[Bluez-users] impact of distance on quality of transmission ?

[Bluez-users] impact of distance on quality of transmission ?

[Alexandre Campo]

Hi,

I am working with a bunch of robots and I communicate with them using bluetooth connections.
I am trying to receive data from 7 robots at the same time.

For this, I simply connect to each robot using a program linked against libbluetooth,
that makes use of sockets and rfcomm.

Using only one robot, we manage to receive pretty well the data.
Using 7 robots things get complicated. If robots are close (~1 meter) from the bluetooth
dongle, we receive all the data.

As soon as the robots are far from the dongle (~2 meters and more) we start observing errors
in the data transmitted.

I am surprised because :
* we do not exceed the bt bandwidth (< 800 kb/s)
* we use SOCK_STREAM sockets that are supposed to be reliable

My questions :
* any idea of what causes these mistakes ?
* how to avoid transmission errors ?


Thanks a lot for your help,
Alexandre Campo.


------------------------------------------------------------------------

Details :
I use a belkin bt usb adapter (100m range)

info from usbview : 

BCM92045DG Non-UHE
Manufacturer: Broadcom Corp
Speed: 12Mb/s (full)
USB Version:  2.00

The robots have 

a bluetooth serial port module :
http://www.national.com/pf/LM/LMX9820A.html#General%20Description

a phycomp 2.45 GHz antenna :
http://www.phycomp-components.com/ (website unavailable ?)


-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys - and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
Bluez-users mailing list
Bluez-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users

Re: [Bluez-users] impact of distance on quality of transmission ?

[Pering, Trevor]

This is strange because Bluetooth implements reliable ACL connections...
We've done multiple-client communications at greter range... a couple of
questions come to mind.

What about 3 roots?  5? When you see "pretty well the data" -- are there
ANY errors?  There really shouldn't be.

What profile are you using?  PAN?

How do the errors manifest themselves?  Is this using standrd linux
socket calls? How many errors do you see?

What BT hardware are you using?

	Trevor


>-----Original Message-----
>From: bluez-users-bounces@lists.sourceforge.net 
>[mailto:bluez-users-bounces@lists.sourceforge.net] On Behalf 
>Of Alexandre Campo
>Sent: Tuesday, November 21, 2006 2:30 PM
>To: bluez-users@lists.sourceforge.net
>Subject: [Bluez-users] impact of distance on quality of transmission ?
>
>Hi,
>
>I am working with a bunch of robots and I communicate with 
>them using bluetooth connections.
>I am trying to receive data from 7 robots at the same time.
>
>For this, I simply connect to each robot using a program 
>linked against libbluetooth,
>that makes use of sockets and rfcomm.
>
>Using only one robot, we manage to receive pretty well the data.
>Using 7 robots things get complicated. If robots are close (~1 
>meter) from the bluetooth
>dongle, we receive all the data.
>
>As soon as the robots are far from the dongle (~2 meters and 
>more) we start observing errors
>in the data transmitted.
>
>I am surprised because :
>* we do not exceed the bt bandwidth (< 800 kb/s)
>* we use SOCK_STREAM sockets that are supposed to be reliable
>
>My questions :
>* any idea of what causes these mistakes ?
>* how to avoid transmission errors ?
>
>
>Thanks a lot for your help,
>Alexandre Campo.
>
>
>---------------------------------------------------------------
>---------
>
>Details :
>I use a belkin bt usb adapter (100m range)
>
>info from usbview : 
>
>BCM92045DG Non-UHE
>Manufacturer: Broadcom Corp
>Speed: 12Mb/s (full)
>USB Version:  2.00
>
>The robots have 
>
>a bluetooth serial port module :
>http://www.national.com/pf/LM/LMX9820A.html#General%20Description
>
>a phycomp 2.45 GHz antenna :
>http://www.phycomp-components.com/ (website unavailable ?)
>
>
>---------------------------------------------------------------
>----------
>Take Surveys. Earn Cash. Influence the Future of IT
>Join SourceForge.net's Techsay panel and you'll get the chance 
>to share your
>opinions on IT & business topics through brief surveys - and earn cash
>http://www.techsay.com/default.php?page=join.php&p=sourceforge&
CID=DEVDEV
>_______________________________________________
>Bluez-users mailing list
>Bluez-users@lists.sourceforge.net
>https://lists.sourceforge.net/lists/listinfo/bluez-users
>

-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys - and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
Bluez-users mailing list
Bluez-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users