The Brighter Side
On a more positive note, there are also good things that 11ac brings to the party. The slide below from QCA's presentation is a good summary of 11ac's "secret sauces". The previous discussion covered the first three points, so we'll press on to the others.
We've all heard manufacturers tout transmit beamforming as product differentiators. But what they don't tell you is that the form used in 802.11n doesn't really help much because there are multiple versions of it and not everyone uses the same one. The other part of the story is that the client has some work to do to answer back to the AP to help it properly form the beam and most clients don't implement their part.
QCA 802.11ac Key Technical Elements Summary
Source: QCA presentation
Of course, improving effective transmit power on only one end of the connection doesn't do anything to help the client end of the connection. The good thing is that 802.11ac has only one standard for beamforming, so it has a better chance of actually providing performance improvement.
Inquiring minds want to know if 802.11ac will provide improved range. The slide below from the Broadcom presentation referenced earlier indicates that it does. Broadcom's 5G WiFi Primer paper points to beamforming as the responsible technology (Page 4, Range and Coverage Area). (Significant range gain would require proper implementation of transmit beamforming on both AP and client).
802.11n/802.11ac Rate over Range comparison
Source: Source: Broadcom
But on a practical basis, you shouldn't expect any range improvement over what you get from current 5 GHz 11n gear. And don't forget that 11ac is 5 GHz only, so you don't have the option of dropping back to 2.4 GHz and getting the same higher link rates. Note also the steeper rate over range curve, showing highest rates over only a very small distance. But, as with 11n and with good signal levels you should get higher throughput in a given location.
One cute trick that 11ac brings to the table is Multi-User MIMO (MU-MIMO). As the right side of the Agilent slide below shows, MU-MIMO allows receive/transmit pairs to be assigned to different clients. Think of a 3X3 router/AP serving three clients simultaneously with one stream each vs. using a three-stream connection in a round-robin fashion on one client at a time.
Source: Source: Agilent
The advantage will probably be most pronounced for single-stream only mobile clients, which will now have higher link rates available via 11ac's wider bandwidth. Note that MU-MIMO won't be in the first group of 802.11ac products. The QCA slide below shows it as not out until 2014, if the predicted timeline holds.
Source: QCA presentation
11ac is going to be birthed and developed in the market, just as 11n was. The products coming out at the end of this year will be "draft" 11ac and it's too early to tell whether they'll be mature enough to be grandfathered into the final standard.
If you're an early adopter, go right ahead and jump in and wallow around. But if you like your technology a little more baked, you'll probably want to wait until later next year (2013) to take your first plunge. Of course, SmallNetBuilder will be here, as always, as your trusted guide.