-between each "cubicle", range of any 2.4 GHz protocol will be significantly lowered. In a open area, we have measured >1 kilometer of range with two nRF52840-PDKs. This number is not directly related to how it will work in a noisy industrial area, so I suggest that you get a couple of kits and try it out in your typical application.

Best regards,

Håkon

[puz_md]

Hi Håkon,

thanks for the info. This means that the S2 and S8 coding for better robustness/range will be only available on the nRF52840 which also provides +8 dB transmit power?

It will be a bit difficult to "try it out" as we don't have a typical field application (our product will be used in different scenarios).

Maybe let me ask my question again in a different way:

We want to use Bluetooth communication for industrial purposes. There will be sufficient power (no low power requirements!) and throughput may be low (maybe 64 kbit will be sufficient). Latency should be below 50-100 ms (better 20 ms). Important is link robustness and range. Will there be any benefit in migrating from Bluetooth 3.0 to Bluetooth 4.0/5.0? (And will there be any benefit if we can only use the nRF52832 or nRF82810, but not the nRF52840?)

Best regards,

Michael

[Håkon Alseth]

Hi Michael,

puz_md said:

This means that the S2 and S8 coding for better robustness/range will be only available on the nRF52840 which also provides +8 dB transmit power?

That is correct. Bluetooth Long range ("Coded PHY") will give a better coverage compared to the normal 1 MBit low-energy mode, and this is only available on the nRF52840.

puz_md said:

throughput may be low (maybe 64 kbit will be sufficient). Latency should be below 50-100 ms (better 20 ms)

64 kbit for S8 (125kBit on-air data rate) is most likely not possible, as it would take up all the bandwidth. For 1Mbit or 2Mbit, 64 kBit isn't an issue.

Latency would be equal to your connection interval, and this can be set from 7.5 ms and upwards in .625 ms steps.

puz_md said:

Important is link robustness and range. Will there be any benefit in migrating from Bluetooth 3.0 to Bluetooth 4.0/5.0? (And will there be any benefit if we can only use the nRF52832 or nRF82810, but not the nRF52840?)

Typically, Bluetooth low energy (1Mbit) has a longer range than legacy bluetooth.

The drawback of using Coded PHY is that your packet length will be 2x or 8x longer on-air, and if you have several sensors that you're polling, then I would recommend using standard Low energy 1M on-air datarate and maybe an external RF PA to boost your signal to extend the range.

I'd recommend that you get a couple of our development kits, for instance the nRF52832, and do some simple range testing to see if this is per your requirement.

Best regards,

Håkon

[puz_md]

So, my conclusion is that at least we wouldn't get worse connectivity (for low bandwith) with the nRF52832 compared to Bluetooth 3.0. Is this correct?

I've already done some tests with the nRF51/nRF52 in previous projects, but I had no experience with Bluetooth 3.0 yet, so I just wanted to make sure that we don't lose link stability. In an area "polluted" with WLAN and mobile devices, the link stability and connecting process of the nRF51/nRF52 was rather bad, but it became better late in the evening when people stopped using other wireless technologies. My concern is/was that Bluetooth 3.0 might work better in the "polluted" environment, as it uses a different coding method.

[Håkon Alseth]

Hi,

puz_md said:

So, my conclusion is that at least we wouldn't get worse connectivity (for low bandwith) with the nRF52832 compared to Bluetooth 3.0. Is this correct?

Correct. Normally, Bluetooth Low Energy has a better range than classic bluetooth.

puz_md said:

In an area "polluted" with WLAN and mobile devices, the link stability and connecting process of the nRF51/nRF52 was rather bad, but it became better late in the evening when people stopped using other wireless technologies. My concern is/was that Bluetooth 3.0 might work better in the "polluted" environment, as it uses a different coding method.

Bluetooth (all versions of it) works in the 2.4 GHz ISM band, and will be affected by WLAN and other 2.4 GHz based protocols. This is an issue regardless of which version of bluetooth you're using. BLE is designed to work "around" WLAN by having advertising channels not overlapping with the most common wifi-channels (1,6,11), best shown in this image:

https://www.allaboutcircuits.com/uploads/articles/Bluetooth_and_WLAN_frequencies.jpg

The communication, when in a "dense 2.4 GHz area", would also depend on the channel map chosen. You have up to 37 data channels with BLE, but you do not need to use them all. The link can update the channel map dynamically, for instance if the phone you're using is connected on wifi-channel 1, then your phone can update the channel map to avoid using the lower end of the 2.4 GHz band for bluetooth LE communication.

There are studies available if you want to dig deeper, like the one quoted from this stackoverflow thread:

https://networkengineering.stackexchange.com/questions/39551/why-doesnt-bluetooth-low-energy-interfere-with-wifi

Note: Range-testing is recommended to be done on a design that has optimal output power and a antenna tuned for 2.4 GHz operation. All our development kits are tuned wrt. output power and antenna efficiency, so we recommend to test with these. Antennas will always behave different if copied onto a custom design, as the physical parameters have changed (amount of layers, placement of antenna, size of ground plane, FR4 material properties, component variances in caps/inductors, casings, etc) and will always require tuning.

Best regards,

Håkon