2009/11/25 Benoit PAPILLAULT <benoit.papilla...@free.fr>: > Benoit PAPILLAULT a écrit : >> >> TX rate is dropping a lot (like 20 MBits down to 200 kbits/s). Using >> another card in monitor mode, I still see packets sent at 54 Mbits rate >> however. >> >> > > I found out what is wrong with the TX throughput. In fact, when a packet is > transmitted at 54 Mbits, the destination send back a 802.11 ACK which is > ignored!!! As such, the packet is transmitted at 54 Mbits once again, then > twice at 48 Mbits, then twice at 36 Mbits ... and so on down to 1 Mbits. Of > course, this divide the throughput by 18 (twice for each 9 rates), leading > to 200 - 300 kbits. > > When implementing proper TX status reporting, needed by minstrel rate > control, I also found out that some 802.11 ACK where not received by the > driver, but received by the card, leading to inconsistencies in the rate > control code. > > Are there some registers that are responsible for ACK behavior? > > Regards, > Benoit > >
ACK handling and retrying is one of the known weak points of the zd1211(b) chipset - apparently enabling CR_SNIFFER causes the card to ignore ACKs received. Also, the retry plan for unACKed outgoing packets (retry count & rates) needs to be uploaded to the device on firmware init, and can't be controlled per-packet. Luis: Any chance of an open firmware release for the ZD1211, similarly to what was done for AR9170/ZD1221? That would probably allow for fixing these problems. -- Vista: [V]iruses, [I]ntruders, [S]pyware, [T]rojans and [A]dware. :-) ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Zd1211-devs mailing list - http://zd1211.wiki.sourceforge.net/ Unsubscribe: https://lists.sourceforge.net/lists/listinfo/zd1211-devs
