Hacker News Reader

Comment by Gibbon1 | Hacker News Reader

1. The quality of service for RF vs a wire sucks big phat donkey balls.

2. For low power devices like Bluetooth, even worse than that.

3. Bluetooth is a frequency hopper. Frequency hoppers have all sorts of synchronization problems. That plays havoc with link maintenance algorithms.

3b. Distributed link maintenance with no central control is a hard problem.

4. The people that designed the original spec didn't know what they were doing.

5. The baseband spec is very complicated. And thus hard to get right on all cases. And there are multiple layers each with a different party responsible for implementation.

6. Bluetooth devices are designed by groups working for a large number of manufacturers none of whom have license to help each other.

Items 1-3 explains why Ethernet tends to just work and Wifi/Bluetooth kinda sucks.

Item 4 explains why Wifi works better than Bluetooth.

Items 5-6 explains why your cell phone generally just works even though it uses RF.

View on HN

#4 makes me laugh because I had that thought when I was trying to work with bluetooth. I think the real problem is two-fold. The original spec required approval from all members of the consortium. I think a lot of things were left out that are really important, such as security. I know they had security from the start, but really, it's bullshit. Plus the original chipsets were incredibly expensive, and my pure speculative thought is that they cut corners (the firmware part) to bring them out to market. I was really surprised, shouldn't have been with hindsight, to see when bluetooth chipsets started to reach price parity with wifi chipsets.

The second thing is that much of the low level firmware for the stack is closed source stuff that is written in house. I suspect, after working with some of that shit, that it's poorly done and is a major cause of unreliability. Don't know if it would make any difference if it was open sourced, because the hardware/software combo is a lot like what you see with graphics cards. Everyone has their own secret sauce and they don't want to show it to the world.

I remember watching a tech news report on cable TV (yeah, that long ago) about a hot new tech called 'Bluetooth' that was going to revolutionize device interoperability, and the BT chipset would be at most $5 of the device cost.... until that never happened.

It actually did, charmingly. usually I just click upvote on these but it was stunning to read one and think "wait...that is exactly what happened, even if its not perfect"

Yeah, but how long did it take to truly drop to the $5 mark? When bluetooth stuff came out (mice, keyboards, etc.) they were exorbitantly expensive. It was way cheaper for manufacturers to sell stuff with their own RF dongles instead of using BT.

I recall buying a USB Bluetooth adapter in the mid 2000's that was maybe $12 shipped from Asia. If that was a the cost to the consumer for a device that was mostly a bluetooth radio I suspect that the cost to add bluetooth to a high volume product was probably at or below $5 ~15 years ago.

I remember the marketing guys had this spiel that WiFi was for businesses and that consumers would use Bluetooth for wireless networking. Because at $50-100 obviously WiFi was 'too expensive' for home use. LOL.

I think WIFI chipsets hit $5 before Bluetooth ones.

Reminds me of a problem with how people think of 'low power RF'. You don't actually care so much about continuous current draw (within reason) what you care about is energy per bit. Which means high bandwidth doesn't penalize you as much as you would assume. Bonus in practice the longer your packet takes to transmit the higher the chance it gets clobbered. Bluetooth going with a low bandwidth low continuous power radio; FAIL.

I was writing firmware for RX transceivers when Bluetooth was specified. I feel like they wrote the spec with very little input from chip designers and without building prototype hardware.

That's why they chose a GFSK frequency hopper. Which ignored the expected advances in low power spread spectrum radio's. Previously the power requirements for a spread spectrum receiver were way too high, but within a two years of releasing the spec power requirements dropped dramatically. RF chip designers new this was going to happen.

Same time their baseband requirements were almost impossible to meet with a low power budget even in 2003 or so. So you had a crummy GFSK radio, frequency hopper. Married to a fat piggy baseband spec.

What I remember is about two dozen design groups spent a couple of years developing Bluetooth hardware and by 2004 or so exactly three of them succeeded. That's big indictment of the spec. And here 20 years later it still sucks.

Reply on news.ycombinator.com