Maximizing 802.11b throuput

Ray ray at sonictech.net
Thu Mar 13 15:11:05 EST 2003


On Thu, Mar 13, 2003 at 10:24:44AM -0300, Andr? Luiz Ribeiro Moutinho wrote:
> Hi,
> 
> I am implementing a realtime video streamming application using
> 802.11b in order to transmit video data.
> Transmitting MJPEG 320x240 at 30fps and 40% quality results a 
> 3Mbit/s total bandwith. When I try to increase the video data 
> bandwith (for instance, rising JPEG quality), the radio channel starts
> failing to transmit all video information. I would like to know what
> is the REAL 802.11 data transmittion throuput (4 or 5Mbit/s ??) and
> what could be done in order to maximize the data throuput. For instance,
> trying to optimize the transmitted data block size.
> I need to use the maximum data bandwith available in order to transmit 
> the maximum mount of video sessions possible.

What is your network like, client -> HostAP -> client or something else? 
I'm getting 4 - 4.5 Mbps (as shown by ncftp) going from a computer on my
wired lan to a wireless node via a hostap machine (in AP mode) at the
moment.  My hostap machine is pretty underpowered so there might be a little
room for improvement in my setup.  I was going to suggest setting rts to off
as long as you arn't dealing with any hidden node problems but I just tried
it and it made no difference at all (which suggests something must be wrong
imho).

BTW, I've got a hardware mjpeg capture card and now you've got me curious so
I'll probably try playing live video over my link this weekend if I have
time.  Another option, if you have the cpu for it would be to recompress to
mpeg4 which should be pretty good at half or less the bandwidth of mjpeg.

-- 
Ray



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