Audio "Broadcast" & receive solution?

RE: Audio "Broadcast" & receive solution?

Ole Bauck — Wed, 08 Feb 2017 12:07:41 GMT

Bluetooth 5 has some features that are specifically made for doing large data transfer over advertising, like for example audio, see here. As the site says, both nRF52832 and nRF52840 have features that are compatible with bluetooth 5, except for that the nRF52832 don't have the long range option (125kbps). The SoftDevices does not support advertising extensions yet, but it will come in the future.

That said, having 200 meter range and sending audio will be hard as both Jan and Wojtek says. If you want that range you should go for 125kbps on-air datarate. Based on the receiver sensitivity this has about twice the range compared to 1Mbps mode and about four times the range compared to 2Mpbs mode (6dBm is about double the range). But if you go for long range you get low throughput and for audio you need high throughput. You can't have both at the same time.

ESB (without ack) is a better option when it comes to throughput for connection less links, but here the receiver sensitivity is lower than for BLE operations.

RE: Audio "Broadcast" & receive solution?

endnode — Wed, 08 Feb 2017 11:36:50 GMT

Well if you code redundancy as one-way (which is definitely not as efficient as two-way connection based thing) then it could work.

RE: Audio "Broadcast" & receive solution?

Wojtek — Wed, 08 Feb 2017 10:14:01 GMT

If it could work in one to one, it will work the same in one to many, when using shockburst (no acking etc). I think nRF5x are really great chips and I like to work with them, but i don't think it suits your application though. I would look for other solution.

RE: Audio "Broadcast" & receive solution?

endnode — Wed, 08 Feb 2017 10:08:49 GMT

I would suggest to go with what Wojtek wrote: proprietary protocol such as Nordics' (enhanced)Shockburst. The problem with multimedia such as audio is quality of service aka packet loss and recovery on top of link layer. Because if your sound is fine with lower sampling rate than maximum throughput (and let's assume this would be the case with nRF52) you don't want to hear crackling and silent gaps but rather use some clever mechanism with redundancy so up to some packet error/loss rate it wouldn't effect your audio application. Anyway I still believe that low power radio chips such as nRF5x are maybe usable for some "crazy" point to point audio transfer (low quality) with pretty high effort in developing whole protocol and then actual implementation in the FW but definitely not in "one to many" broadcasting scenarios such as yours.

RE: Audio "Broadcast" & receive solution?

Wojtek — Wed, 08 Feb 2017 10:01:36 GMT

I don't know where did you read about 5mbps for nrf52840, so just to clarify - it has 2M datarate in high speed, so it is not possible to have 5M throughput. Consider using pure shockburst, without Bluetooth overhead. I managed to get about 1,9Mbps on shockburst, using nRF52. But still, getting 200m range on that data rate is not possible in my opinion. 60m maybe, if you do your antennas properly.

RE: Audio "Broadcast" & receive solution?

Mitch996 — Wed, 08 Feb 2017 09:56:37 GMT

Hello Jan, forget about BLE then. Will bluetooth 5 be up to the task, with advertising, or anything similar?

Also, I'm curious, what's limiting the transfer rate to mere kbps?

RE: Audio "Broadcast" & receive solution?

endnode — Wed, 08 Feb 2017 08:23:23 GMT

Hi Mitch,

I believe you cannot achieve anything above few kbps with standard BLE broadcasting (ADV_IND packets) so to leverage these Mbps data rates you would be building totally custom stack and protocol. It might still work but you probably won't use anything from BLE stack and spec so forget about things like Advertising, GAP etc. Just speak about raw packets, frequencies and protocols. I believe you would flood particular channels pretty heavily so it would work only if there is no 2.4GHz traffic in the area. Overall it doesn't look like easy to build and there will be probably dozens of different technologies (like FM radio?;))) with off-the-shelf hardware usable for this kind of application.

Cheers Jan