1250 AP Planning Indoor and Outdoor

Unanswered Question

Greetings,

I am planning a new install with 1250 APs. This structure is steel so I have to plan for both indoor and outdoor AP deployments. Indoors, I am planning to use the 5gHz radios in order to allow for more channels, Outdoor I am lookng for advice on which frequency to use. Any one have an opinion?

Follow-on questions are:

-If the outdoor AP needs to be installed in a location about 40 feet from an omni antenna, what is the range and throughout I can expect for the 1250 with a 8db antenna? A 6db antenna? Assume cabling is LMR400.

-Will the 1250 allow for use of just a single remote omni antenna? If it could only have a single coax connection to the 1250, what would the effect be on the range and throughput?

TIA

Charlie

I have this problem too.
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larrywoods Thu, 09/20/2007 - 10:32

Do a scan and see the least congested frequency. Other than that, on 802.11A, you have plenty to chose from and chances are you do not really have to worry about a lot of interference sources.

You can expect pretty good range if this is outdoors and the area is open. I have seen distances upward to 300-400 feet but there was nothing in the way. If there are a lot of steel structures and buildings, you will probably not see these types of ranges.

If you use a single omni antenna on the 1250 (the new 802.11N radio not yet available), you wouldnt want to use one antenna because you would then nullify the ability to use 802.11N. I believe that these can work with one antenna but do not expect it to be 802.11N (pre-N, draft 2.0) compatible.

rpettersen Fri, 09/21/2007 - 00:07

I also plan to use the new 1250 between two buliding's and I also are interested in how many antenna's I need.

Today I have a 1230 with one 18dBi antenna, I hope to use two antenna (one for receiving and one for transmitting). 802.11n use three antenna....

Could we have a reply from Cisco regarding this issue. I need to continue with planning for 1250 access points in outdoor sittuations where we would like to have 802.11n capability.

This thread has brought up some good questions that I have not seen answered elsewhere:

-Will the 1250 be able to deliver 802.11n outdoors (with a lack of multipath)?

-What antenna configurations will support this?

-If cisco does not have an antenna that can be used in this way, can they reccommend another antenna for both 2.4 and 5 gHz operation outdoors?

Thanks

dennischolmes Wed, 11/14/2007 - 14:40

Your question about 802.11n is a very valid one. Yes, multipath is less outdoors, but it still exists. So you will get some benefit from the MiMo on the unit. You will also see a significant improvement based on better packet aggregation. If you enable 40mHz spectrum utilization, remember you will only have one channel available in the 2.4 ghz spectrum. Using this AP with one antenna is not something I would do. Using all three allows for better MiMo and beamforming. See the attached document. Bear in mind that packet aggregation increases throughput by queing larger packets for sending thus reducing overhead. This is good for data, but not necessarily so for voice traffic.

Attachment: 

Thanks for the reply and for th ehlpful advice on multipath and the general performance improvements with 802.11n

Im aware that 40mHz will only allow one channel in the 2.4 range and more in the 5.0 range. Therefore I am expecting that there will be more use of the 5 gHz range in this space which will have potentially a lot of overlapping zones.

Im not keen to use the AP with just one antenna, but I want to use it outdoors and I have not come across an outdoor omnidirectional antenna with a form factor that I can work with, let alone one that has 3 pigtails to connect to the respective connectors on the AP. Id like something in a small patch that I can put on a vertical surface (wall) to offer good 802.11n 5 GHz coverage to an outdoor area about 40 feet square. Any ideas?

Appreciate your note on voice, but Im not sure I understand why voice is not happy over this kind of network. Is this a well know problem with 802.11n? How will this affect growing voip implementations, let alone dual-mode phones (GPRS/EDGE & WIFI for example)?

dennischolmes Wed, 11/14/2007 - 16:48

I am currently working on a 3 element directional patch antenna with a 3rd party manufacturer. I'll let you know how that comes along. As for voice, the problem is potentially in the queing algorithms. The 11n standard holds the packet until the larger packet is "filled up" for a lack of better words. Since voice samples are sent in smaller packets you must now account for the additional latency caused by this.

Thanks again for the reply Dennis.

Would of course like to asask when this might be available, but the more immediate question is what kind of cable and connectors should be specified for an install using such an antenna. Also, it is outdoor-capable?

Understand the added latency might be an issue for voice. Is this a deal-breaker for 802.11n for voice? Would the 1250 allow 802.11n in the 5 GHz range for delivering multimedia stuff as well as permit 802.11b/g for voip applications and traditional (avoiding the latency for voice packets) ?

Endless questions...

dennischolmes Mon, 01/28/2008 - 13:49

There are currently no really good outdoor antennae. I would check with Tessco to see what they have gotten tested so far.

rpettersen Thu, 01/31/2008 - 02:30

Hi !

I have set up a pair of 1250 in a outdoor

setup using 4 D-link ANT24-2100. The distance between the two buildings are around 750 meter.

I have no problem geting "m7" as the wireless speed which is th higest speed you get with only two antenna's.

In the beginning the choise of frequincy was wrong, but adjusting the frequency have solved all my problems.

I gues next time I will choose 802.11a radio

and antenna's due to more frequency channels availible.

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