AP1250 AG with multiple antennas.

Unanswered Question
Oct 17th, 2007

Have preordered some 1250AG radios and are preparing to install some outdoor omni hotspotantennas with cables. Will there be enough with 2 antennas on each band if we only use one channel (not bonding)? Will 3 antennas give any advantage using only one channel?

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Overall Rating: 3.5 (2 ratings)
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srahn Thu, 10/18/2007 - 04:41

Yes, the three antennas utilizing the MIMO feature will provide greater throughput and performance than using just two antennas. Of course, the real question is whether or not you need the added performance for the application this solution will be supporting. Here's a link to the nice blog on MIMO...


http://blogs.cisco.com/wireless/2007/09/whats_up_with_mimo.html


sorvarit Fri, 10/19/2007 - 07:38

Ok. Maybe we install cables and antennas x3 then on each band! Read something about 802.11n outdoor use and that the standard wouldnt give much performance in free space, but that article was over an year old so maybe the situation is different now?

http://80211n.wifinetnews.com/archives/2006/02/outdoor_n_speed.html

Any comments? Just a waste of money to shoot longhaul links with 802.11n?

dennischolmes Sun, 10/21/2007 - 09:34

Over the last couple of years I have followed closely the draft 802.11n standard and as a member of the IEEE Standards Association personally, I can tell you this has been one of the hardest debated standards in the history of the IEEE. There is a lot of money riding on this standard and who wins certain pieces of it. 802.11n unlike most other standards isn't really one standard but several. There are a certain number of minimum benchmarks that must be met by the standard but there are also several optional features that can be supported and still considered 802.11n. To fully understand 802.11n one must understand the history of 802.11 and the earlier standards shortcomings such as multipath distortion and contention rules. One must understand multipath channel distortion and how the 802.11 standard uses multipath to its advantage as well as how the new standard enforces new rules at the mac layer to fully see the benefit of moving to this standard. The standard would not greatly help in free space, but as we live in the real world, free space is not a real issue. In almost any environment we encounter surfaces that create some level of multipath distortion. The presence of this distortion is one way 802.11n increases performance. I have included a white paper for your review. This paper explains the standard and how the increased performances are achieved. Happy reading.



sorvarit Mon, 10/29/2007 - 07:28

Thanks for your helpfull reply Dennis!

Will do some labtest for outdoor performance when our 1250s arrive. The terrain in our area are varied with many small hills, mountains and valleys so we would probalby have some levels of multipath distortion.

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