On 13/02/2009 22:20, Jeff Liebermann wrote:

>> I have not seen any info as to how these type of units work when they
>> operate in non-n mode. In the case of a 2x2 system do they actually
>> disable one of the radios or do they reduce the throughput through both
>> radios?
>
> Nope. It switched to diversity receive mode, exactly the same as in
> an ordinary 802.11g adapter. See clues buried in the Ruckus docs at:
> <http://www.netgear.com/upload/solutions/rangemax/enUS_pdf_whitepaper_RangeMax.pdf>
> "When the SM (spatial mux) mode is not possible, a MIMO system reverts
> to diversity mode."
>
> Extra credit if you can guess which antenna is "Main" and "Aux" in
> diversity mode. Sigh...
I don't really like their explanation as all the examples quoted are
using diversity techniques, manufacturers seem to like referring to
diversity in MIMO as more antennas.
"Without doubt,the performance of MIMO systems improves with additional
diversity (i.e.,more
antennas).<http://www.atheros-xspan.com/modules/articles/files/MIMO_Pwr3_whitepaper.pdf>
In the early examples, from the netgear pdf, they have added an extra
Rx to give Rx diversity and in their 2x2 example they are using a
diversity combiner. I don't think they will have a "Main" and "Aux"
antenna system as it is possible they are using MRC and you get the
combined result.
"In contrast, switched diversity and Maximum Ratio Combining are
diversity techniques that can be implemented on just one side of a
communications link; therefore they can benefit all existing
802.11a/b/g devices."