11-23-2014 09:14 AM - edited 07-05-2021 02:00 AM
Hi all!
I’m trying to set 2,4ghz radio to use 802.11n only, but AP tells me that I must choose one of data rates 6, 9, 12, 18, 24, 36, 48, or 54 Mbit/s. I confused. Aren’t those data rates for 11g?
I want to enable only MCS Rates 1-15 which is 11n.
Now my radio in mixed mode. How to change it to native 802.11n mode to get benefits of N?
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11-23-2014 10:36 AM
You cannot do that. 802.11n mandatory to be backward compatible & you have to enable at least one 802.11a/g data rate.
HTH
Rasika
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11-26-2014 06:52 PM
Actual average speed is 2-3 mbytes.
So you are getting 16-24Mbps in average. is that correct ? If you have that many clients on a single AP, I think this average value is reasonable.
You have told that “802.11n mandatory to be backward compatible” Is it requirement only for cisco APs and there is another vendors which are able to enable strictly 802.11N without backward compatibility?
This is not Cisco restriction, It is defined by IEEE standard & all vendor 802.11n implementation follows that.
To get better throughput in 5GHz, you can enable channel bonding as well. In AP CLI, it is like this.
interface Dot11Radio1
channel width 40-above
HTH
Rasika
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11-27-2014 01:55 PM
11-23-2014 10:36 AM
You cannot do that. 802.11n mandatory to be backward compatible & you have to enable at least one 802.11a/g data rate.
HTH
Rasika
**** Pls rate all useful responses ****
11-23-2014 01:23 PM
rasikanayanajith, thanks for clarification!
I will think how to do something with AP to improve performance.
11-23-2014 01:30 PM
What's the exact issue ? How much throughput you are getting ?
Typically I would disable all data rates upto 12Mbps & make 12Mbps mandatory. All other high data rates supported.
If your 802.11n client get good RSSI & SNR, then it will be dynamically set to a MCS rate. Refer below for MCS rates
MCS Index - 802.11n and 802.11ac
For 802.11n, you have to configure following two things & make sure it is the case.
1. Open Auth or WPA2/AES
2. WMM to be enable.
HTH
Rasika
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11-25-2014 05:12 AM
Thanks for guidelines. Yes I have enabled 11n properly.
My AIR-AP1252AG-E-K9 has 6 antennas.
In total I have about 55 associations.
36 clients use 2,4ghz and 17 clients use 5ghz.
15 clients are laptops. Another 40 are phones and they don’t use Wi-Fi actively.
Now I disabled rates up to 12Mbps & make 12Mbps mandatory as you mentioned above. Definitely it feels better.
Actual average speed is 2-3 mbytes.
You have told that “802.11n mandatory to be backward compatible” Is it requirement only for cisco APs and there is another vendors which are able to enable strictly 802.11N without backward compatibility?
11-26-2014 06:52 PM
Actual average speed is 2-3 mbytes.
So you are getting 16-24Mbps in average. is that correct ? If you have that many clients on a single AP, I think this average value is reasonable.
You have told that “802.11n mandatory to be backward compatible” Is it requirement only for cisco APs and there is another vendors which are able to enable strictly 802.11N without backward compatibility?
This is not Cisco restriction, It is defined by IEEE standard & all vendor 802.11n implementation follows that.
To get better throughput in 5GHz, you can enable channel bonding as well. In AP CLI, it is like this.
interface Dot11Radio1
channel width 40-above
HTH
Rasika
**** Pls rate all useful responses ***
11-27-2014 07:40 AM
Thanks for spend you time!
11-27-2014 08:05 AM
Is like to add a few comment for clarification.
1 the standard for 802.11n states that legacy, mix and green field preambles are supported. However cisco, like many other vendors support legacy amd mix. This is why you can have just 802.11n MCS rates. I'm other words, with mix you will support n ame atleast one legacy PHY. Ras this is indeed a cisco thing not a standard. If it was a standard then explain the greenfield preamble :)
2 you have 6 antennas but 3 are for 2.4 and 3 are for 5 ghz. Your biggest bottles neck will always be medium contention when you have a properly designed network. The more clients on channel the slower she will be. Everyone has to share the medium.
11-27-2014 11:16 AM
Hi George,
Ras this is indeed a cisco thing not a standard. If it was a standard then explain the greenfield preamble :)
This is why I like you spending more time on this CSC, every time I learn something.from your response.
Yes, Greenfield HT, you do not want to have backward compatibility, but question is does any vendor implement that ?
Rasika
11-27-2014 11:33 AM
Enterprise gear I looked at does legacy and mix preamble .. No support for greenfield ht only ..
It's all about the details :)
11-27-2014 11:37 AM
Vendors implementation of 802.11n and 802.11ac pick and choose what they want to implement .. Think of a list to ouck and choose from and yiu as Cisco can pick and choose different components ..
11-27-2014 01:00 PM
Let me add ... Don't confuse using higher phy rates... RTS/CTS and nav timers are used to quite down the legacy clients once quite the ht clients will punch frames but they still use the mix preamble .. So legacy client can back off ..
Does does that make sense ?
11-27-2014 01:22 PM
Yes all that make sense :)
I would like to clarify this from you.
1. This is from 9.23.2 from IEEE 2012 standard, I understood this (may be wrong) as if no protection mode mean they can use green field PPDU, if protection enabled then has to use mixed-mode PPDU.
The HT Protection field may be set to no protection mode only if the following are true: — All STAs detected (by any means) in the primary or the secondary channel are HT STAs, and — All STAs that are known by the transmitting STA to be a member of this BSS are either — 20/40 MHz HT STAs in a 20/40 MHz BSS, or — 20 MHz HT STAs in a 20 MHz BSS.
2. What are the differences in HT protection mode enabled PPDU & protection mode disabled PPDU ?
Rasika
11-27-2014 01:55 PM
11-27-2014 01:58 PM
Remember STA also means access points ..
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