[Madwifi-devel] Disable link layer retransmissions in ARQ

Discussion:

Vighnesh Rege

2011-04-29 04:45:20 UTC

Hey guys,

I am currently working on a video transmission project that requires me to
transmit video data over a wireless channel and characterize the bit errors
observed.
So, I need to turn off CRC, link layer retransmissions and any other
error-control protocol. I managed to turn off CRC by modifying a
/proc/sys/net entry.

Now I need to turn off link layer retransmissions. Any advice in this matter
would be highly appreciated!

Thanks
Vighnesh

Abhijeet Bhorkar

2011-04-29 17:13:17 UTC

Permalink

You need to treat the packet like a broadcast packet. So, any packet should
behave like a broadcast (this will
remove the retransmissions)
though with specific information of next hop/ and next hop mac keeking the
same as original.

You need to go in detail for the driver.
There is a function called ath_tx_start in the file if_ath.c.
Consider the code which says IEEE80211_FC0_TYPE_DATA:.
Set try0 = ATH_TXMAXTRY for all the packets. Note that try0 is already set
to that value when the
packet is broadcast (or ismcast). You need to change the code for other
packets.

Abhijeet

Post by Vighnesh Rege
Hey guys,
I am currently working on a video transmission project that requires me to
transmit video data over a wireless channel and characterize the bit errors
observed.
So, I need to turn off CRC, link layer retransmissions and any other
error-control protocol. I managed to turn off CRC by modifying a
/proc/sys/net entry.
Now I need to turn off link layer retransmissions. Any advice in this
matter would be highly appreciated!
Thanks
Vighnesh
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Vighnesh Rege

2011-05-02 06:28:17 UTC

Permalink

Hey,

Thanks, Abhijeet, for your recommendation. Before looking into the source
code, I tried checking if I could turn off retransmissions on my laptop,
which uses a proprietary Intel driver. The command *sudo iwconfig wlan0
retry 0 *worked and I used my laptop as the transmitter.

The same command does not work for Madwifi, though. So if I wish to use a
Madwifi-equipped computer as a transmitter, I guess I'll have to look into
the source code.

Regards
Vighnesh

On Fri, Apr 29, 2011 at 10:13 AM, Abhijeet Bhorkar <

Post by Abhijeet Bhorkar
You need to treat the packet like a broadcast packet. So, any packet should
behave like a broadcast (this will
remove the retransmissions)
though with specific information of next hop/ and next hop mac keeking the
same as original.
You need to go in detail for the driver.
There is a function called ath_tx_start in the file if_ath.c.
Consider the code which says IEEE80211_FC0_TYPE_DATA:.
Set try0 = ATH_TXMAXTRY for all the packets. Note that try0 is already
set to that value when the
packet is broadcast (or ismcast). You need to change the code for other
packets.
Abhijeet

Abhijeet Bhorkar

2011-05-02 06:38:49 UTC

Permalink

Yes. Madwifi code is broken for iwconfig retry command. There are
some updates available on net to fix it. But I am not sure, if you
can get the updates
correctly for the version you use. I think ath5k has the correct
code. If you can switch to ath5k, it would be more helpful to you,
since it is the most updated code.

Abhijeet

Post by Vighnesh Rege
Hey,
Thanks, Abhijeet, for your recommendation. Before looking into the source
code, I tried checking if I could turn off retransmissions on my laptop,
which uses a proprietary Intel driver. The command *sudo iwconfig wlan0
retry 0 *worked and I used my laptop as the transmitter.
The same command does not work for Madwifi, though. So if I wish to use a
Madwifi-equipped computer as a transmitter, I guess I'll have to look into
the source code.
Regards
Vighnesh
On Fri, Apr 29, 2011 at 10:13 AM, Abhijeet Bhorkar <