Note: Interference between cards in a case can be a problem, but.... With MIMO self interference between polarity connectors is less of a problem than with trying to use two seperate radios not MIMO.
Let me tell you why I feel this. In theory OFDM for Full modulations needs at minimum 25db isolation between ports. I've seen huge difference in performance using antennas that had 35-40 db isolation between ports compared to 25db. Because of this, when fiorst testing Ubiquiti MIMO I was very concerned about this. I was concerned that a Nano MIMO only had about 16db of isolations between antenna polarities, 19db sector only about 22db isolation, and large sector about 28db isolation between feeds. So, I'd asume the 28db antenna would way out perform the NANO, in regards to polarity isolation, considering JUST a single link. (not considering intference or isolation from other seperate radio links.Obviously the larger antenna has better front to back ratio isolation from other sectors than Nonos that have little.). Any way we recently did tests on a 8 mile Ubiquiti MIMO link, comparing results using each of the three antenna type. (rockets with ext versus Nanos). The goal was to determine whether the NANO could work adequately as a AP sector, IF there were not many APs at that site. The results were.... Absolutely no difference in performance, regardless of which antenna we used. (again, just talking about polarity isolation, using MIMO on one link, on a clear channel). The Ubiquiti MIMO worked at full capacity even though the isolation between polarities is not very high on a NANO. I was very surprised. I do not know how this will play out StarOS MIMO. >The radio system is an ALIX mini-itx and it has 5 radios, It will be very hard to trouble shoot your MIMO link based on MIMO's merit, as with so many radios within the case, it will be really hard to isolate so many cards from each other, to know whether interference is from cards or MIMO polarities. Receiver overload can also be a factor. Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: Gino Villarini To: WISPA General List Sent: Tuesday, January 11, 2011 3:37 PM Subject: Re: [WISPA] MIMO antenna cabling... Beware of interference problems between the cards in the board Gino A. Villarini [email protected] Aeronet Wireless Broadband Corp. 787.273.4143 From: [email protected] [mailto:[email protected]] On Behalf Of MDK Sent: Tuesday, January 11, 2011 4:20 PM To: WISPA General List Subject: Re: [WISPA] MIMO antenna cabling... I'm aware of cable loss issues, but in this case, that's just not an option. LMR-400 has low enough loss at 5 ghz that I don't see any big issue with using it, and the run really isn't all that long. The radio system is an ALIX mini-itx and it has 5 radios, plus a 2 radio ALIX board, all in one enclosure. BTW, it's a metal building, with the radios inside another heavy steel box, required to prevent nearby lightning strikes from shutting it down. ++++++++++++++++++++++++++++++ Neofast, Inc, Making internet easy 541-969-8200 509-386-4589 ++++++++++++++++++++++++++++++ From: support Sent: Tuesday, January 11, 2011 11:51 AM To: WISPA General List Subject: Re: [WISPA] MIMO antenna cabling... 10ft in RF cable is a Bad Idea I would put you board in a weather proof box and put it next to your antennas On 1/11/2011 1:16 PM, MDK wrote: I'm in the position of wanting to test the Star-OS MIMO mode, and it occurs to me that connecting an antenna through a few feet of cable may have some pitfalls... I'm going to use dual polarity antennas, and so I'm wondering if I need to use very closely matching cable lengths for the cables that connect the radio to the wire? The board / radio are inside the building, and the antennas will be about 10 feet away, or so. Is this an issue to be concerned about? Anyone know? ++++++++++++++++++++++++++++++Neofast, Inc, Making internet easy541-969-8200 509-386-4589++++++++++++++++++++++++++++++ --------------------------------------------------------------------------------WISPA Wants You! Join today!http://signup.wispa.org/-------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe:http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ -- Tim Steele [email protected] NITLine Support (574) 772-7550 ext 103 www.NITLine.net ------------------------------------------------------------------------------ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ ------------------------------------------------------------------------------ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
-------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
