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This question is related to Wifi devices and is of two parts.

I am wondering if one buys a 802.11n conforming station, does it mean that it is able to behave as a 802.11g or 802.11a station if it exisits within 802.11a or g basic service set?

If yes, can someone explain or give me references why?

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    – Ron Maupin ♦
    Aug 11, 2017 at 17:34

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First of all 802.11g is 2.4Ghz only and 802.11a is 5GHz only. If you don't have a dual band client (a+g) it can only connect to g OR a depending on what band your client supports.

802.11n can do both 2.4GHz (gn) and 5GHz (an) depending on your AP.

A 2.4GHz 802.11n (gn) device can always behave as a 802.11g device because the n only means bigger channel width (40MHz) and up to four spatial streams. But it can revert back to using just one spatial stream if there is a 802.11g client.

The same is true for a 5GHz 802.11n (an) device, it can also revert back to fewer streams if needed.

Please have a look at: https://en.wikipedia.org/wiki/IEEE_802.11n-2009

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  • Your answer is a little confusing. 802.11g is 2.4 GHz-only, and 802.11a is 5 GHz-only. A 5 GHz-only AP would not allow an 802.11g device to connect.
    – Ron Maupin ♦
    Jul 7, 2015 at 15:07
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    Also, N is different signal encoding, not just a wider channel.
    – Ricky
    Jul 7, 2015 at 20:58
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    Full agreement with Ricky. There are far more improvements in 802.11n than wider channel and more spatial streams. Besides his addition of modulation/encoding, there is MIMO (which is more than just additional spatial streams), frame aggregation, block acks, and so on.
    – YLearn
    Jul 7, 2015 at 22:12
  • Sure, but are they relevant to the question?
    – Peter
    Jul 8, 2015 at 6:08
  • Maybe not, but you made the following statement in your answer and it is inaccurate: because the n only means bigger channel width (40MHz) and up to four spatial streams. Although, to be honest, I would probably argue that at least the modulation/encoding is more important to backwards compatibility than spatial streams (and probably 40MHz wide channels, especially in 2.4GHz). Namely because there are plenty of single spatial stream 802.11n devices that never use more than one spatial stream and as such never "go back to using just one spatial stream" for backwards compatibility.
    – YLearn
    Jul 9, 2015 at 3:05
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First, to clarify, the 802.11 standards are proposed and maintained by the IEEE, specifically the 802.11 working group.

Wi-Fi is a trademark of the Wi-Fi Alliance which provides a voluntary certification program for devices to be Wi-Fi Certified. Devices do not need to be Wi-Fi Certified to operate as 802.11 devices.

I am wondering if one buys a 802.11n conforming station, does it mean that it is able to behave as a 802.11g or 802.11a station if it exisits within 802.11a or g basic service set?

It should definitely be able to operate in a 802.11g environment as 802.11n requires 2.4GHz support.

However, 802.11a operates in 5GHz and 802.11n made 5GHz support optional, so there are two possibilities:

  • If you have a single band (only supports 2.4GHz) 802.11n client, it would not be able to operate in an 802.11a environment.
  • If you have a dual band (supports both 2.4GHz and 5GHz) 802.11n client, then it would be able to operate in an 802.11a environment.

I will throw out the caveat that some drivers will allow you to specify which band or bands in which a device will operate. So it logically follows that if you have configured your 802.11n dual band device to only operate in 5GHz, it won't be able to operate in an 802.11g environment (and vice versa).

If yes, can someone explain or give me references why?

Technically speaking, when you see something like 802.11g or 802.11n, these are amendments to the main 802.11 standard. They are typically not standards in and of themselves.

Periodically, the IEEE will incorporate these amendments into the main standard as a maintenance release. The current standard is 802.11-2012, which actually started with the 802.11-2007 standard and incorporated 10 additional amendments, including 802.11n.

So, to answer your question as to why, it is because 802.11a, 802.11g, 802.11n and 802.11ac are all amendments to the standard and need to take into account the standard when written/designed. This includes interoperability with previous devices that adhere to the standard.

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In order to be considered Wi-Fi gear, the wireless LAN equipment must pass inspection / testing ensuring backwards compatability with legacy standards. So, when you see the Wi-Fi logo, you know it is backward compatable. More at Certification Benefits.


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  • Thanks for the reference. By backward compatible, you mean an ac device can behave as n device forexample?
    – Tyrone
    Jul 7, 2015 at 15:27
  • Right. The .ac device can behave as a .n device.
    – Ronnie Royston
    Jul 7, 2015 at 15:35

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