MIMO the best thing ever?

I've just been studying wireless a lot in the last little while and I was considering how MIMO could be one of the best innovations since 802.11a.

For those that don't know, MIMO, or Multi-in, Multi-out (to paraphrase), is a transceiver method that uses multiple radios for a single line to enhance throughput and clarity of signal, being able to be fine tuned to even make reflections and phase shifting due to environmental disturbances, helpful to your wifi signal.

That being said, a lot of newer, mid to high end wireless b/g/n and a/b/g/n cards are coming out with multiple radio chains. The 802.11n standard supports up to 4x4 radio chains, but I have yet to see anything utilize that. Most commercial grade hardware has a max of 3x3 radio chains, which is to say 3 full transceivers in a single card. A good example of this would be the Intel 4965, 5300, and 6300 cards; all of which, I believe, are 3x3 radio chains for a/b/g/n wireless at 2.4ghz and 5ghz. The maximum rates differ, but that's another matter entirely.

My thought is, how useful is this? I mean that. It's beyond what I thought could be useful, but it really depends on what the hardware, driver, and software is capable of. I havn't checked into this, but if you have 3 almost entirely independent radio chains on a single card, would that not mean that you could, in theory, develop a WDS where roaming is entirely seamless? Having all wifi distribution traffic go through a single vlan to a central server that switches the 802.11 traffic into the 802.3 backbone? Then the question becomes, would you be able to separate a single radio chain for roaming and connection discovery? It could have the new connection, to a new AP, with better signal, fully authenticated before the previous (poorer signaled) connection is interrupted. Furthermore, you could simply configure it for a layer 2 notification, to now send all layer 2 packets destined for this layer3 address through this route instead (maybe by a gratuitous ARP or a ping type packet to the WDS Server?) - Meaning no more interruptions while roaming between nodes....

That is, provided the wireless nodes in your network support it.

Furthermore, network troubleshooting and analysis would be further simplified. Considering that you require 2 full channels on either side of the centre channel in order to not interfere with neighbouring networks, that interference could work in your favour when doing network analysis. With a 4x4 radio chain, you could potentially configure each radio chain to listen to a different channel, and catch all overlapping channel traffic too, getting a much faster, much clearer picture of the entire topology of the area that updates more frequently with less work on the hardware side.

I mean, the possibilities here are awesome. No more frequency hopping and incessant probing to try and find your AP.

Of course, the beamforming and everything else included in the 802.11n specification are also nice; and yes, they rely on the MIMO underpinnings to work, but that type of benefit, I believe, would be second to this... at least from a network adminstration point of view.

That's just my thoughts on it. I might be way off base or key, but I find this to be rather exciting. I know they're already working on the next standard, so we'll see.