From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <20061114180917.64164.qmail@web32913.mail.mud.yahoo.com> Date: Tue, 14 Nov 2006 10:09:17 -0800 (PST) From: Brown Dwarf To: BlueZ users MIME-Version: 1.0 Subject: Re: [Bluez-users] Multiple Bluetooth adapters question Reply-To: BlueZ users List-Id: BlueZ users List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============1287262197==" Sender: bluez-users-bounces@lists.sourceforge.net Errors-To: bluez-users-bounces@lists.sourceforge.net --===============1287262197== Content-Type: multipart/alternative; boundary="0-109966985-1163527757=:62991" --0-109966985-1163527757=:62991 Content-Type: text/plain; charset=ascii Content-Transfer-Encoding: quoted-printable Albert,=0A Thank you for the explanation. This is something I was lookin= g for. =0AUnfortunately I don't have the abundance of BT devices at this po= int to run a test.=0AI'll definitly let you all know if I get to test it - = ever :)=0A =0Athanks again=0A~B=0A=0A=0A----- Original Message ----=0AFrom:= Albert Huang =0ATo: BlueZ users =0ASent: Monday, November 13, 2006 10:54:15 PM=0ASubject: Re= : [Bluez-users] Multiple Bluetooth adapters question=0A=0A=0A> I know 1= 00 may be too much to ask, but what do you think would be a=0A> resonable n= umber if all are transmitting ?=0A=0AThere are 79 channels. All devices in= the same piconet should always=0Abe on the same channel. Thus, N independ= ent piconets will (ignoring=0AAFH) be uniformly distributed on N channels a= cross the 79 available.=0AAssuming they are truly independent, the chances = that any of these=0Apiconets choose the same channel is 1 - N! / ( (79^N) *= (79-N)! ) For=0A1-15, this translates to:=0A=0A1 0.0=0A2 0.012658227848= 101222=0A3 0.037654222079794852=0A4 0.074198998456511456=0A5 0.121074998= 53466286=0A6 0.17670316318436774=0A7 0.23923203686656758=0A8 0.306641856= 38471986=0A9 0.37685533928246973=0A10 0.44784650316168206=0A11 0.5177393= 5086273504=0A12 0.58488956783121493=0A13 0.64794431702141009=0A14 0.7058= 7753067611481=0A15 0.75800049992338558=0A=0AThese numbers reflect the prob= ability that _any_ channel collision=0Aoccurs at a given point in time. Fo= r > 80 active piconets, there will=0A_always_ be a channel collision. It d= oesn't tell you expected packet=0Aloss or anything useful like that. You c= ould calculate an expected=0Apacket loss based on the expected number of ch= annel collisions at any=0Agiven point in time. That's a messy formula like= expected(collisions)=0A=3D \sum_i probability(collisions=3Di) * i, where= =0Aprobability(collisions=3Di) is another messy formula.=0A=0AOf course, al= l of this is hand-wavy theory. It would be nice if you=0Acould try it out = and report some results.=0A=0ARegards,=0AAlbert=0A=0A> A related question i= s : what would be the behavior when too many devices are=0A> around ?=0A>= =0A> Somewhere I read that BT RF spectrum (2.4 to 2.485 GHz) is devivded i= n to=0A> 79 frequency hops.=0A> Correct me if I am wrong here : What I unde= rstand from this is that only 79=0A> BT devices can be active in an area ?= =0A> Which approximately gives 10 adapters and 69 client devices .. does it= make=0A> sense ??=0A>=0A> -B=0A>=0A>=0A>=0A>=0A> ----- Original Message --= --=0A> From: Albert Huang =0A> To: BlueZ users =0A> Sent: Monday, November 13, 2006 11:33:52 = AM=0A> Subject: Re: [Bluez-users] Multiple Bluetooth adapters question=0A>= =0A>=0A> You should experience "graceful" degradation of performance, as yo= u=0A> increase the number of colocated transmitting devices. 100 is pushin= g=0A> it, but if not all are transmitting, then it should be okay.=0A>=0A> = -albert=0A>=0A> On 11/13/06, Brown Dwarf wrote:=0A> >= =0A> > Hi all,=0A> > This may be a FAQ, but I could not locate an defi= nit answer.=0A> >=0A> > I want to what are all the implications of having m= ultiple bluetooth=0A> > adapters on a machine.=0A> > As you might have gues= sed, I would like to host more than 7 (say 100 ) BT=0A> > connections (SPP)= at a time. I noticed BlueZ supports upto 16 adapters -=0A> > which means i= t can support upto 112 connections at a time ??=0A> >=0A> > Anybody ever tr= ied it ?=0A> >=0A> > In other words, if I have 16 adapters installed on a b= ox and have 100=0A> client=0A> > BT devices around, can they all communicat= e to one of those 16 adapters at=0A> > any time ? I don't know much about t= he RF side of the problem, but I am=0A> > little concerned about the fact t= hat BT band-width is small. So can all=0A> > those devices resonabily share= the narrow frequency space ?=0A> >=0A> > Any comments or pointers to any t= ech infomation / articles / resources=0A> will=0A> > be greatly appreciated= .=0A> >=0A> > thanks in advance.=0A> > -B=0A> >=0A> >=0A> -----------------= --------------------------------------------------------=0A> > Using Tomcat= but need to do more? Need to support web services, security?=0A> > Get stu= ff done quickly with pre-integrated technology to make your job=0A> > easie= r=0A> > Download IBM WebSphere Application Server v.1.0.1 based on Apache G= eronimo=0A> >=0A> http://sel.as-us.falkag.net/sel?cmd=3Dlnk&kid=3D120709&bi= d=3D263057&dat=3D121642=0A> >=0A> > _______________________________________= ________=0A> > Bluez-users mailing list=0A> > Bluez-users@lists.sourceforge= .net=0A> > https://lists.sourceforge.net/lists/listinfo/bluez-users=0A> >= =0A> >=0A> >=0A>=0A> ------------------------------------------------------= -------------------=0A> Using Tomcat but need to do more? Need to support w= eb services, security?=0A> Get stuff done quickly with pre-integrated techn= ology to make your job=0A> easier=0A> Download IBM WebSphere Application Se= rver v.1.0.1 based on Apache Geronimo=0A> http://sel.as-us.falkag.net/sel?c= md=3Dlnk&kid=3D120709&bid=3D263057&dat=3D121642=0A> _______________________= ________________________=0A> Bluez-users mailing list=0A> Bluez-users@lists= .sourceforge.net=0A> https://lists.sourceforge.net/lists/listinfo/bluez-use= rs=0A>=0A>=0A>=0A> --------------------------------------------------------= -----------------=0A> Using Tomcat but need to do more? Need to support web= services, security?=0A> Get stuff done quickly with pre-integrated technol= ogy to make your job=0A> easier=0A> Download IBM WebSphere Application Serv= er v.1.0.1 based on Apache Geronimo=0A> http://sel.as-us.falkag.net/sel?cmd= =3Dlnk&kid=3D120709&bid=3D263057&dat=3D121642=0A>=0A> _____________________= __________________________=0A> Bluez-users mailing list=0A> Bluez-users@lis= ts.sourceforge.net=0A> https://lists.sourceforge.net/lists/listinfo/bluez-u= sers=0A>=0A>=0A>=0A=0A-----------------------------------------------------= --------------------=0AUsing Tomcat but need to do more? Need to support we= b services, security?=0AGet stuff done quickly with pre-integrated technolo= gy to make your job easier=0ADownload IBM WebSphere Application Server v.1.= 0.1 based on Apache Geronimo=0Ahttp://sel.as-us.falkag.net/sel?cmd=3Dlnk&ki= d=3D120709&bid=3D263057&dat=3D121642=0A____________________________________= ___________=0ABluez-users mailing list=0ABluez-users@lists.sourceforge.net= =0Ahttps://lists.sourceforge.net/lists/listinfo/bluez-users=0A=0A --0-109966985-1163527757=:62991 Content-Type: text/html; charset=ascii Content-Transfer-Encoding: quoted-printable
 
=0A
Albert,
=0A
Unfortunately I don't have the abundance o= f BT devices at this point to run a test.
=0A
I'll definitly = let you all know if I get to test it - ever :)
=0A
 =0A
thanks again
=0A
~B

=0A
= ----- Original Message ----
From: Albert Huang <albert@csail.mit.edu&= gt;
To: BlueZ users <bluez-users@lists.sourceforge.net>
Sent: M= onday, November 13, 2006 10:54:15 PM
Subject: Re: [Bluez-users] Multiple= Bluetooth adapters question

=0A
>     I = know 100 may be too much to ask, but what do you think would be a
> r= esonable number if all are transmitting ?

There are 79 channels.&nbs= p; All devices in the same piconet should always
be on the same cha= nnel.  Thus, N independent piconets will (ignoring
AFH) be uni= formly 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 &nb= sp;0.23923203686656758
8  0.30664185638471986
9  = 0.37685533928246973
10  0.44784650316168206
11  0= .51773935086273504
12  0.58488956783121493
13  0.= 64794431702141009
14  0.70587753067611481
15  0.7= 5800049992338558

These numbers reflect the probability that _any_ ch= annel 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.&n= bsp; You could calculate an expected
packet loss based on the expec= ted number of channel collisions at any
given point in time.  = That's a messy formula like expected(collisions)
=3D \sum_i probability(collisio= ns=3Di) * i, where
probability(collisions=3Di) 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&nbs= p; 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 <albert@cs= ail.mit.edu>
> To: BlueZ users <bluez-users@lists.sourceforge.n= et>
> Sent: Monday, November 13, 2006 11:33:52 AM
> Subject: Re: [Bluez-us= ers] Multiple Bluetooth adapters question
>
>
> You shoul= d 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.
><= BR>> -albert
>
> On 11/13/06, Brown Dwarf <brown_drf@yaho= o.com> wrote:
> >
> > Hi all,
> >  =     This may be a FAQ, but I could not locate an defini= t answer.
> >
> > I want to what are all the implications= of having multiple bluetooth
> > adapters on a machine.
> &= gt; 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<= BR>> 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 t= he 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 y= our job
> > easier
> > Download IBM WebSphere Application Se= rver v.1.0.1 based on Apache Geronimo
> >
> http://sel.as-us.falkag.net/sel?cmd=3Dlnk&= ;kid=3D120709&bid=3D263057&dat=3D121642
> >
> &g= t; _______________________________________________
> > Bluez-users= mailing list
> > Bluez-users@lists.sourceforge.net
> > <= A href=3D"https://lists.sourceforge.net/lists/listinfo/bluez-users" target= =3D_blank>https://lists.sourceforge.net/lists/listinfo/bluez-users
&= gt; >
> >
> >
>
> ------------------------= -------------------------------------------------
> 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=3Dlnk&a= mp;kid=3D120709&bid=3D263057&dat=3D121642
> _____________= __________________________________
> Bluez-users mailing list
>= Bluez-users@lists.sourceforge.net
> https://lists.sourcefo= rge.net/lists/listinfo/bluez-users
>
>
>
> ----= ---------------------------------------------------------------------
&g= t; Using Tomcat but need to do more? Need to support web services, security= ?
> Get stuff done quickly with pre-integrated technology to make you= r job
> easier
> Download IBM WebSphere Application Server v.1.= 0.1 based on Apache Geronimo
> http://sel.as-us.falkag.net/sel= ?cmd=3Dlnk&kid=3D120709&bid=3D263057&dat=3D121642
>> _______________________________________________
> Bluez-users = mailing list
> Bluez-users@lists.sourceforge.net
> ht= tps://lists.sourceforge.net/lists/listinfo/bluez-users
>
><= BR>>

------------------------------------------------------------= -------------
Using Tomcat but need to do more? Need to support web serv= ices, 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=3Dlnk&kid=3D120709= &bid=3D263057&dat=3D121642
_________________________________= ______________
Bluez-users mailing list
Bluez-users@lists.sourceforge= .net
https://lists.sourceforge.net/lists/listinfo/bluez-users<= /A>
=0A


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