setting up 802.11b to cover a 140,000sq ft warehouse

Hi all, I'm looking for some good recommendations on setting up an
802.11b wlan to coover a warehouse that is roughly 120,000 sq ft in
size. The ceilings are roughly 30ft high and the warehouse is filled
with floor to ceilng racks holding boxed and palletized product. The
purpose of this WLAN is to allow the use of handheld 802.11b scanning
equipment to scan incoming and outgoing shipments into the warehouse
management app. We are currently using wired scanners, which are
located in one area at one end of the warehouse. This makes doing a
full inventory or rescanning pallets very difficult.

Currently I have looked at the 3com MAP's and Wlan switch. These units
seem to cover all of our needs, as they do built in PoE and allow
centralized configuration. The downside is the cost. While I don't
expect this project to be done for free, $2600 for the switch and 300+
each per MAP (estimating roughly 8 MAPS needed) might be a hard sell to
the powers that be.

I've also noticed that D-link makes MAPS and Wlan Switches that also do
PoE. But I'm weary about going with Dlink for something that needs high
availability.

I am aware that I could also go with several standard AP's and
configure them with the same SSID's and Key's and the devices could
just roam between them. I have done this in the past in situations
where mutlipe AP's were needed for coverage reasons and I had no
significant problems. The downside to this is the individual
configuration and lack of integrated PoE for most devices of this
nature. The upside is, naturally, the cost.

Can anyone make some good suggestions on either products or
methodologies to cover what I'm trying to do here? I already have some
good ideas that would accomplish the goal. I"m just looking for
suggestions or ideas from those who may have already ventured down this
road and might have more direct experience.

Thanks!

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> Hi all, I'm looking for some good recommendations on setting up an
> 802.11b wlan to coover a warehouse that is roughly 120,000 sq ft in
> size. The ceilings are roughly 30ft high and the warehouse is filled
> with floor to ceilng racks holding boxed and palletized product. The
> purpose of this WLAN is to allow the use of handheld 802.11b scanning
> equipment to scan incoming and outgoing shipments into the warehouse
> management app. We are currently using wired scanners, which are
> located in one area at one end of the warehouse. This makes doing a
> full inventory or rescanning pallets very difficult.
>
> Currently I have looked at the 3com MAP's and Wlan switch. These units
> seem to cover all of our needs, as they do built in PoE and allow
> centralized configuration. The downside is the cost. While I don't
> expect this project to be done for free, $2600 for the switch and 300+
> each per MAP (estimating roughly 8 MAPS needed)

140,000 is only about 380 foot on a side. So you need a range of about half
that. Humm. Eight units sounds like a lot but I'm no expert. All that
racking might cause a lot of problems. Might be worth experimenting with a
consumer grade wireless access points and a decent aerial. Borrow one and
stick it in the middle as high as possible and see what the signal strength
is really like in practice. Does it have to be 802.11b? I think g has better
range but maybe mistaken.

(E-Mail Removed) wrote:

> Hi all, I'm looking for some good recommendations on setting up an
> 802.11b wlan to coover a warehouse that is roughly 120,000 sq ft in
> size. The ceilings are roughly 30ft high and the warehouse is filled
> with floor to ceilng racks holding boxed and palletized product. The
> purpose of this WLAN is to allow the use of handheld 802.11b scanning
> equipment to scan incoming and outgoing shipments into the warehouse
> management app. We are currently using wired scanners, which are
> located in one area at one end of the warehouse. This makes doing a
> full inventory or rescanning pallets very difficult.
>
> Currently I have looked at the 3com MAP's and Wlan switch. These units
> seem to cover all of our needs, as they do built in PoE and allow
> centralized configuration. The downside is the cost. While I don't
> expect this project to be done for free, $2600 for the switch and 300+
> each per MAP (estimating roughly 8 MAPS needed) might be a hard sell to
> the powers that be.
>
> I've also noticed that D-link makes MAPS and Wlan Switches that also do
> PoE. But I'm weary about going with Dlink for something that needs high
> availability.
>
> I am aware that I could also go with several standard AP's and
> configure them with the same SSID's and Key's and the devices could
> just roam between them. I have done this in the past in situations
> where mutlipe AP's were needed for coverage reasons and I had no
> significant problems. The downside to this is the individual
> configuration and lack of integrated PoE for most devices of this
> nature. The upside is, naturally, the cost.
>
> Can anyone make some good suggestions on either products or
> methodologies to cover what I'm trying to do here? I already have some
> good ideas that would accomplish the goal. I"m just looking for
> suggestions or ideas from those who may have already ventured down this
> road and might have more direct experience.
>
> Thanks!
>

It depends on how well the 2.4GHz signals penetrate the palletized/boxed
product. With good signal penetration, a few stationary WAPs might be
able to cover all the aisles. With poor penetration (which is rather
likely), you may want to consider a whole different strategy of buying
portable (handheld) inventory recorders instead of an online system.
--
Cheers, Bob

(E-Mail Removed) hath wroth:

>Hi all, I'm looking for some good recommendations on setting up an
>802.11b wlan to coover a warehouse that is roughly 120,000 sq ft in
>size. The ceilings are roughly 30ft high and the warehouse is filled
>with floor to ceilng racks holding boxed and palletized product.

This is also known as the ultimate maximum reflection environment.
I've helped setup wireless in a similar (cold storage) environment.
Conventional wisdom is to "illuminate" the aisles. We used Cisco 340
802.11b access points, which are rather crude by todays standards.

The big problem turned out to be mutual interference between access
points. We initially installed them high, near the roof, in order to
cover the greatest area. All they did was interfere with each other.
When they were moved to about 10 ft off the floor, we lost coverage,
but the interference was less.

We also had a big problem with seamless roaming. The protocols simply
don't exist to do it right. Each company has a proprietary solution.
The inability to move automatically to the "best" access point was a
serious problem covering lunatics that would ride the forklifts down
the aisles taking inventory with a wireless bar code gun. It also
interfered with the bar code gun "laser tag" games. Since the
seamless roaming requires cooperation in the client radio, using a
mixed mess of clients was not a great idea (which we did anyway).

>The
>purpose of this WLAN is to allow the use of handheld 802.11b scanning
>equipment to scan incoming and outgoing shipments into the warehouse
>management app.

Good. The scanners are not moving. That avoids the roaming problem.

>We are currently using wired scanners, which are
>located in one area at one end of the warehouse. This makes doing a
>full inventory or rescanning pallets very difficult.

Again, if you are moving, you're not going far. One company ended up
with a computer on a roll around cart. It had an 802.11b wireless
connected computer and wired bar code reader attached. The cart was
always buried in paper. Not as fast as riding the fork lift, but more
reliable.

Don't use repeaters. They only cause interference.

Check that your software doesn't require a 100% reliable connection.
The stuff I was working with would hang if even one packet was lost.

Verify data reception. The operators would pull the trigger to scan
and nothing would happen. So, thinking they missed the bar coded
target, they would do it again and again and again. When they moved
back into range of the radios, the reader would empty its buffer and
record the same entry as many times as they pressed the trigger.

Spend some effort getting proper antennas. Most wireless switch
vendors do not provide external antennas and have an omni pattern.
That's usually fine, but not for illuminating a narrow aisle. You
need a directional antenna, that will concentrate *ALL* the RF down
the aisle and nowhere else. 8dBi to 14dBi panels seem to work with
6ft aisles. IMHO, the antenna is the most important part of the
puzzle.

I cringe every time someone mumbles "self-configuring" and
"self-optimizing". That's a guaranteed service call for "nobody
changed anything but nothing works" type of call.

>Currently I have looked at the 3com MAP's and Wlan switch. These units
>seem to cover all of our needs, as they do built in PoE and allow
>centralized configuration. The downside is the cost. While I don't
>expect this project to be done for free, $2600 for the switch and 300+
>each per MAP (estimating roughly 8 MAPS needed) might be a hard sell to
>the powers that be.

All the wireless switches are expensive because they're all
proprietary. I think a wireless switch with PoE is the way to go. It
solves the number one time burner problem, central system management.
It's something nobody thinks about until the problems start. You
either pay for centralized systems management at the front end, or
burn the IT labor fixing the mess later.

Look into other wireless switch vendors offerings:
Symbol
Aruba
Cisco
Entrasys
Xirrus
Foundry Networks
(probably more vendors)
I haven't been keeping up to date on Wireless Switches so can't advise
on specific products. There was quite a bit of new goodies product
released at Interop last week.

I dunno about this one:
http://www.dlink.com/products/?sec=2&pid=434
http://www.dlink.com/products/?pid=435&sec=0
At $2500, it looks much cheaper than the others. No experience with
it. I don't like the looks of the circular access points. 802.11a/b/g
is nice. No obvious external antenna connection. "Zero-Config
Installation"??? I'm worried.

>I've also noticed that D-link makes MAPS and Wlan Switches that also do
>PoE. But I'm weary about going with Dlink for something that needs high
>availability.

I've had problems with DLink products in the past. In general, if it
doesn't work out of the box, it's not going to get fixed. That's the
real problem. All the vendors have their problems, but only a few
bother to fix them.

>I am aware that I could also go with several standard AP's and
>configure them with the same SSID's and Key's and the devices could
>just roam between them. I have done this in the past in situations
>where mutlipe AP's were needed for coverage reasons and I had no
>significant problems. The downside to this is the individual
>configuration and lack of integrated PoE for most devices of this
>nature. The upside is, naturally, the cost.

Yep, that's about it. All your eggs in one vendors basket, or a
management nightmare. There's no in between. Toss a coin (or toss
your bank book) to decide.

>Can anyone make some good suggestions on either products or
>methodologies to cover what I'm trying to do here? I already have some
>good ideas that would accomplish the goal. I"m just looking for
>suggestions or ideas from those who may have already ventured down this
>road and might have more direct experience.

Well, I've only helped on 2 warehouses. My bag is RF and antennas.
Layout, location, and antennas are serious problems in a highly
reflective environment. My contribution was mostly to move the radios
down and add proper antennas. I also reduced the number of access
points in the building from about 14 to 8 to reduce mutual
interference. Beyond that, the applications people fixed their
program so that it could tolerate connection outages. We never did
fix the roaming problem. Also, I supplied the giant stickers with the
front and back side bar codes for the laser tag games.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Have you considered using an AP with a distributed antenna? Run the antenna
along the ceiling in a manner that best illuminates the aisles. I've never
heard of distrubuted antennas being used for WiFi, but it shouldn't be a big
deal to make one if they're not commercially available at this frequency.
It's basically a leaky coax like the distributed antennas used in tunnels to
serve vehicles passing through.

George


<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> Hi all, I'm looking for some good recommendations on setting up an
> 802.11b wlan to coover a warehouse that is roughly 120,000 sq ft in
> size. The ceilings are roughly 30ft high and the warehouse is filled
> with floor to ceilng racks holding boxed and palletized product. The
> purpose of this WLAN is to allow the use of handheld 802.11b scanning
> equipment to scan incoming and outgoing shipments into the warehouse
> management app. We are currently using wired scanners, which are
> located in one area at one end of the warehouse. This makes doing a
> full inventory or rescanning pallets very difficult.
>
> Currently I have looked at the 3com MAP's and Wlan switch. These units
> seem to cover all of our needs, as they do built in PoE and allow
> centralized configuration. The downside is the cost. While I don't
> expect this project to be done for free, $2600 for the switch and 300+
> each per MAP (estimating roughly 8 MAPS needed) might be a hard sell to
> the powers that be.
>
> I've also noticed that D-link makes MAPS and Wlan Switches that also do
> PoE. But I'm weary about going with Dlink for something that needs high
> availability.
>
> I am aware that I could also go with several standard AP's and
> configure them with the same SSID's and Key's and the devices could
> just roam between them. I have done this in the past in situations
> where mutlipe AP's were needed for coverage reasons and I had no
> significant problems. The downside to this is the individual
> configuration and lack of integrated PoE for most devices of this
> nature. The upside is, naturally, the cost.
>
> Can anyone make some good suggestions on either products or
> methodologies to cover what I'm trying to do here? I already have some
> good ideas that would accomplish the goal. I"m just looking for
> suggestions or ideas from those who may have already ventured down this
> road and might have more direct experience.
>
> Thanks!
>

On Fri, 19 May 2006 03:12:34 GMT, "George" <(E-Mail Removed)>
wrote:

>Have you considered using an AP with a distributed antenna? Run the antenna
>along the ceiling in a manner that best illuminates the aisles. I've never
>heard of distrubuted antennas being used for WiFi, but it shouldn't be a big
>deal to make one if they're not commercially available at this frequency.
>It's basically a leaky coax like the distributed antennas used in tunnels to
>serve vehicles passing through.

I've used power splitters and they do work in very specific
applications. You run a power divider to the access point and connect
one antenna on each port. I had one system running a 4 port power
divider. One directional antenna on each aisle should illuminate the
required area.

However, there's are problems. The power divider reduces the signal
by half for each 2 ports (plus about 0.5dB loss per port). A 4 port
power divider has about -6.5dB loss per port in transmit, and about
0.5dB loss in receive. That's less than half the range. With a
reasonable amount of TX power to compensate for the loss, it should
work.

Another catch is that the antennas have to be arranged so that they
don't see each other. That's easy enough to do on a radio tower. Just
point the antennas in different directions. However, in a closed
warehouse, the isolation is going to be minimal and the reflections
are going to be horrible. There will be nulls and inter-symbol
interference, both of which are fatal. It can be made to work with
careful antenna selection and positioning, but I'm not optimistic. The
one indoor system where I used a power splitter had to revert to
individual AP's, on different channels, in order to get things to work
well.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

Generally, trying to cover the same area using multiple antennas off a
splitter will not work reliably because of position-dependent phase
cancellation as you mentioned. In fact, one technique commonly used to
build antenna arrays with shaped patterns is to drive multiple antenna
elements off a splitter. Their patterns are due to controlled signal
cancellation.


"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Fri, 19 May 2006 03:12:34 GMT, "George" <(E-Mail Removed)>
> wrote:
>
>>Have you considered using an AP with a distributed antenna? Run the
>>antenna
>>along the ceiling in a manner that best illuminates the aisles. I've
>>never
>>heard of distrubuted antennas being used for WiFi, but it shouldn't be a
>>big
>>deal to make one if they're not commercially available at this frequency.
>>It's basically a leaky coax like the distributed antennas used in tunnels
>>to
>>serve vehicles passing through.
>
> I've used power splitters and they do work in very specific
> applications. You run a power divider to the access point and connect
> one antenna on each port. I had one system running a 4 port power
> divider. One directional antenna on each aisle should illuminate the
> required area.
>
> However, there's are problems. The power divider reduces the signal
> by half for each 2 ports (plus about 0.5dB loss per port). A 4 port
> power divider has about -6.5dB loss per port in transmit, and about
> 0.5dB loss in receive. That's less than half the range. With a
> reasonable amount of TX power to compensate for the loss, it should
> work.
>
> Another catch is that the antennas have to be arranged so that they
> don't see each other. That's easy enough to do on a radio tower. Just
> point the antennas in different directions. However, in a closed
> warehouse, the isolation is going to be minimal and the reflections
> are going to be horrible. There will be nulls and inter-symbol
> interference, both of which are fatal. It can be made to work with
> careful antenna selection and positioning, but I'm not optimistic. The
> one indoor system where I used a power splitter had to revert to
> individual AP's, on different channels, in order to get things to work
> well.
>
>
> --
> # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
> # 831-336-2558 (E-Mail Removed)
> # http://802.11junk.com (E-Mail Removed)
> # http://www.LearnByDestroying.com AE6KS

On Fri, 19 May 2006, in the Usenet newsgroup alt.internet.wireless, in article
<(E-Mail Removed)>, Jeff Liebermann wrote:

>George" <(E-Mail Removed)> wrote:

>> Have you considered using an AP with a distributed antenna?

>> It's basically a leaky coax like the distributed antennas used in tunnels to
>> serve vehicles passing through.

>I've used power splitters and they do work in very specific
>applications.

I think he's referring to Andrews Radiax or Cablewave Radiaflex.

140K sq ft - that's 374 foot square, or 350 x 400, and so on. I would think
the coupling loss would be a bit to high, but _otherwise_ this might be
worth have a manufacturer's application engineer talk about it. It's not
something you want to 'buy and try' - the other way round might be better,
but I don't know how many manufacturer's reps would take the gamble.

>However, in a closed warehouse, the isolation is going to be minimal and
>the reflections are going to be horrible. There will be nulls and
>inter-symbol interference, both of which are fatal.

Yeah, that's more of my concern.

Old guy

(E-Mail Removed) (Moe Trin) hath wroth:

>On Fri, 19 May 2006, in the Usenet newsgroup alt.internet.wireless, in article
><(E-Mail Removed)>, Jeff Liebermann wrote:
>
>>George" <(E-Mail Removed)> wrote:
>
>>> Have you considered using an AP with a distributed antenna?
>
>>> It's basically a leaky coax like the distributed antennas used in tunnels to
>>> serve vehicles passing through.
>
>>I've used power splitters and they do work in very specific
>>applications.
>
>I think he's referring to Andrews Radiax or Cablewave Radiaflex.

OK. I can do that. I don't think it will work. Let's grind the
numbers.

>140K sq ft - that's 374 foot square, or 350 x 400, and so on. I would think
>the coupling loss would be a bit to high, but _otherwise_ this might be
>worth have a manufacturer's application engineer talk about it. It's not
>something you want to 'buy and try' - the other way round might be better,
>but I don't know how many manufacturer's reps would take the gamble.

It will be a long time before I find a manufacturers rep that can do
calculations much beyond the lunch bills and expense reports.

PREDICTION OF INDOOR WIRELESS COVERAGE BY LEAKY
COAXIAL CABLE USING RAY TRACING
http://www.bell-labs.com/org/wireles...b/vt98_spm.pdf
Ugh. Lunch bills and expense reports are easier. Never mind.

So, let's do this one with Andrew Radiax. The smaller and cheaper RCT
"radiating mode" coax isn't rated at 2.4Ghz. You have to go to 1 1/4"
coax before it can be used. So much for RCT coax.
http://www.antennasystems.com/Radiax.html
http://www.andrew.com/search/BN_661.aspx

1/2" RLX RXP4-1 coupled mode should work better:
http://www.andrew.com/search/BN_RXP4-1.aspx
http://www.andrew.com/search/BN_10592.aspx
$4.10/ft from Tessco or $6,500 for just the 1600ft of coax. Seems a
bit overpriced, but that's what the distributor wants.
Are you *sure* you wanna use leaky coax?

Example of how to calculate a cellular link budget with Radiax.
http://www.andrew.com/search/BN_671.aspx

Basic specs at 2.4Ghz for RLXP4-1 is 6.7dB/100ft and -62dB coupling
loss at 6.5ft. Let's do 2 access points with a 2 way power divider at
midpoint using 4ea 400ft coax segments. Diving in:

TX power: +20 dBm (assuming a 100mw radio)
Coax feed loss: -3 dB (including connectors)
Power divider: -3.5dB
Cable loss: -26.8dB (400ft at 6.7dB/100ft)
Coupling loss: -62 dB (at 6.5ft)
=======
Signal level: -75.3dBm at 6.5ft.

Perverse square law says that power drops -6dB every time we double
the distance. This thing has to work half way across the building
which is 400ft across. At 200ft the range is:
200 / 6.5 = 30.8 times as far [1]
20 log (30.8) = -30dB

So, the signal level in the middle of the warehouse is about -105 dBm.
That isn't even close to functional. The average 802.11g laptop, at
11Mbits/sec connect speed, requires at least -65dBm to function. Add
about 15-20dB for a decent fade margin. This leaky coax model is at
least 55dB short of being functional. That's a HUGE amount.

What went wrong? The large coax loss through 400ft of Radiax
certainly didn't help. It would probably barely work in close
proximity to the Radiax, perhaps to 10ft, but not much more.

Why does it work inside buildings and tunnels? Very few try leaky
coax at 2.4GHz for extended distances. Most systems are at cellular
800/1900MHz frequencies. In the offices, they go in suspended
ceilings, which are fairly close to the users. In tunnels, the coax
is on the wall of the tunnel, which is also fairly close to the train.
In buildings, the coax is run above the hallways, again close to the
users.

One could do the same with the warehouse except that the ceiling is
20ft high, not the usual 8ft suspended ceiling. That's not as bad as
200ft away across the warehouse floor, but still far enough to reduce
the signal level to unusable.

Incidentally, I've re-discovered that mounting Radiax against a
concrete wall is a bad idea. It's really a long antenna and doesn't
like objects in the near field. We had to use spacers to keep the
coax away from the walls and pipes. Also, sharp bends tend to tear
apart the coax at the slots.

>>However, in a closed warehouse, the isolation is going to be minimal and
>>the reflections are going to be horrible. There will be nulls and
>>inter-symbol interference, both of which are fatal.
>
>Yeah, that's more of my concern.

The warehouses that I cleaned up had this problem. That's where I
found that 802.11g is far more tolerant to dealing with reflections,
multipath, deep fades, nulls, and other cancellation/reinforcement
phenomenon. When I fixed the wireless connect speed at the access
points to 12Mbits/sec, the fade/null problems were greatly reduced.
However, the ultimate solution was to position and specify the
antennas so that they did NOT see each other, thus preventing these
effects.


[1] I have this handy table on my wall mostly for inverse square law
guesses. Double the distance and lose 6dB:
dB = 20 log (multiplier)

Distance Power Loss
Multiplier dB
0 0
2 -6
4 -12
8 -18
16 -24
32 -30
64 -36
128 -42
256 -48
512 -54

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news(E-Mail Removed)...
> (E-Mail Removed) (Moe Trin) hath wroth:
> Incidentally, I've re-discovered that mounting Radiax against a
> concrete wall is a bad idea. It's really a long antenna and doesn't
> like objects in the near field. We had to use spacers to keep the
> coax away from the walls and pipes.

Possibly rebar in the concrete as well.