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<DIV><SPAN class=432265913-13032003><FONT face=Arial color=#800000
size=2><STRONG>In theory the overal bit rate would be not so far from 11
Mbits. If I'm not wrong, based on payload size of 1500 bytes, a total overhead
of 1148 bytes max (including PHY (guard interval + 1Mbit/s
overhead) , MAC (DFIS + data frame header), LLC header, SNAP header , IP
header, UDP header) would give you a total throughput of 7.8 Mbit/s.
</STRONG></FONT></SPAN></DIV>
<DIV><SPAN class=432265913-13032003><FONT face=Arial color=#800000
size=2><STRONG>This is for one way streaming in multicast/broadcast without any
IEEE802.11 association attempt (no uplink traffic at all) and good channel
quality. </STRONG></FONT></SPAN></DIV>
<DIV><SPAN class=432265913-13032003><FONT face=Arial color=#800000
size=2><STRONG></STRONG></FONT></SPAN> </DIV>
<DIV><SPAN class=432265913-13032003><FONT face=Arial color=#800000
size=2><STRONG>In multicast however I've constated that the bit rate is sometime
limited by the firmware of my card (PCI prism2 Linksys). I cannot stream more
than 1Mbit/s. </STRONG></FONT></SPAN></DIV>
<DIV><SPAN class=432265913-13032003><STRONG><FONT face=Arial color=#800000
size=2></FONT></STRONG></SPAN> </DIV>
<DIV><SPAN class=432265913-13032003><STRONG><FONT face=Arial color=#800000
size=2>If you stream in unicast this is another story. MAC acknowledgment
may reduce considerably the bandwidth depending on the quality of your channel.
Practically the 3Mbit/s number seems often raised.
</FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=432265913-13032003><STRONG><FONT face=Arial color=#800000
size=2> </FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=432265913-13032003><STRONG><FONT face=Arial color=#800000
size=2>In theory transmitting in multicast with the maximum packet size is
the way to maximize the bandwidth usage. However you have to cope in some way
with error correction. </FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=432265913-13032003><STRONG><FONT face=Arial color=#800000
size=2></FONT></STRONG></SPAN> </DIV>
<DIV><SPAN class=432265913-13032003><STRONG><FONT face=Arial color=#800000
size=2>Guillaume Bichot</FONT></STRONG></SPAN></DIV>
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<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B> André Luiz
Ribeiro Moutinho [mailto:andre.moutinho@compsisnet.com.br] <BR><B>Sent:</B>
Thursday, March 13, 2003 8:25 AM<BR><B>To:</B> hostap@shmoo.com<BR><B>Cc:</B>
Mauricio Micoski; Marcelo Ferreira Vinhas; Marco Antônio
Fernandes<BR><B>Subject:</B> Maximizing 802.11b throuput<BR><BR></FONT></DIV>
<P><FONT face=Arial size=2>Hi,</FONT> </P>
<P><FONT face=Arial size=2>I am implementing a realtime video streamming
application using</FONT> <BR><FONT face=Arial size=2>802.11b in order to
transmit video data.</FONT> <BR><FONT face=Arial size=2>Transmitting MJPEG
320x240@30fps and 40% quality results a </FONT><BR><FONT face=Arial
size=2>3Mbit/s total bandwith. When I try to increase the video data
</FONT><BR><FONT face=Arial size=2>bandwith (for instance, rising JPEG
quality), the radio channel starts</FONT> <BR><FONT face=Arial size=2>failing
to transmit all video information. I would like to know what</FONT> <BR><FONT
face=Arial size=2>is the REAL 802.11 data transmittion throuput (4 or 5Mbit/s
??) and</FONT> <BR><FONT face=Arial size=2>what could be done in order to
maximize the data throuput. For instance,</FONT> <BR><FONT face=Arial
size=2>trying to optimize the transmitted data block size.</FONT> <BR><FONT
face=Arial size=2>I need to use the maximum data bandwith available in order
to transmit </FONT><BR><FONT face=Arial size=2>the maximum mount of video
sessions possible.</FONT> </P>
<P><FONT face=Arial size=2>Thanks a lot,</FONT> </P>
<P><FONT face=Arial size=2>Andre Moutinho </FONT></P></BLOCKQUOTE></BODY></HTML>