Jean Tourrilhes wrote:
>
> Dag wrote :
> > Hi,
> >
> > Since Jean is so active these days, I would like to ask him a question
> > which might be interesing for others as well.
> >
> > Can BT live together with WLAN technologies using FHSS, or will BT
> > interfere with it? I have heard somewhere that BT is much more aggressive
> > than WLAN, and might therefore give bad performance for a WLAN installation
> > when people start carrying BT devices in their pockets.
I work for a major CE company, and in a show environment we had a small
enclosed room (with metal walls) into which we had 802.11 at 11MBps and
streaming BlueTooth working simultaneously right next to each other. No
problems, no missing packets (at least as far as we could see).
However, I absolutely agree that there is a LOT of work to do on how all
the UI stuff is handled. This is going to take a while. On the plus
side, it seems to work and there are a LOT of companies working on it.
Maybe we should focus on improving the UI for IrDA, so that by the time
Bluetooth is perfected we can describe it as "Beaming without
pointing".
After all, by the time Corel, RedHat, Debian, Mandrake, KDE, Gnome et al
have finished a simple UI will allow normal human beings to install and
use something as astoundingly complicated as Linux! :)
> > -- Dag
>
> First let's start with what I think about BT :
> o As a point to point link between two device, it's bloated
> and far too complex (the spec is 1000 pages, plus another 500 pages of
> profiles). 14 packet type at the MAC layer and more than 40 packet
> types at the LLC layer, half a dozen different modes of operation. And
> IrDA was complex ?
> o As a low speed Wireless USB, you may get it to work on good
> days (I mean, after much comliance testing).
> o As a networking technology, it's crap. No native IP support,
> no broadcasting and many limitations. And there is bugs in the spec
> (some procedure are kind of fragile).
> o User interface (how the user interact with the technology)
> is the biggest issue, and BT doesn't seem to have worked much on
> that. For most user, apart some preconfigured configuration (like
> bundle phone dongle + headset), it might just be too complex and
> impossible to understand.
>
> Now, to your question. BT use the same band as 802.11 (and
> other WLAN). And the two won't like each other at close range.
> 802.11 will suffer because it's packet are long and BT is
> jumping around fast, so there is a high probability of getting your
> packets hit. My simulation show a 50% throughput degradation for a FH
> system in the worst conditions (not published yet).
> BT will suffer as well. BT has a low power and poor channel
> rejection, so when tramsitting on the same channel BT will always
> loose the packet but even if 802.11 transmit in an adjacent channel,
> the BT receiver will get swamped by the high power transmissions of
> 802.11. Furthermore, the BT spec is fragile and there is many points
> where the designers have assumed that no packet get lost (when
> switching mode in particular), so this will create delays in
> establising connections and making discoveries.
> Of course, this apply only if the BT network is close to a
> 802.11 node. If the 802.11 node is further away than a few meter,
> there won't be any interference.
>
> But don't worry, BlueTooth is not there yet, and we can
> continue to play safely with our WLAN (now at 11 Mb/s). BT hardware is
> predicted to be available next summer, but they surely won't debug the
> software and provide interoperability for Chrismas 2000. After that,
> 802.11 will be so cheap that BT might be irrelevant...
> Note : you can buy some 802.11 FH for $75/node retail
> (WebGear). Projected BOM of first generation BT is $20/$25 (so when
> you add margins and profits or manufacturer and retailer, it doesn't
> cut the mustard).
>
> On the other hand, a question for you Dag : I'm very curious
> about USB FIR dongle. What do you think of it ? When available ? If
> they can get prices in the $50 region, that might be a hit...
>
> Jean
>
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--
Paul
http://www.geocities.com/~paulbristow
ICQ# 11965223
[EMAIL PROTECTED]
/* With Linux, Java and my Palm, I'm ready to face the day. */
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