801.11ac MCS rates and 10 or 5Mhz channel width

RouterOS Wireless Networking
1

For interference avoidance reason I am reducing the bandwidth of my AP networks to 10Mhz, and even looking to 5Mhz.
It also increase a bit the signal strengths so higher MCS rate can be obtained.

The downside is that 10Mhz only have half the throughput as 20 Mhz and 5Mhz even half of the 10 Mhz.
So to still have reasonable throughput in the 5mhz (or 10 Mhz) you need MCS rates of 13, 14 or best, 15.

But what about 802.11ac in 5mhz? I can’t find any MCS rates graphs that actually show the rate for these bandwidths.
Is it not possible or is it just not mentioned since everybody thinks nobody want’s to use it?

And would an ac radio give the same or better throughput compared to ‘an’ if the signals are the same and thus the MCS rates are the same?

(In other words; If I would have a link working with MCS 14 with a ‘n’ mimo radio and station, to replace both for an ‘ac’ radio but all other parameters the same, would it have better throughput or it is just the same? )

2

Our AC boards doesn’t support 5/10mhz channel width.

3

And even at 20 MHz you cant get the highest modulation. Wikipedia has a table.

4

On 20mhz it is possible if you use 3chains.

5

So your cards can do 256-QAM 5/6 on a 20MHz Channel with 3 streams?

The table there http://en.wikipedia.org/wiki/IEEE_802.11ac
says you need 40MHz to get 256-QAM 5/6 with 802.11ac.

6

Yes, why is 5/6 coding in 256-QAM (MCS9/17/25) not possible in 20Mhz channel? Must be something technical but maybe some can explain in plain language..

7

And why no 10Mhz support in ac? It hit me now in migrating some parts of my networks into new ac units. Suddenly I can’t use them everywhere because some of my networks do work on 10Mhz only just to reach that last mile client. (And to withstand close band interference from the competition.)
Is this something the chipset doesn’t support? Or the protocol doesn’t allow? Or just the ROS for ac is forgot to have it enabled?

I had it on SEXTANTs before it didn’t work and that was corrected in next ros release at the time…