Wireless: 2x3 vs 3x3, MIMO, etc

[MrEgo]

We're looking at upgrading our wireless infrastructure. We need to replace our access points across 7 different buildings, and each building is fairly large (2 stories, about 400m x 200m).

We're starting to take bids on the hardware that will be used for the access points. A few of the vendors said they offer 3x3, while Cisco says they only offer 2x3, but they claim that their 2x3 is just as good if not better than the others' 3x3.

I know that 3x3 means 3 transmitting antennas and 3 receiving antennas, but I don't know how to relate that to real-world performance. How much better is 3x3 vs 2x3? Generally, higher numbers are better, but that's not always the case. Cisco claims that 3x3 is unncessary, but we can't understand why that is.

Does anyone have a fairly simple way to describe the benefits/shortcomings of 3x3 and 2x3?

Also, is MIMO a term that means you have multiple transmissions frequencies and multiple receiving frequencies?

 

[theevilsharpie]

Also, is MIMO a term that means you have multiple transmissions frequencies and multiple receiving frequencies?

No, it describes the process of using multiple antennas to transmit and/or receive a signal.

As for your dilemma, Cisco will claim whatever they feel they need to claim to get a sale, even if said claim is bogus. If they say they can achieve identical performance as competing products with fewer antennas, make them prove it.

 

[MrEgo]

Do you happen to know why they might make a claim like that? I guess is there any logical reason that a 2x3 would perform the same as or outperform a 3x3?

 

[Gamingphreek]

No, it describes the process of using multiple antennas to transmit and/or receive a signal.

As for your dilemma, Cisco will claim whatever they feel they need to claim to get a sale, even if said claim is bogus. If they say they can achieve identical performance as competing products with fewer antennas, make them prove it.

Actually you are both correct.

MIMO does have multiple transmission frequencies and multiple receive frequencies. The same data is sent over each frequency. Then when the data stream reaches the destination, the router (or whatever receives this signal) performs a checksum on each and uses whatever one it determines has the correct data.

The real strength of MIMO is not increased bandwidth per se, it is that it preserves data integrity thereby limiting retransmits which would ordinarily slow a reliable connection.

As for 2x3 vs 3x3, just look at what I said earlier. If it happens that you have virtually no packet loss or interference on your network, then it should perform the same if the exact same antennas and hardware are used. Using a 2x3, unless I am mistaken, is a waste as 1 antenna will be virtually useless.

Despite that, if you have a lot of packet loss and interference on your network (ie: Going through multiple sets of walls) it is highly likely that one particular frequency may yield a correct data stream thus limiting the number of retransmits. In this case 3x3 would perform better.

If I had to guess, Cisco is places a LOT of value on the hardware/software on their routers and also are making the 2x3 > 3x3 claim in certain cases only.

-Kevin