Re: [bluetooth] question...

[Alban Villain <Alban.Villain@inventel.fr>]

>On Friday 17 January 2003 15:01, Alban Villain wrote:
> > At last a Bluetooth stack crash may occur because of this bad packet....
> > and then you need to restart your device !!! However, as it may happen
> > statistically 1 time every lots of hours it is not so dramatic... because
> > in general Windows (if you use a PC as Bluetooth host) will have crashed
> > before that ;-) I
>
>Well, that is assuming Windows. How about non-personal equipment, operating
>without human intervention? My upcoming release of products, are expected to
>run years without human interaction, and are not allowed to "crash".
>I am not sure if you are saying that there is built-in problems that BT 
>stacks
>will crash by design, which is worrying, or that they are just buggy, because
>of bad implementations.

It is not specific to BT stacks. It concerns data transmission systems in 
general, and wireless systems in particular. It has nothing to see with 
implementation.

Do you agree or not that corrupted baseband packets can pass all the 
baseband tests ?
  - FEC2/3 is not able to correct or detect all errors ;
  - CRC may not detect all errors ;
  - So there is a very little but non zero probability that corrupted 
packets passes through baseband checkings...

For your products, did you experience unexplained crashes ?
The time between 2 crashes due to a non detected corrupted packet may be 
very large. I didn't estimate it, but it is possible to do it using 
probabilistic properties of error correction and detection codes used in 
Bluetooth. It may be many months, or years.

Alban

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