currently I have a 802.11a setup with 4 R52 cards in RB435G connected to single-pol antennas. Bandwith is 20 MHz and I’m not using nstreme.
I have clients connecting with:
RB-SXT (dual-pol panel)
RB411 + R52 + single-pol panel
RB711 + single-pol panel
x86 running ROS 3.x with Trendnet TEW-503PI + single-pol antenna
Avg. client throughputs are 10-20 Mbps.
I’d like to increase throughput by switching to dual-pol sectors (AirMax od any other) and R52Hn cards (with nstreme on).
Questions:
Can I use mixed bands (a/n) and how will that work? Clients with RB-SXT and RB711 will connect in 11n and others in 11a?
Can I use 40 MHz bandwith with all mentioned cards (AP: R52Hn, Clients: R52, RB711, Trendnets) in both 11a and 11n standards?
What avg. improvement in throughput can I expect? RB-SXT with 2x2 MIMO will probably have highest speeds, RB711 with 1x1 MIMO little less and 11a clients minimum.
Do you recommend a different setup to replace the current one? My goal is to achieve highest throughput possible with current client equipment.
Question 1 & 3 - Yes, you can use mixed modes of A and N. It works basically the same way a B/G access point works with mixed clients. When a wireless A client is talking to the AP the AP has to switch to a sort of “Protected Mode” which will reduce throughput of the wireless N clients. The real world throughput will change depending on a large number of factors, so it is hard to predict what you will actually see with this setup. Ideally, all clients would be using the same CPE hardware. That having been said, you should still see a performance improvement across the board from what you are using now. Question 2 - Since you are using mixed clients you will have to decide what it is that you want to do, either 802.11 a/n or 40MHz “Turbo A”. You cannot use 802.11N 40MHz channels with 802.11a clients. You could use “Turbo A” 40MHz channels, but that would negate the 802.11n, although nstreme will still work with that. If the card is capable of 802.11n then you will have to use NV2 in order to accomplish the same task and all clients will have to use NV2. Their are pros and cons to using NV2 so try it and carefully weigh the pros and cons. Question 4 - If your goal is to achieve the highest throughput possible then swithing all cleints to 2x2 MIMO will be the best option. Without changing all of your current hardware I would use “Turbo A” with nstreme. This will give you up to 60M/s at the CPE (the processor of each piece of hardware will play a big difference in this) and its very stable. NV2 has some great features, but at the cost of stabilty. 802.11a/n is fine, but it will be better for you not to use a 802.11 standard. The non-standard protocols such as nstreme offer better security over 802.11.
There isn’t much point to 20/40 with A clients in the mix. It will essentially never go to 40MHz.
I use single polarity clients with dual chain AP’s, both antennas in VPOL, works fairly well.
Mixing A and N hardware will limit you to A speeds when that client is active, the same way a weak signal on one CPE will slow down the entire AP. It will work fine, but it will need to be addressed or you will never get full capacity on this AP.
With my setup I am looking for maximum stability with a less than ideal situation, so I disabled MCS08 to 15. It is configured for dual chain but not allowed dual chain speeds. This increases the reliability of the AP with a max speed of 65Mbps or 130Mbps in 40MHz mode. Most of these towers do not have A/B/G clients, though it happens from time to time.
In your situation I’d run dual polarity 20MHz and as finances allow upgrade all clients to dual polarity equipment. That will give significant gains over a mixed system.
I’ve been doing similar and moving my 802.11g equipment to smaller cell AP’s while keeping my long range stuff 802.11N where ever possible.
Unfortunately, since we’re an association and not WISP, we can’t change client equipment. We have to deal with what we have and can only make changes on our side.
@ssofet you suggested switching to 40 MHz on 11a with nstreme on. I’m confused by MikroTik User’s Manual which states that RB711 doesn’t support turbo.
http://routerboard.com/pdf/220/rb711ug.pdf Onboard 802.11a/n 5GHz wireless card
“This RouterBOARD model has a built-in 802.11a/n 5GHz wireless device based on the AR9280 Atheros chipset. It doesn’t support turbo mode.”
If that’s true, we can’t use 40 MHz bandwith. All used devices (list is in 1st post) have to be able to connect.
Also, is there any need for R52Hn or any other card that’s more sensitive then R52?
I’ve had decent luck with the R52Hn, just a few of them out there. I recommend testing on the ground for a week or so before putting them up. Had a board burn out after a few days. Seems that MT has sorted the problems out, but it is always best to stress the equipment before mounting it on a tower. I am leaning towards the R52N-M myself. Self interference on a tower sucks and seems to be less of an issue with weaker cards.
None of the 802.11N hardware will work with the old 40MHz turbo, just not compatible on the hardware level.
You have a bit of a growth problem with limited control over the CPE. This will prevent you from tripling your capacity and/or speeds.
Maybe it has been added in the AR9280 chipset. That would be nice to hear, but as far as I know all 802.11n chipset from Atheros cannot do standard 40MHz turbo.
Can you try it? My RB711 took a dive this weekend, nasty storm.
RB411 and RB600 R52 boards originally with 5GHz nv2 and 20MHz bw. swithing to 40MHz bw fully failed, big warning!
We did switch to 40Mhz bw. several of the antennas did never come up on the network again, not even after switching back to 20Mhz that come back on net.
We needed to power cycle all antennas in that sector.
