Posted: Thu Sep 07, 2006 14:44 Post subject: low data rate in WDS mode
Hi all,
I've a problem regarding data rate with two WRT54GL v1.1 with DD-WRT v23 SP2 (08/30/06) std.
WRT#1<---->WRT#2
Configuration is identical for both of them: AP, WDS, CH1, power 125mW, WPA-PSK-AES key interval 3600sec, transmission rate auto.
Signal is very good, -52 at both ends on a 4Km link, and there are no RX/TX errors:
WRT#1
Received (RX)1175357 OK, no error
Transmitted (TX)1265502 OK, 3149 errors
WRT#2
Received (RX)1346685 OK, no error
Transmitted (TX)1237950 OK, 4515 errors
It seems that there is no interference, because of no Tx/Rx errors.
Despite all the above, the two WRTs connects at a data rate of only 5.5Mbps , and the link net throughput is 2,3Mbps. If I try to "force" 11Mbps or higher, errors occours and net throughput goes down.
Along the lines of the last post... You can use channels 12-13 for WDS but your USA wireless clients may not attach.
In addition to the ideas above:
1) run wrtbwlog to find the "cleanest channel"
2) rotate and/or tilt the antennas on one router relative to the other, to maximize the signal and the rate. Rotating one router even 5 degrees can make a big difference.
Joined: 17 Jul 2006 Posts: 96 Location: Austin, Texas USA
Posted: Mon Sep 11, 2006 19:45 Post subject:
Played around with my three routers and about the only setting that dramatically changed speed was transmit power. Anything over 110mw degraded performance.
At 110mw it's 54mps on all routers....140mw went down to 36 mps, over 160mw all over the place on the lower end, at 180mw or more it was barely hanging in.......
Joined: 06 Jun 2006 Posts: 3763 Location: I'm the one on the plate.
Posted: Mon Jul 07, 2008 14:29 Post subject:
Your problem is the ACK timing. Reflash with DD-WRT V23 SP1 and set the ACK to the correct values. You will link at about 48 Mbps with a -52 signal. _________________ http://69.175.13.131:8015 Streaming Week-End Disco. Station Ripper V 1.1 will do.
Joined: 06 Jun 2006 Posts: 3763 Location: I'm the one on the plate.
Posted: Tue Jul 08, 2008 8:58 Post subject:
VTCop wrote:
Some other way to try this?
That is the way. You do not need to experiment. You need to set the ACK timing value for the correct distance plus about 5%. When you have the correct value then your data delivery rate will be the same as when you have a local link. It will only be limited by your signal strength and signal to noise ratio. I use Q-Check to test my links for proper power settings and ACK timing.
If you are using the Buffalo WHR-HP-G54 model of radio you should enable the receiver pre-amp with board flag settings of 0x2758. I use these same radios for my 4 mile WDS link and enabling the pre-amp gives about 12 dB of RX boost and a higher connection rate.
Joined: 06 Jun 2006 Posts: 3763 Location: I'm the one on the plate.
Posted: Tue Jul 08, 2008 11:57 Post subject:
VTCop wrote:
Enable the pre-amp, Doesn`t increase the SNR?
Thanks
It actually decreases the signal to noise ratio. In other words, it will add a small amount of noise to the signal that was not in the signal before. In most cases the benefit of improving your own signal results in a higher link rate and better data quality. Remember that all radio receivers are already a string of high gain amplifiers in series. That is what a radio is, one big string of amplifiers and frequency converters. The HP model simply has an extra booster stage that other radios do not have. That is exactly why you need to use Q-Check to see how much bandwidth your link can carry, and then start tuning your radio system and ACK value for optimal throughput. _________________ http://69.175.13.131:8015 Streaming Week-End Disco. Station Ripper V 1.1 will do.
, and the link net throughput is 2,3Mbps. If I try to "force" 11Mbps or higher, errors occours and net throughput goes down.
