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AIR-1242AG AP's for Hotel Wireless Solution

Folks - just coming in on the tail end of a project where a wireless solution is in the process of being implemented. Quick question for anyone who may be able to assess.

Quick overview - a 4 floor hotel where from the mid-point of each floor, the distance is appx 150' to the end of the hallway, in each direction.

2 1242 AP's have been installed in utility rooms, with 1 on the 4th floor, and the other on the 2nd floor. Each AP has qty-2 AIR-ANT2485P-R antenna's attached via low-loss cable (Cisco cable provided as part of the solution). The 4th floor has one antenna mounted midway down the right wing, and the other antenna mounted midway down the left wing. 2nd floor has the same antenna location configuration.

Has anyone worked on a similar project as this, and does this sound like the correct number of antenna's to accomodate good coverage on each floor? The reason I ask is when you walk the hallway from end to end, checking with a laptop, you get good signal strength. However when you start ducking into the hotel rooms, the only rooms that maintain good signal quality are the rooms directly adjancent to where the antennas are located. I would say 2 rooms each direction from the antenna location, are acceptable. As soon as you start getting 3 or 4 rooms away from the antenna, signal strength in the rooms gets quite diminished. Guests are also complaining of low signal strength. I am no expert on this by any stretch, and have not worked on a project such as this before. But it's looking like 3 antenna's per wing (6 total per floor) might be more what's needed.. which sounds excessive to me.

A rather winded blurb to see if anyone has worked on a similar project. The customer was not sold any SmartNet on this new install, (which is about 2 weeks old) so trying to figure that out before calling TAC. All the 1242's are set to their default parameter settings for the most part (antenna specific settings, etc)i.e, the "Optimize radio network for" is set to "range" for each AP. Not sure if I need to be setting add'l parameters for optimum settings.

Anyways, much obliged for anyone's assistance.

6 REPLIES
Green

Re: AIR-1242AG AP's for Hotel Wireless Solution

Is the hallway one long stretch (the far end of one wing can see the far edge of the other wing)?

Using the antennas that far apart from one AP (typical would be ~3 feet max) will pretty much guarantee bad performance.

The dual antennas are there for diversity .... to help reduce the effects of multipath and RF "nulls" ... not to increase the coverage distance ... only one antenna is active at a time.

Was a site survey done (before the design)?

On the little information you've provided, I'd guess that you need at least three APs per wing ... maybe more.

Some kind of custom setup might work using something like Radiax (www.andrew.com)and some amplifiers. By custom, I mean, designed, installed, and compliance tested (as in, Federal compliance certification).

All-in-all, I think you're hosed. I can't see making this solution work without a lot more equipment.

A lightweight AP system might work better for you, if you have the cabling in-place.

Also, when you set the system for "range," I believe it keeps the data rate down (lower data rates perform better for distance).

TAC will probably not be able to help you, beyond telling you that on the surface, this looks like a really bad design.

Good Luck

Scott

New Member

Re: AIR-1242AG AP's for Hotel Wireless Solution

yikes! not what I was wanting to hear :)

Yes, the hallway's are one long straight visible stretch, from one end to the other.

The previous gentleman I do know worked with Cisco pre-sales sppt, had some test equipment shipped onsite which was setup. The extent of testing done with the loaner equipment, I do not know. Not sure I understand the ~3ft max antenna location comment, as part of the solution included 100ft low-loss coaxial cables, along with some 20ft cables. This "design" approach had to be done with the understanding that the antennas would be located at a distance away from the AP's, up to the max length of the cable. I would have to think that this design preview was conferred on with Cisco, but I can't say for sure on this. But that's an interesting comment nonetheless.

Only 1 antenna operates at a time? As noted in my earlier comment, good signal strength when you walk from one end of the hallway to the opposite end. It's just when you move into the room that things go dismal. But then again, that's the whole objective. Hallway signal goes to crap when you get in immediate proximity of the elevator. So an AP in this area, would be a given as well I believe.

I'm not sure if any comprehensive site survey was done. My guess is no, at least nothing more than walking the hallway with a laptop, seeing where their original wireless equipment was failing, in regards to signal strength.

Cabling for the antenna is in place, run thru the ceiling's etc. I'll take into consideration your lightweight AP suggestion.

TAC is ultimately where I need to wind up, but posting here for "been there - done it" suggestions/support. Appreciate your time in responding - Have a good evening -

Green

Re: AIR-1242AG AP's for Hotel Wireless Solution

Here's a link that explains the diversity aspect of using two antennas:

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008019f646.shtml

Usually the two antennas are located ~5 inches to 3 feet apart. They are not designed to be much more than that (like a site-to-site relay or coverage expansion).

It's OK to have them away from the AP, but both antennas shold be covering the same area.

Also note that the cabling (as described) is eating ~ half your signal (4.4db/100feet, actually ~60% or so).

3db represents a 50% loss (or 2x gain) .... here's a link that explains LL cabling:

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00801c12c2.shtml

What kind of antennas are you using?

It is not likely that Cisco (or, at least someone from Cisco that knows wireless) ever saw this config ... it's well-beyond Cisco's implementation recommendations.

Be prepared to send a scale diagram when you talk to TAC.

IMHO, there is no way you'll get this system working as desired without a significant addtional investment.

Good Luck

Scott

New Member

Re: AIR-1242AG AP's for Hotel Wireless Solution

Scott - the antenna's mounted in each hallway are the AIR-ANT2485P-R models. One mounted mid-way down each wing of each floor (4th and 2nd). Premise being the antenna on the 4th will manage the 4th floor rooms, and radiate down to cover the 3rd floor rooms. That's what I was told.

2 quick questions. Can you offer what you "think" would be the additional equipment required to get this working to an acceptable level, or where you would start? You think 3 1242 AP's per floor? Each initially mounted splitting the floor into equal 1/3rd distances?

Second, can you suggest where to turn for experienced consulting assistance with this commercial grade type project?

Again, appreciate the assistance -

Hal

Green

Re: AIR-1242AG AP's for Hotel Wireless Solution

The antennas chosen are "patch" antennas - they're somewhat directional (in this case, the beamwidth is ~56 degrees, with an elevation spread of 66 degrees) ... you probably would want an "omni" which radiates 360 degrees.

Here 's a link to the specs of the antenna you're using:

http://www.cisco.com/en/US/products/hw/wireless/ps469/prod_installation_guide09186a008068f2b1.html

The "E-Plane" (blue) chart shows the azimuth pattern, as seen from above; "0" on the chart would be the direction the face of the antenna is pointing. The "H" plane represents the shape of the radio beam as seen from the side, because it's directional, "0" represents a line eminating from the center of the radiator in the primary direction.

Compare it with this antenna, AIR-ANT5145V-R:

http://www.cisco.com/en/US/products/hw/wireless/ps469/prod_installation_guide09186a0080338872.html

Notice that the horizontal pattern (blue) is radiating (more or less) equally ... something you'd need to cover the larger area. The Vertical pattern (red) has (more or less) enlongated symmetrical lobes ... by experimenting with the orientation, this would (probabl) do a much better job covering the room areas.

The antenna you're currently using is shooting the bulk of it's signal into the floor.

If you have the overhead space, a "stick" hanging down from the ceiling like this one AIR-ANT1728 :

http://www.cisco.com/en/US/products/hw/wireless/ps469/prod_installation_guide09186a0080286064.html

Would give you a wider coverage, and a tighter pattern to the horizon (this would be best, but may have practical or cosmetic issues)

It would be nearly impossible to provide specifications for your setup without a good site survey. The issue that complicates it the most is type of construction of the walls & doors, which goes towards the level of signal penetration.

Changing the antennas should get you roughly 50% more coverage, maybe more. I would further guess that you'd need at least two, probably three (maybe more) APs per wing.

The complication there is getting the setting for the channels (there are only three non-overlapping channels - 1, 6, and 11 - on 802.11g frequencies) .. you'd need to stagger the channels and possibly reduce power to keep the AP on channel 1 of the East wing from interfering with the AP using channel 1 in the West wing.

You will probably need APs on each floor where you'd like coverage.

It can easily get "complicated" ... that's the value of a good site survey "up-front."

I can't offer any suggestions for a designer/implementer ... but if you scan some of the posts on the wireless forum, you'll find a number of posters from various organizations that may be able to work with you. Look for posts that are rated, especially with red check marks (indicating that one or more of the replies solved the problem).

Or, you can click on the links of the "Meet the NetPros" listed (left-most column) and check the profiles to see what organizations they are associated with.

Keep posting if you have an other questions.

Good Luck

Scott

New Member

Re: AIR-1242AG AP's for Hotel Wireless Solution

Most grateful for your time and assistance in responding Scott. I think at this time myself and others within the company will regroup and strategize on how to move next.

I'm thinking engaging TAC in a more diligent manner and perhaps another round of test equipment may be the way to proceed, with the initial focus on getting a single floor within the building working at an acceptable level. One floor at a time.

Again, much obliged for the volume of information you've provided. Have a good one -

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