Mostly, I'm just bringing up conversation. But to be more specific...
I'm referring to Multipath as reflection building mounted on.
I have not had any problems with my 18Ghz links yet. But I have plans to
install a larger number of them that have limited mounting space, which has
significant investment at stake. The antennas will likely need to be mounted
back against a brick wall, pointing 45 degrees or so from the wall. This
created the possibilty of reflection off the wall.
If you read Dragon Wave's installation guides, you will see that they bring
attention to the risks of multi-path reflection specifically for 18Ghz. (Or
maybe I'm getting it confised with 24Ghz). They are suggesting mounting the
antenna signifcantly higher off the roof line, than would be typical of a
5.8Ghz installation for example. Based on their diagrams it would infer that a
3ft dish on a 5 foot pole would not be wise. Preferrably mounting more like
antenna center at 7-8 feet off roof line. These number are not exact text
taken out of the guide, just pulled out of my head. A wall, would have the
same effect as a roof surface except worse as the brick is more reflective than
gravel with tar underneight.
I'd like to point to an example with 60Ghz. We recently have ran into cases
and seen cases where, a small puddle of water on the roof surface has destoyed
a link, eventhough the antenna was 10feet off the roof line. We have seen a
Building roof edge wall with a 1ft flat surface, 30 feet away and 10 feet
lower, and had it create a multipath reflection that has killed the link. We
have seen cases where to steep of an angle looking down has made it impossible
to get a good link to ever work in the first place. Installers will swear that
the radios are bad, or fight with it for days, only to learn after the fact one
just needed to misalign away from the harmful reflection, once identified where
it was. And it often comes from places one would never imagine. See Puddle of
water example. Its really a different animal altogeather. I'm not saying that
18Ghz has anywhere near the risks or pickyness as 60Ghz. I'm just trying to
get feedback, to prevent any surprises. (PS. Some peop
le refer to 18Ghz and up as Millimeter Wave instead of Microwave).
If I need to mount above a penthouse roof line, I need to plan for that. There
are windload issues for 3ft dishes. If I can mount on the wall below the
penthouse roof line, it makes it much easier. Antennas can blend into wall,
when painted. They don't blend in sticking up over the roof. In our area,
anything over 3 miles really needs a 3ft dish, for carrier equivellent
reliabilty. I'm concerned on whether we can get away with 2ft dishes on the
2.5 mile links, at top reliabilty. I think, I can. But when you are providing
a mission critical link to a data center, 10 minutes of downtime is huge. And
time for experimentation is not after its live.
In our market, there is a big reoccuring cost difference between a 3ft and a 2
ft dish. I may not be able to fit qty 2- 3ft dishes on a pole, but I can fit 2-
2ft dishes on a pole. And that Pole may be costing me $300to $500 per month. I
want to use 2ft when I can.
I'm probably making more of this, than I need to, but I'm planning on doing a
lot of links at once, and I'd rather not go back, and redo them all after the
fact because I guessed wrong.
Some of the Path Calculators are misleading. The reason is they have you insert
a rain zone, off the chart for either 4-9s or 5-9. But then when they give you
the results of the calculation, it is given in Number of 9's reliabilty. Which
doesn't make sense. Let me explain... We are going to try to Calculate Max
distance for a specific reliabilty. Lets say D2 rain zone 4-9 (99.99) is: 48,
but then for 5-9 its 112. Do the path calcs with 4-9 (48), varying the
distances until the results are 5-9 of reliabilty. Then do path Calcs with 5-9
(112), varying distance until get results of 4-9 reliabilty. The Link Distances
are way different. Then repeat path Calcs 4-9 (48) varying distance until get
4-9 reliabilty, and then repeat path calc for 5-9 (112) varying distance until
get results of 5-9. The link distances are even more drastically different. If
someone wants 4-9 or 5-9 reliabilty, what results does one trust to make that
determination? You'll see that it will have a d
ifference of atleast one dish size, depending on what you want to trust.
You can enter rain fall of 48, and calculate number of 9s, but its not accurate
because a percentage of time is rain fall of 112. And you'll ilikely have worse
results than calculated. You coukd use rain fall of 112, but then it would be
overly restrictive, considering usually the rain fall isn't 112, and you'd have
more uptime than predicted. So the answer is somewhere in between. In order to
report path Calc result in Number of 9's, it should consider this situation and
calculate results somewhere in between.
Considering D2 Rain Zone...
Its pretty certain that for 3.5miles, I'd want 3ft dishes.
Its pretty certain that for 2 miles I'd want 2ft dishes.
But for 2.5-3 miles, its uncertain.
NOw I've done the path calcs, and I've has others more experienced than me run
the path Calcs, for there recommendations. But what I'm looking for is what the
users in the field found, after running their path Calcs. Did their Link go
down in the thunderstorm? And was it a little overengineered or little
underengineered?
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: Travis Johnson
To: WISPA General List
Sent: Thursday, January 17, 2008 5:02 PM
Subject: Re: [WISPA] 18Ghz multi-path
Tom,
Your rainzone affects potential signal loss during a heavy storm... so it
takes a bigger dish or more power to compensate for that... just the same as my
mountaintop towers that get up to 2 feet of ice build-up on them... we have to
plan for 10db of "extra" signal loss during 3-4 months of the year.
I guess I'm not sure why all the questions about multi-path, etc.? I've
_never_ heard of someone not being able to get an 18ghz link working. It's
licensed, so there are no noise issues. It's a tight beamwidth, and if
engineered and installed correctly (not on anything that will move or flex), it
will work.
Is there a particular install you are considering?
Travis
Microserv
Tom DeReggi wrote:
Good info, to build confidence, but, your area is dry climate.
Its a different animal here in our East coast D2 rain zone.
Anyone with D2 zone or worse, Feedback?
We have not seen any multi-path issues with any 18ghz links.
Are you mounted on tenant buildings, towers, or hills?
Multipath would only likely be a concern for tenant building roof mount.
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: Travis Johnson
To: WISPA General List
Sent: Wednesday, January 16, 2008 11:43 PM
Subject: Re: [WISPA] 18Ghz multi-path
Hi,
We currently have five 18ghz links... two have been up for almost 4 years
with less than 30 minutes downtime total.
1 - 7 miles, 2ft dishes, 99.9999% calc'd uptime, so far correct (4 years)
2 - 19 miles, 4ft dishes, 99.999% calc'd uptime, so far correct (4 years)
3 - 14 miles, 2.5ft dishes, 99.999% calc'd uptime, so far correct (8 months)
4 - 15 miles, 2.5ft dishes, 99.999% calc'd uptime, so far correct (8 months)
5 - 28 miles, 2ft dishes, 99.99% calc'd uptime, so far correct (4 months)
We have not seen any multi-path issues with any 18ghz links. We are always
able to get 1-2db better signal than the path calc shows, but it can take a
little time (the 27 mile link took almost an hour to fully align, compared with
10-15 minutes for the other links).
We are in the 12mm/h rain zone.
Travis
Microserv
Tom DeReggi wrote:
So what are you guy finding regarding 18Ghz multi-path.
What we learned over this past year is that multipath for Millimeter Wave
and high Spectrum ranges, is a different animal.
Very picky. 18Ghz specifically is known for negative effects of reflection,
that need to be taken into account in isntalltion design.
Any success rates on wall mounting? Are your links path calc'd for 2ft dish
working with 2 ft, as engineered? Etc.
Are you getting 3- 9s engineering 3- 9's?
This question isn;t about gear, its about 18Ghz.
(Note if mention distance, please mention rain zone)
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: "Chuck McCown - 2" <[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Wednesday, January 16, 2008 12:24 AM
Subject: Re: [WISPA] Looking for short licensed link
I wish we could say the same about the Trango. So far nothing but flaky
behavior and that is with -44 dBm rx signal levels.
But this is a new product to us and there may be something we are not
configuring properly. Not going to count it out until the factory guys
have
had a chance to exhaust their remedies.
----- Original Message -----
From: "Tom DeReggi" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; "WISPA General List" <[email protected]>
Sent: Tuesday, January 15, 2008 10:15 PM
Subject: Re: [WISPA] Looking for short licensed link
The Trango is solid as a rock, also.
Trango is a great product, for a basic config, meaning 1 link, w/ 1
antenna
and radio per side, under 300mbps.
I was nothing but impressed with our units.
Dragonwave currently has the lead from the perspective of supporting all
the
freq ranges in a single paltform, best adaptive modulation routines, and
ability to combine radios on a single antenna to double capacity. But
there
is a price to that. If those feature aren't needed?
Cable Free is also a great product, if you are planning on daisy chaining
several links, the flexibilty and cost savings of these units are
fantastic.
Also very impressed with the overall design of their system. (Only
negative
I found was no adaptive modulation)
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Tuesday, January 15, 2008 11:52 AM
Subject: Re: [WISPA] Looking for short licensed link
Matt
I have installed over 50 Dragonwave links in the past 24 months. 1
outage the result of equipment failure and I had a replacement in my
hand
the next day from Canada.
Airpair goes up to 200 Meg. FD. Horizon will do 600 plus. Multiple IDU.
ODU architecture. You could do 200 MB Horizon for your budget.
I have no experience with the trango.
Bob
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: "Chuck McCown" <[EMAIL PROTECTED]>
Date: Tue, 15 Jan 2008 08:47:10
To:"WISPA General List" <[email protected]>
Subject: Re: [WISPA] Looking for short licensed link
I have used the Trango GigaLink and DragonWave. DragonWave is rock
solid.
Never a problem. Have several systems.
We are still trying to get the Trango to play. Lots of signal but not
running well at all.
----- Original Message -----
From: "Travis Johnson" <[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Tuesday, January 15, 2008 8:44 AM
Subject: Re: [WISPA] Looking for short licensed link
Matt,
I would take a look at the Trango GigaLink 18ghz product. It will do
105Mbps full-duplex (200Mbps total) for your price range and you can do
a software upgrade to 300Mbps full-duplex (600Mbps total) for about
$5,000 extra (at a later date, when you need the speed). It's an
IDU/ODU
setup and you use LMR-400 between them.
You could lease the 600Mbps version on a 36 month, $1 buyout for less
than you are paying for your fiber. ;)
Travis
Microserv
Matt Larsen - Lists wrote:
Hi all,
I am looking for a licensed link to replace a fiber connection. I am
currently paying for a 100meg fiber connection between two of my
towers
and would like to replace it with my own infrastructure. I own the
towers on both sides, there is plenty of LOS and the link distance is
2.9 miles. The connection currently peaks out at about 30 meg, but
I'm
planning to put remote backup servers on the far side, so I'd like to
be
able to maintain 100meg speeds.
I am interested in finding out what kind of radios people are using
for
this type of link. The fiber connection costs me $500/month, and I'd
like to be able to pay for the link within 2.5 years, so that puts a
$12-15K price range on it. Vendors, feel free to contact me
off-list
about this one.
Matt Larsen
vistabeam.com
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