Re: UBNT XR-9 versus XR-5 performance not as good evenw/ LOS

Brett-

Thanks a bunch for the reply.  I will stick with the 20mhz channels so I can
stick w/ 0.9.4 madwifi which has worked well for me (so far w/ XR5, XR2, SR2,
SR5 and CM-9 radios I use)

It sounds like my issues are mostly noise.  I don't have a spectrum analyzer,
but the UBNT airview 9 looks tempting.
I thought it may have been poor antennas or the way in which madwifi configures
the hardware that made my XR9 radios do poorly compared to XR5.

I will try again w/ a pair of superpass panels out in the country to see if i
can get w/ LOS some decent performance.  Then, possibly with the aid of an
airview 9, I can take another look at the Cambridge area.

Since the XR9 can work w/ 20 mhz channels, then this also means I can try the
XR7.  The thought is the 700 band will be much less crowded.  I didn't want to
keep working with the UBNT lower frequency cards if some fundemental problem w/
using them with madwifi would make them not work well, but that sounds like it's
not the case if one can use 20mhz bandwidth channels.

My problem is we have a few areas that are somewhat non-los and it would be nice
to use 900 or 700 to get through those areas.  We've got other areas with LOS or
just a small tree branch or two and XR5 radios do fantastic.  It would nice to
do a hybrid of 5 ghz and 900 or 700 mhz to get to where I want to be.  So far
the 900 stuff has been a no-go, but I didn't want to give up just yet.

-Eric






> Hi,
>
> The XR9 will only ever use the 20MHz channels with madwifi, unless you
> hack the source code. One problem with a 20MHz wide channel at 900MHz is
> there are a lot of frequency hopping radios around that use that ISM
> band also. They will surely degrade your throughput.
>
> In the case of noise from frequency hoppers, you are better off with the
> 10 or 5MHz channels, because a lot more of the hopping frequencies will
> be outside of your band.
>
> Which brings me to another problem I have struggled very long and hard
> with. The channel noise reading for madwifi does not represent the
> actual background RF energy on the channel. There is really very little
> publicly available information on this topic, so let me give a quick
> example of what I mean. I set up a test where I monitored the 900MHz
> band used by the XR9 using a spectrum alalyzer. I could clearly see RF
> interference with a signal level of -60dBm, however an XR9 reported only
> -92dBm channel noise.
>
> I would really love to know for certain that it is just not possible for
> the atheros hardware to provide a true reading of channel noise? This
> really is a very major problem, as you are finding out, if you cannot
> accurately measure the channel noise then how can you accurately asses
> the viability of your radio path (other than just noting that the
> throughput one achieves is miserable given the signal strength).
>
> Can anyone out there help shed any more light on this issue?
>
> Brett
>
>> -----Original Message-----
>> From: Eric Malkowski [mailto:[email protected]]
>> Sent: Tuesday, 9 February 2010 5:56 AM
>> To: [email protected]
>> Subject: [Madwifi-users] UBNT XR-9 versus XR-5 performance not as good
>> evenw/ LOS
>>
>> I posted this over on Ubiquiti's forum, but I'm confident a lot of you
>> subscribed here use UBNT's cards for various things.
>> So I'm posting this here to see what advice any of you w/ experience
>> might have to offer.
>>
>> I have several UBNT radios including XR2, SR2, XR5, SR5, and XR9
>> All of my 2 and 5 ghz radios work fantastic w/ 2.6.29.X kernel and
>> Madwifi 0.9.4 release. I think it's because they work fine w/ default
> 20
>> mhz channels (up to 54 Mbps) etc.
>> I use Pac-wireless (LAIRD) OD24-9 and OD24-7 along w/ OD58-12 and
> their
>> Backfire dish ES58-17 and also Superpass panel antennas for AP and
>> backhaul setups.
>> I've also used LAIRD's mesh series OD58-12M and OD24-7M that attach
>> nicely to an N-female bulkhead connector right on the enclosure.
>>
>> My XR-9's are marginal in the Boston area (Cambridge) and somewhat Ok
>> out in the country.
>> I have a couple cheaper hyperlink yagi antennas for testing HG909Y-NM.
>>
>> I realize XR9 cannot have the channel width set when using regular
>> madwifi and it appears ubiquiti's radio driver is no longer developed.
>> So my question is: What is the proper way to use the XR9 with Madwifi
>> 0.9.4 or the Madwifi current trunk (which includes the now opensource
>> HAL since madwifi-free was merged to the trunk).
>>
>> My guess is since channels 5 and 6 support 5/10/20 mhz width (these
> are
>> 912 Mhz and 917 Mhz center frequencies respectively) then just using
>> Madwifi 0.9.4 to set it up on channel 5 or 6 as AP, adhoc, station,
> etc.
>> with proper tx and rx antenna settings to the single MMCX connector
>> would get me standard 20mhz channel width? I'm fine with that and
>> avoiding channels 4 and 7 since the card can't do 20mhz operation on
>> those.
>>
>> Here's the conversion chart for the channels:
>>
>> Channel 4 - 2427 = 907Mhz @ 5/10 Mhz bandwidth
>> Channel 5 - 2432 = 912Mhz @ 5/10/20Mhz bandwidth
>> Channel 6 - 2437 = 917Mhz @ 5/10/20Mhz bandwidth
>> Channel 7 - 2442 = 922Mhz @ 5/10 Mhz bandwidth
>>
>> Next question: Would going to the madwifi trunk buy my anything in
> terms
>> of functionality? i.e. would I possibly be able to set channel
> bandwidths?
>>
>> In my testing if I remember correctly using channel 5 or 6 out in the
>> country w/ a couple houses and dense pine trees (no line of sight)
> 1000
>> ft apart I would get -65 signal on each end and about 18 megabit rate.
>> In Boston w/ clear line of sight w/ the same setup about 2000 feet
> apart
>> I could only get about -75 on each end w/ only a ping or two. I don't
>> remember the reported noise floors.  I'm wondering if only doing the
> 18
>> megabit rate is an indicator that the card is only doing 10 mhz width
>> due to default settings madwifi 0.9.4 uses.  With -65 signal and
> better
>> on XR2 or XR5 cards, I can easily do higher rates (36 48 54 Mbps).  I
>> don't think there should be too much noise around since we were along
>> the Charles river in Cambridge just shooting across the water at
>> constant elevation and away from the very dense buildings in Boston
>> downtown proper.
>>
>> I read on UBNT forums also in past posts I think Mike Ford had
> mentioned
>> pac wireless antennas were one of his favorites for XR9 -- they are
> one
>> of my favorites for XR2 and XR5 but I haven't tried anything but the
>> cheap hyperlink yagis. I also read someone likes Superpass (which I
> also
>> like their panels for 2.4 ghz stuff) and I could try those.  It's
>> unclear if it's an antenna issue, noise, or the card be driven in a
> way
>> it's not meant to be by stock madwifi 0.9.4
>>
>> But before I try more antennas and go any further with XR9 (or XR7
> which
>> I have been looking at and wondering about) I wanted to know what I
>> could expect and how to properly use the XR9 with Madwifi 0.9.4 latest
>> release (which is still binary HAL) or with Madwifi trunk. I'm hoping
> I
>> can just set one of the two 20mhz supporting channels and enjoy using
> it
>> -- but an XR5 w/ similar line of sight with similar gain antennas (and
>> not even directional on one but rather omni one end and backfire dish
>> the other end) can get signal of -50 or better on both ends w/ easy 48
>> or 54 Mbps rates on 2000' line w/ LOS in Cambridge along the charles
>> river (same beam path as the XR-9s).
>>
>> If I cannot expect to reliably use madwifi 0.9.4 or madwifi trunk w/
> the
>> XR9, then what should I use and where are directions to be able to set
>> channel widths w/ some type of known working driver (modified Madwifi
> or
>> UBNT radio driver) that will work on recent 2.6 linux kernels on x86
>> hardware. (I use PC engines Alix boards that are designed to tolerate
>> the high powered radios of UBNT -- specifically the D series like 3D2
> or
>> 2D3.
>>
>> Any advice would be appreciated.
>>
>> Sorry for the long winded message.  I like to include details.
>>
>> -Eric Malkowski
>>
>>
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