Multiple Bluetooth adapters question

>     I know 100 may be too much to ask, but what do you
think would be a
> resonable number if all are transmitting ?

There are 79 channels.  All devices in the same piconet
should always
be on the same channel.  Thus, N independent piconets will
(ignoring
AFH) be uniformly distributed on N channels across the 79
available.
Assuming they are truly independent, the chances that any of
these
piconets choose the same channel is 1 - N! / ( (79^N) *
(79-N)! )  For
1-15, this translates to:

1  0.0
2  0.012658227848101222
3  0.037654222079794852
4  0.074198998456511456
5  0.12107499853466286
6  0.17670316318436774
7  0.23923203686656758
8  0.30664185638471986
9  0.37685533928246973
10  0.44784650316168206
11  0.51773935086273504
12  0.58488956783121493
13  0.64794431702141009
14  0.70587753067611481
15  0.75800049992338558

These numbers reflect the probability that _any_ channel
collision
occurs at a given point in time.  For > 80 active
piconets, there will
_always_ be a channel collision.  It doesn't tell you
expected packet
loss or anything useful like that.  You could calculate an
expected
packet loss based on the expected number of channel
collisions at any
given point in time.  That's a messy formula like
expected(collisions)
= sum_i probability(collisions=i) * i, where
probability(collisions=i) is another messy formula.

Of course, all of this is hand-wavy theory.  It would be
nice if you
could try it out and report some results.

Regards,
Albert

> A related question is : what would be the behavior when
too many devices are
> around ?
>
> Somewhere I read  that BT RF spectrum (2.4 to 2.485
GHz) is devivded in to
> 79 frequency hops.
> Correct me if I am wrong here : What I understand from
this is that only 79
> BT devices can be active in an area ?
> Which approximately gives 10 adapters and 69 client
devices .. does it make
> sense ??
>
> -B
>
>
>
>
> ----- Original Message ----
> From: Albert Huang <albertcsail.mit.edu>
> To: BlueZ users <bluez-userslists.sourceforge.net>
> Sent: Monday, November 13, 2006 11:33:52 AM
> Subject: Re: [Bluez-users] Multiple Bluetooth adapters
question
>
>
> You should experience "graceful" degradation
of performance, as you
> increase the number of colocated transmitting devices. 
100 is pushing
> it, but if not all are transmitting, then it should be
okay.
>
> -albert
>
> On 11/13/06, Brown Dwarf <brown_drfyahoo.com> wrote:
> >
> > Hi all,
> >      This may be a FAQ, but I could not locate an
definit answer.
> >
> > I want to what are all the implications of having
multiple bluetooth
> > adapters on a machine.
> > As you might have guessed, I would like to host
more than 7 (say 100 ) BT
> > connections (SPP) at a time. I noticed BlueZ
supports upto 16 adapters -
> > which means it can support upto 112 connections at
a time ??
> >
> > Anybody ever tried it ?
> >
> > In other words, if I have 16 adapters installed on
a box and have 100
> client
> > BT devices around, can they all communicate to one
of those 16 adapters at
> > any time ? I don't know much about the RF side of
the problem, but I am
> > little concerned about the fact that BT band-width
is small. So can all
> > those devices resonabily share the narrow
frequency space ?
> >
> > Any comments or pointers to any tech infomation /
articles / resources
> will
> > be greatly appreciated.
> >
> > thanks in advance.
> > -B
> >
> >
>
------------------------------------------------------------
-------------
> > Using Tomcat but need to do more? Need to support
web services, security?
> > Get stuff done quickly with pre-integrated
technology to make your job
> > easier
> > Download IBM WebSphere Application Server v.1.0.1
based on Apache Geronimo
> >
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> >
> > _______________________________________________
> > Bluez-users mailing list
> > Bluez-userslists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/bluez-users

> >
> >
> >
>
>
------------------------------------------------------------
-------------
> Using Tomcat but need to do more? Need to support web
services, security?
> Get stuff done quickly with pre-integrated technology
to make your job
> easier
> Download IBM WebSphere Application Server v.1.0.1 based
on Apache Geronimo
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> _______________________________________________
> Bluez-users mailing list
> Bluez-userslists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users

>
>
>
>
------------------------------------------------------------
-------------
> Using Tomcat but need to do more? Need to support web
services, security?
> Get stuff done quickly with pre-integrated technology
to make your job
> easier
> Download IBM WebSphere Application Server v.1.0.1 based
on Apache Geronimo
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
>
> _______________________________________________
> Bluez-users mailing list
> Bluez-userslists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users

>
>
>

------------------------------------------------------------
-------------
Using Tomcat but need to do more? Need to support web
services, security?
Get stuff done quickly with pre-integrated technology to
make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on
Apache Geronimo
http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Bluez-users mailing list
Bluez-userslists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users

>     I know 100 may be too much to ask, but what do you
think would be a
> resonable number if all are transmitting ?

There are 79 channels.  All devices in the same piconet
should always
be on the same channel.  Thus, N independent piconets will
(ignoring
AFH) be uniformly distributed on N channels across the 79
available.
Assuming they are truly independent, the chances that any of
these
piconets choose the same channel is 1 - N! / ( (79^N) *
(79-N)! )  For
1-15, this translates to:

1  0.0
2  0.012658227848101222
3  0.037654222079794852
4  0.074198998456511456
5  0.12107499853466286
6  0.17670316318436774
7  0.23923203686656758
8  0.30664185638471986
9  0.37685533928246973
10  0.44784650316168206
11  0.51773935086273504
12  0.58488956783121493
13  0.64794431702141009
14  0.70587753067611481
15  0.75800049992338558

These numbers reflect the probability that _any_ channel
collision
occurs at a given point in time.  For > 80 active
piconets, there will
_always_ be a channel collision.  It doesn't tell you
expected packet
loss or anything useful like that.  You could calculate an
expected
packet loss based on the expected number of channel
collisions at any
given point in time.  That's a messy formula like
expected(collisions)
= sum_i probability(collisions=i) * i, where
probability(collisions=i) is another messy formula.

Of course, all of this is hand-wavy theory.  It would be
nice if you
could try it out and report some results.

Regards,
Albert

> A related question is : what would be the behavior when
too many devices are
> around ?
>
> Somewhere I read  that BT RF spectrum (2.4 to 2.485
GHz) is devivded in to
> 79 frequency hops.
> Correct me if I am wrong here : What I understand from
this is that only 79
> BT devices can be active in an area ?
> Which approximately gives 10 adapters and 69 client
devices .. does it make
> sense ??
>
> -B
>
>
>
>
> ----- Original Message ----
> From: Albert Huang <albertcsail.mit.edu>
> To: BlueZ users <bluez-userslists.sourceforge.net>
> Sent: Monday, November 13, 2006 11:33:52 AM
> Subject: Re: [Bluez-users] Multiple Bluetooth adapters
question
>
>
> You should experience "graceful" degradation
of performance, as you
> increase the number of colocated transmitting devices. 
100 is pushing
> it, but if not all are transmitting, then it should be
okay.
>
> -albert
>
> On 11/13/06, Brown Dwarf <brown_drfyahoo.com> wrote:
> >
> > Hi all,
> >      This may be a FAQ, but I could not locate an
definit answer.
> >
> > I want to what are all the implications of having
multiple bluetooth
> > adapters on a machine.
> > As you might have guessed, I would like to host
more than 7 (say 100 ) BT
> > connections (SPP) at a time. I noticed BlueZ
supports upto 16 adapters -
> > which means it can support upto 112 connections at
a time ??
> >
> > Anybody ever tried it ?
> >
> > In other words, if I have 16 adapters installed on
a box and have 100
> client
> > BT devices around, can they all communicate to one
of those 16 adapters at
> > any time ? I don't know much about the RF side of
the problem, but I am
> > little concerned about the fact that BT band-width
is small. So can all
> > those devices resonabily share the narrow
frequency space ?
> >
> > Any comments or pointers to any tech infomation /
articles / resources
> will
> > be greatly appreciated.
> >
> > thanks in advance.
> > -B
> >
> >
>
------------------------------------------------------------
-------------
> > Using Tomcat but need to do more? Need to support
web services, security?
> > Get stuff done quickly with pre-integrated
technology to make your job
> > easier
> > Download IBM WebSphere Application Server v.1.0.1
based on Apache Geronimo
> >
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> >
> > _______________________________________________
> > Bluez-users mailing list
> > Bluez-userslists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/bluez-users

> >
> >
> >
>
>
------------------------------------------------------------
-------------
> Using Tomcat but need to do more? Need to support web
services, security?
> Get stuff done quickly with pre-integrated technology
to make your job
> easier
> Download IBM WebSphere Application Server v.1.0.1 based
on Apache Geronimo
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> _______________________________________________
> Bluez-users mailing list
> Bluez-userslists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users

>
>
>
>
------------------------------------------------------------
-------------
> Using Tomcat but need to do more? Need to support web
services, security?
> Get stuff done quickly with pre-integrated technology
to make your job
> easier
> Download IBM WebSphere Application Server v.1.0.1 based
on Apache Geronimo
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
>
> _______________________________________________
> Bluez-users mailing list
> Bluez-userslists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users

>
>
>

------------------------------------------------------------
-------------
Using Tomcat but need to do more? Need to support web
services, security?
Get stuff done quickly with pre-integrated technology to
make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on
Apache Geronimo
http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Bluez-users mailing list
Bluez-userslists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users

>     I know 100 may be too much to ask, but what do you
think would be a
> resonable number if all are transmitting ?

There are 79 channels.  All devices in the same piconet
should always
be on the same channel.  Thus, N independent piconets will
(ignoring
AFH) be uniformly distributed on N channels across the 79
available.
Assuming they are truly independent, the chances that any of
these
piconets choose the same channel is 1 - N! / ( (79^N) *
(79-N)! )  For
1-15, this translates to:

1  0.0
2  0.012658227848101222
3  0.037654222079794852
4  0.074198998456511456
5  0.12107499853466286
6  0.17670316318436774
7  0.23923203686656758
8  0.30664185638471986
9  0.37685533928246973
10  0.44784650316168206
11  0.51773935086273504
12  0.58488956783121493
13  0.64794431702141009
14  0.70587753067611481
15  0.75800049992338558

These numbers reflect the probability that _any_ channel
collision
occurs at a given point in time.  For > 80 active
piconets, there will
_always_ be a channel collision.  It doesn't tell you
expected packet
loss or anything useful like that.  You could calculate an
expected
packet loss based on the expected number of channel
collisions at any
given point in time.  That's a messy formula like
expected(collisions)
= sum_i probability(collisions=i) * i, where
probability(collisions=i) is another messy formula.

Of course, all of this is hand-wavy theory.  It would be
nice if you
could try it out and report some results.

Regards,
Albert

> A related question is : what would be the behavior when
too many devices are
> around ?
>
> Somewhere I read  that BT RF spectrum (2.4 to 2.485
GHz) is devivded in to
> 79 frequency hops.
> Correct me if I am wrong here : What I understand from
this is that only 79
> BT devices can be active in an area ?
> Which approximately gives 10 adapters and 69 client
devices .. does it make
> sense ??
>
> -B
>
>
>
>
> ----- Original Message ----
> From: Albert Huang <albertcsail.mit.edu>
> To: BlueZ users <bluez-userslists.sourceforge.net>
> Sent: Monday, November 13, 2006 11:33:52 AM
> Subject: Re: [Bluez-users] Multiple Bluetooth adapters
question
>
>
> You should experience "graceful" degradation
of performance, as you
> increase the number of colocated transmitting devices. 
100 is pushing
> it, but if not all are transmitting, then it should be
okay.
>
> -albert
>
> On 11/13/06, Brown Dwarf <brown_drfyahoo.com> wrote:
> >
> > Hi all,
> >      This may be a FAQ, but I could not locate an
definit answer.
> >
> > I want to what are all the implications of having
multiple bluetooth
> > adapters on a machine.
> > As you might have guessed, I would like to host
more than 7 (say 100 ) BT
> > connections (SPP) at a time. I noticed BlueZ
supports upto 16 adapters -
> > which means it can support upto 112 connections at
a time ??
> >
> > Anybody ever tried it ?
> >
> > In other words, if I have 16 adapters installed on
a box and have 100
> client
> > BT devices around, can they all communicate to one
of those 16 adapters at
> > any time ? I don't know much about the RF side of
the problem, but I am
> > little concerned about the fact that BT band-width
is small. So can all
> > those devices resonabily share the narrow
frequency space ?
> >
> > Any comments or pointers to any tech infomation /
articles / resources
> will
> > be greatly appreciated.
> >
> > thanks in advance.
> > -B
> >
> >
>
------------------------------------------------------------
-------------
> > Using Tomcat but need to do more? Need to support
web services, security?
> > Get stuff done quickly with pre-integrated
technology to make your job
> > easier
> > Download IBM WebSphere Application Server v.1.0.1
based on Apache Geronimo
> >
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> >
> > _______________________________________________
> > Bluez-users mailing list
> > Bluez-userslists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/bluez-users

> >
> >
> >
>
>
------------------------------------------------------------
-------------
> Using Tomcat but need to do more? Need to support web
services, security?
> Get stuff done quickly with pre-integrated technology
to make your job
> easier
> Download IBM WebSphere Application Server v.1.0.1 based
on Apache Geronimo
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> _______________________________________________
> Bluez-users mailing list
> Bluez-userslists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users

>
>
>
>
------------------------------------------------------------
-------------
> Using Tomcat but need to do more? Need to support web
services, security?
> Get stuff done quickly with pre-integrated technology
to make your job
> easier
> Download IBM WebSphere Application Server v.1.0.1 based
on Apache Geronimo
> http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
>
> _______________________________________________
> Bluez-users mailing list
> Bluez-userslists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users

>
>
>

------------------------------------------------------------
-------------
Using Tomcat but need to do more? Need to support web
services, security?
Get stuff done quickly with pre-integrated technology to
make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on
Apache Geronimo
http://sel.as-us.falkag.net/
sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Bluez-users mailing list
Bluez-userslists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users