Re: [Madwifi-users] 15 mile XR5 5Ghz link with two 29dB dishes - great link - poor throughput
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From: Derek C. <de...@ri...> - 2008-01-15 00:40:21
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Hi again Aidan, I was re-reading your email again. I'll have to try out the coverageclass command and see what happens. I wish I'd tried this before swapping the boards because now I don't have a long distance link ready to test - but I'll give it a go for sure and I'll report back to the list! thanks again, Derek On Mon, 2008-01-14 at 23:28 +0000, Derek Conniffe wrote: > Hi Aidan, > > Thats very interesting (not least the use of the 8 Ghz band - I need to > look at up to see what's happening at 8Ghz in Ireland). > > I've been using the Ubiquity XR5 cards - they have a built-in amp and > have an "offset" whereby they report a lower dBm power to madwifi (I > think the offset is 8 so a reported 17dBm actually equals 25dBm) - an > apparently great way to step around the regdomain / country code thing. > > Now I'm sure its some kind of timing problem in madwifi. At 15 miles > (between the data centre and the mountains) I was getting great signals > with 29dBi solid dishes (the low 60s for signal level and up to 40/94 > link quality) but really poor throughput. > > So I swapped the boards for Ubiquity Litestation5s (router boards with > their 400mW 5Ghz boards built-in and a web interface). I'm getting the > same signal levels but I'm getting around 20Mbits over the 15mile link > (simplex I think - the standard iperf tests) - I'm writing this email > now at home on 20mbits over two hops (23 miles and only 5ms latency) > from the data center which is in west Dublin (I'm in the neighbouring > county of Wicklow) - quite amazing really considering that my neighbours > and I can't even get ISDN never mind DSL!. > > I've seen the same problem in the last couple of days too. Yesterday I > made another madwifi 5Ghz link 8 miles or so from the mountain to my > house and the link was jumping between around 13Mbits and 600kbits (one > or the other - not in-between) although the signal levels hadn't changed > (they were looking good as usual). Actually I was using madwifi and an > XR5 as the AP and a Litestation5 as the STA and this problem happened. > This morning I replaced the madwifi board with another Litestation5 and > an iperf test right now is showing 23.8Mbits/sec. > > I have other smaller links (up to 7 miles) where I'm getting great > throughput with madwifi, PC engines boards, XR5s and madwifi. > > Its as if there is some limit (around 8 miles it looks like) where > suddenly a timing problem (it looks like a too-low ack rate) appears > (but I have the ack rate up and I can see that in the /proc.... setting > for the wifiX card). > > Its a problem because I'd much rather be able to use madwifi (for all > the other bits of software I've written in perl that I like to run on > the boards) and while the Litestation5s are great I'd much rather see > them as CPEs only. > > thanks for the help though - I hope sometime I'll know whats really up! > > Derek > > > On Mon, 2008-01-14 at 17:12 +0000, Aidan Walton wrote: > > Hi Derek, > > I have similar set-up here in England where I serve rural areas > > broadband using 8.750GHz and above (Band C). I never used the athctrl > > command. Instead I bring the interfaces up using: > > > > iwpriv ath0 coverageclass 20 > > > > I can confirm that this makes a huge difference to throughput. I was > > testing an 11km link without setting the coverageclass variable and > > throughput was awful. Setting as above and I can get 30Mb/s over the > > link. I assume the variable relates to uS propagation time. However > > after many attempts to find some information about this I gave up and > > assumed I was correct. Anyway it works. > > All the best > > Aidan > > > > > > On Mon, 2008-01-07 at 20:56 +0000, Derek Conniffe wrote: > > > Hi all, > > > > > > I've had a good time setting up a 15 mile point-to-point link with two > > > 29dB parabolic dish antennas and Ubiquity XR5 802.11a cards. > > > > > > The link stats look great with iwconfig - right now its reading -50 > > > signal, -94 noise and 44/94 link quality. I'm at 5.18 Ghz. > > > > > > I'm using Voyage linux (0.4.1). > > > > > > Whats funny is that my data throughput is really poor - iperf keeps > > > giving me around 600 kbps. Typing with ssh feels fine and pings are > > > really good at around 1.5 ms. > > > > > > I've tried playing around with athctrl -d and I've found that a distance > > > of 13,000 seems to give the highest throughput - a figure of 20,000 > > > seems to lower my throughput to around 400kbps. > > > > > > I have another new link up of around 7 miles and with badly aimed lower > > > gain antennas I'm getting around 13Mbps. > > > > > > Is there some other settings that I should alter other than just using > > > the athctrl command? > > > > > > This 15 mile link is over a city (although very directional antennas) > > > and I don't see other 802.11a APs with iwlist scanning. I'm not sure if > > > there is other interference out there (although noise looks very low). > > > At 5.8 Ghz the noise is higher (-87) and throughput is much the same. > > > > > > Any help would be great > > > > > > thanks very much, > > > > > > Derek > > > > > > > > > ------------------------------------------------------------------------- > > > Check out the new SourceForge.net Marketplace. > > > It's the best place to buy or sell services for > > > just about anything Open Source. > > > http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace > > > _______________________________________________ > > > Madwifi-users mailing list > > > Mad...@li... > > > https://lists.sourceforge.net/lists/listinfo/madwifi-users > > > > > ------------------------------------------------------------------------- > Check out the new SourceForge.net Marketplace. > It's the best place to buy or sell services for > just about anything Open Source. > http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace > _______________________________________________ > Madwifi-users mailing list > Mad...@li... > https://lists.sourceforge.net/lists/listinfo/madwifi-users |