Re: [Madwifi-users] 15 mile XR5 5Ghz link with two 29dB dishes - great link - poor throughput

[Aidan W. <aw...@wi...>]

Derek,
A slip of the keyboard I'm sure you realise. I am using 5.8GHz but in
the licensed section here in the UK. That is between 5.725 - 5.850 GHz.
I too use SR5 cards and I must say most of my links are much shorter
than yours. 

The one reference I have for longer distances came last summer when I
ran an 11km link at 30Mb/s after setting coverage class. Before changing
the coverage class I was only getting 400kb/s.

You are doing well with your link qualities though. I get much lower
signal quality but I am typically skimming the top of local hills or
houses. It makes a huge difference (Fresnel Zones I assume). As always
with radio there is no substitute for antenna height! I imagine with one
end in the mountains and the other in the town you have a good clear
view of the two ends.

Good luck!
Aidan

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
> >