Is there a significant performance benefit to disabling A/B/G WiFi? (N/AC only)

[Ichinisan]

I'm in an apartment complex with dozens of neighboring WiFi networks, so I connect WiFi devices to the 5GHz network whenever possible. All the WiFi devices I care about use dual-band N or AC wireless already. I doubt anyone will ever need to use a wireless-G mobile phone or tablet with my WiFi.

When no A/B/G devices are connected to the network, is there still any performance impact from leaving legacy compatibility enabled?

 

[Ichinisan]

If it matters, my router is the Apple AirPort Extreme 802.11ac (I think it's a Broadcom chipset).

• High-end PC (802.11ac, always wired unless I'm testing WiFi)
• 2x iPhone 6 Plus (802.11ac)
• iPad mini retina 2nd gen (802.11n)
• Apple TV 3rd gen (802.11n)
• Brother's Alienware m11x r3 laptop with upgraded WiFi module (probably N, probably dual-band)

These are the only G devices I have:

• Original 60GB PS3 - Never online because it has hackable firmware and I don't want to update. I'd use a wired connection if I ever go online.
• Wii - I don't plan to put this online again unless I'm playing around with firmware hacks, and I'd probably use a wired USB Ethernet adapter for that.
• Brother HL-2170W B&W laser printer - Exclusively wired now because it started losing all WiFi settings regularly (after years of reliable use).

 

[imagoon]

Define performance.

We disable legacy B speeds (1,2,5.5) to improve device hand off performance.

 

[Ichinisan]

Define performance.

We disable legacy B speeds (1,2,5.5) to improve device hand off performance.

Well, that's what I'd like to know.

Does a G device slow down the entire 2.4GHz band to wireless-G speeds? Does MIMO avoid this somewhat?

Would disabling A/B/G support enhance performance in other ways? Hypothetically (and I'm talking out of ignorance here), I know that even B/G networks change modulation/throughput based on signal strength. Perhaps a wireless-N network supports some kind of modulation that would allow a wireless-N device on the edge of the network range to maintain a reliable connection or keep higher throughput than G-wireless at the same signal strength, but that modulation mode can't be used for the 2.4GHz wireless-N network because it's maintaining compatibility with wireless-B devices that don't support that modulation type.

I'm curious about *any* performance impact (reliability, range, throughput).

 

[azazel1024]

DO NOT!

If you disable it with surrounding 11b/g networks, it disable a number of compabitility bits that are needed for your network to operate properly with everyone elses'. If you are in a quite network environment, where it is pretty much only your network, then disabling can sometimes improve things a little. A lot has to do with WHAT your router is doing by disabling 11a/b/g. If it is only allowing devices to connect with 11n/ac rates, no worries, if it is disabling the legacy compatibility bits (which some do do), this is an issue.

Things that can improve performance that break compatibility are LDP, greenfield mode, SGI, faster beacon rate. SGI is connection specific and doesn't really break the older modes, because the router will fall back to standard guard intervals when legacy clients are connected. Greenfield mode breaks compatibility with older protocols completely if that is enabled. LDP AFAIK depends again on the client. Faster beacon rate breaks 11b and if high enough breaks 11a/g.

A typical 1Mbps beacon rates for 11b compatibility, each SSID and access point on an SSID uses roughly 2.5% airtime for beaconing. So obviously increasing the beacon rate can drastically reduce how much air time a bunch of APs/SSIDs can suck up.

Switch to 11Mbps beacon rate and you can have ~10 Access points or SSIDs on the same channel only using 2.5% of your air time. If you used the standard 1Mbps beacon rate, you'd be sucking down 25% of your airtime (or more).

This is partly why congested apartment complexes wireless sucks so bad. Even if everyone elses' networks were not in use, all of the beaconing can really cut down on free airtime.

As for your question on modulation modes, no, not really. Modulation is more or less directly related to signal strength. 11b uses CCK and not OFDM like 11a/g/n/ac.

That said, if working PROPERLY, if the signal strength is low enough, even 11a/g/n/ac will drop OFDM at low data rates and use CCK (or DSSS for REALLY low data rates). Your success will vary. My experience is that for absolute MAXIMUM range, 11b tends to work a little better than using 11a/g/n/ac and allowing the modulation rate to drop. Of course performance at most ranges is massively inferior. We are talking it might be better to use 11b if setting up a 10 mile wifi link using directional antennas.

Otherwise, newer protocols and let it change the modulation scheme on the fly.

With mixed clients, the base station will transition protocols/modulation schemes as appropriate between the clients seamlessly. The biggest issue is with 11n with some of the "11n only" stuff which is not backwards compatible.


That said, transitioning between protocols/modulation schemes has a negative impact on overall performance. So mixing in some 11g clients on an 11n/ac network is going to have a much larger negative impact than mixing 11n clients on to an 11ac network.

 

[Ichinisan]

DO NOT!

If you disable it with surrounding 11b/g networks, it disable a number of compabitility bits that are needed for your network to operate properly with everyone elses'. If you are in a quite network environment, where it is pretty much only your network, then disabling can sometimes improve things a little. A lot has to do with WHAT your router is doing by disabling 11a/b/g. If it is only allowing devices to connect with 11n/ac rates, no worries, if it is disabling the legacy compatibility bits (which some do do), this is an issue.

Things that can improve performance that break compatibility are LDP, greenfield mode, SGI, faster beacon rate. SGI is connection specific and doesn't really break the older modes, because the router will fall back to standard guard intervals when legacy clients are connected. Greenfield mode breaks compatibility with older protocols completely if that is enabled. LDP AFAIK depends again on the client. Faster beacon rate breaks 11b and if high enough breaks 11a/g.

A typical 1Mbps beacon rates for 11b compatibility, each SSID and access point on an SSID uses roughly 2.5% airtime for beaconing. So obviously increasing the beacon rate can drastically reduce how much air time a bunch of APs/SSIDs can suck up.

Switch to 11Mbps beacon rate and you can have ~10 Access points or SSIDs on the same channel only using 2.5% of your air time. If you used the standard 1Mbps beacon rate, you'd be sucking down 25% of your airtime (or more).

This is partly why congested apartment complexes wireless sucks so bad. Even if everyone elses' networks were not in use, all of the beaconing can really cut down on free airtime.

As for your question on modulation modes, no, not really. Modulation is more or less directly related to signal strength. 11b uses CCK and not OFDM like 11a/g/n/ac.

That said, if working PROPERLY, if the signal strength is low enough, even 11a/g/n/ac will drop OFDM at low data rates and use CCK (or DSSS for REALLY low data rates). Your success will vary. My experience is that for absolute MAXIMUM range, 11b tends to work a little better than using 11a/g/n/ac and allowing the modulation rate to drop. Of course performance at most ranges is massively inferior. We are talking it might be better to use 11b if setting up a 10 mile wifi link using directional antennas.

Otherwise, newer protocols and let it change the modulation scheme on the fly.

With mixed clients, the base station will transition protocols/modulation schemes as appropriate between the clients seamlessly. The biggest issue is with 11n with some of the "11n only" stuff which is not backwards compatible.


That said, transitioning between protocols/modulation schemes has a negative impact on overall performance. So mixing in some 11g clients on an 11n/ac network is going to have a much larger negative impact than mixing 11n clients on to an 11ac network.

That helps a lot. Thank you!

 

[imagoon]

DO NOT!

If you disable it with surrounding 11b/g networks, it disable a number of compabitility bits that are needed for your network to operate properly with everyone elses'. If you are in a quite network environment, where it is pretty much only your network, then disabling can sometimes improve things a little. A lot has to do with WHAT your router is doing by disabling 11a/b/g. If it is only allowing devices to connect with 11n/ac rates, no worries, if it is disabling the legacy compatibility bits (which some do do), this is an issue.

Things that can improve performance that break compatibility are LDP, greenfield mode, SGI, faster beacon rate. SGI is connection specific and doesn't really break the older modes, because the router will fall back to standard guard intervals when legacy clients are connected. Greenfield mode breaks compatibility with older protocols completely if that is enabled. LDP AFAIK depends again on the client. Faster beacon rate breaks 11b and if high enough breaks 11a/g.

A typical 1Mbps beacon rates for 11b compatibility, each SSID and access point on an SSID uses roughly 2.5% airtime for beaconing. So obviously increasing the beacon rate can drastically reduce how much air time a bunch of APs/SSIDs can suck up.

Switch to 11Mbps beacon rate and you can have ~10 Access points or SSIDs on the same channel only using 2.5% of your air time. If you used the standard 1Mbps beacon rate, you'd be sucking down 25% of your airtime (or more).

This is partly why congested apartment complexes wireless sucks so bad. Even if everyone elses' networks were not in use, all of the beaconing can really cut down on free airtime.

As for your question on modulation modes, no, not really. Modulation is more or less directly related to signal strength. 11b uses CCK and not OFDM like 11a/g/n/ac.

That said, if working PROPERLY, if the signal strength is low enough, even 11a/g/n/ac will drop OFDM at low data rates and use CCK (or DSSS for REALLY low data rates). Your success will vary. My experience is that for absolute MAXIMUM range, 11b tends to work a little better than using 11a/g/n/ac and allowing the modulation rate to drop. Of course performance at most ranges is massively inferior. We are talking it might be better to use 11b if setting up a 10 mile wifi link using directional antennas.

Otherwise, newer protocols and let it change the modulation scheme on the fly.

With mixed clients, the base station will transition protocols/modulation schemes as appropriate between the clients seamlessly. The biggest issue is with 11n with some of the "11n only" stuff which is not backwards compatible.


That said, transitioning between protocols/modulation schemes has a negative impact on overall performance. So mixing in some 11g clients on an 11n/ac network is going to have a much larger negative impact than mixing 11n clients on to an 11ac network.

Mean while, we experience the complete opposite. Leaving legacy B speeds on, like 1, 2,5.5Mb destroys the performance of the network, causes poor hand offs and generally make the clients act like crap.

 

[RadiclDreamer]

I also disable legacy speeds to improve performance. This was recommended to me by a cisco wireless CCIE, it has not caused any adverse issues.

 

[azazel1024]

I personally disable 11a/b/g on my home network, but I also don't have any surrounding networks in range. If I had a bunch, I'd leave the legacy stuff enabled because it greatly reduces the odds of conflicts if anyone is bringing 11a/b/g stuff to the table on their own network.

These days, 11b is probably rare enough that you can safely disable that, but 11g is unfotunately still pretty common.

 

[imagoon]

I personally disable 11a/b/g on my home network, but I also don't have any surrounding networks in range. If I had a bunch, I'd leave the legacy stuff enabled because it greatly reduces the odds of conflicts if anyone is bringing 11a/b/g stuff to the table on their own network.

These days, 11b is probably rare enough that you can safely disable that, but 11g is unfotunately still pretty common.

I would like to see information on why you say this if you have it. One of my offices is in the Chicago Loop next door to the Sears / Willis / Big Willie tower. When I walked the floor with the wireless detector / spectrum analyzer, I picked up no less that 315 APs. I still disabled the legacy B 1 -5.5 and performance improved drastically esp AP to AP hand offs.

 

[azazel1024]

Yes...I mentioned that 11b is rare enough you can probably safely disable it. That isn't going to impact anything in a negative way unless there are 11b clients running. Having other routers which have 11b enabled isn't going to impact your's at all, it is only if there are active 11b "sessions" going on that it can cause problems for you.

disabling 11g compatibility is likely to cause issues either for your network or certainly for networks and clients that are 11g only (I am refering to 11g clients on other surrounding wifi networks). Now if there were no 11g clients/networks near your network, disabling 11g would likely speed things up some as well.

 

[Fardringle]

Why would disabling G compatibility on your router have any negative effect on your network OR on neighboring networks if you don't have any G clients? If anything it will HELP as your network will no longer be broadcasting on those frequencies and therefore not interfering with any neighboring clients/networks.

 

[Ichinisan]

Why would disabling G compatibility on your router have any negative effect on your network OR on neighboring networks if you don't have any G clients? If anything it will HELP as your network will no longer be broadcasting on those frequencies and therefore not interfering with any neighboring clients/networks.

B/G/N all use the same 2.4GHz band and channels.

 

[imagoon]

Yes...I mentioned that 11b is rare enough you can probably safely disable it. That isn't going to impact anything in a negative way unless there are 11b clients running. Having other routers which have 11b enabled isn't going to impact your's at all, it is only if there are active 11b "sessions" going on that it can cause problems for you.

disabling 11g compatibility is likely to cause issues either for your network or certainly for networks and clients that are 11g only (I am refering to 11g clients on other surrounding wifi networks). Now if there were no 11g clients/networks near your network, disabling 11g would likely speed things up some as well.

I didn't disable 802.311b. Do you have any information about why you are saying this? I am really confused about what you are trying to tell me as it doesn't generally reflect my experiences in the field.

 

[azazel1024]

You just said you disabled legacy rates of 1-5.5Mbps. That WILL break 11b compatibility if anything is running 11b. 11b requires 1Mbps per spec. So, you might not be specifically toggling a drop down that says "11g/n only", but you are in effect disabling 11b Imagoon. 11b is rare, so disabling things that prevent it from working is often not an issue. Though you will have issues at extreme range from your network, as it means that clients/router cannot drop down to 1/2/5.5Mbps at extreme range (lower the modulation rate, the longer the range because of increased SINR performance).

As for why disabling 11g functionality can impact your network, if no one is running 11g around you, it doesn't. If someone is, 11n uses things that are NOT backward compatible to 11g and vice versa. If you have 11g/n running, no worries. If you have 11n only, then you'll be running your network in such a way that is it not compatible with 11g.

That means, in effect your network will not see an 11g network. Wifi networks (11a/g/n/ac, 11b is not OFDM, but it is CD) operate using OFDM-CD. Ignore the OFDM part, the CD is "with Collision Detection". If your 11n network cannot see an 11g network, it CANNOT coorrdinate "Clear to Send" messages.

So instead of congenially (in theory) coordinating their talk time, the two networks will be blind to each other, but that doesn't mean that they aren't still trying to talk over each other. It GREATLY increases interference because of a lack of coordination (same issue as the hidden node problem, when a client can see/hear two routers on different networks, but the routers can't see/hear each other).

 

[imagoon]

You just said you disabled legacy rates of 1-5.5Mbps. That WILL break 11b compatibility if anything is running 11b. 11b requires 1Mbps per spec. So, you might not be specifically toggling a drop down that says "11g/n only", but you are in effect disabling 11b Imagoon. 11b is rare, so disabling things that prevent it from working is often not an issue. Though you will have issues at extreme range from your network, as it means that clients/router cannot drop down to 1/2/5.5Mbps at extreme range (lower the modulation rate, the longer the range because of increased SINR performance).

As for why disabling 11g functionality can impact your network, if no one is running 11g around you, it doesn't. If someone is, 11n uses things that are NOT backward compatible to 11g and vice versa. If you have 11g/n running, no worries. If you have 11n only, then you'll be running your network in such a way that is it not compatible with 11g.

That means, in effect your network will not see an 11g network. Wifi networks (11a/g/n/ac, 11b is not OFDM, but it is CD) operate using OFDM-CD. Ignore the OFDM part, the CD is "with Collision Detection". If your 11n network cannot see an 11g network, it CANNOT coorrdinate "Clear to Send" messages.

So instead of congenially (in theory) coordinating their talk time, the two networks will be blind to each other, but that doesn't mean that they aren't still trying to talk over each other. It GREATLY increases interference because of a lack of coordination (same issue as the hidden node problem, when a client can see/hear two routers on different networks, but the routers can't see/hear each other).

Again, this doesn't match my experience. Old B devices can connect fine to the networks with 1 - 5.5 disabled, we have scanners and the like that do it everyday. Only thing I have seen is typical Apple product BS with things like MS0 support which is more a hardware issue on the Apple side than anything else.

Also I am not seeing the requirement for B and G support for the Wireless N coexistance functions to operate in the standard. This is why I keep asking for information (links / support / otherwise) because it is not matching my experiences or the documentation I have read in the past. Everything I have read indicates that N coexistence tech like you are mentioning is baked in to the PHY and does not specifically require that the AP support B or G even in a noisy environment. However I am interested in documentation on the subject.

 

[azazel1024]

http://en.wikipedia.org/wiki/IEEE_802.11n-2009

Just go down to the section on Backward compatibility. In some cases, a network with "802.11g/n only" or "802.11n only" are ONLY setting the WAP up so that it will allow connections by devices supporting that only. In some cases, they change nits that will break compatibility with older devices.

Changing so that 1-5.5Mbps is disabled is apparently only telling the basestation to not use those modulation rates. In some cases, depends on the WAP, it can also be forcing the WAP to use a >5.5Mbps beacon rate, this WILL break 802.11b compatibility. 11b devices can only see a 1Mbps beacon.

For 802.11n only, it can also mean that greenfield mode gets enabled. Again, read under the compatibilty there for the 2009-802.11n specifications. This will break 802.11a/b/g clients ability to connect to the network and it will also cause interference for surrounding non-802.11n capable networks.

 

[imagoon]

http://en.wikipedia.org/wiki/IEEE_802.11n-2009

Just go down to the section on Backward compatibility. In some cases, a network with "802.11g/n only" or "802.11n only" are ONLY setting the WAP up so that it will allow connections by devices supporting that only. In some cases, they change nits that will break compatibility with older devices.

Yes it makes sense that if the AP doesn't properly support the protocol it would have issues. I would also assume in "g/n only" that a and b would fail. "n only" I would expect g to fail.

Changing so that 1-5.5Mbps is disabled is apparently only telling the basestation to not use those modulation rates. In some cases, depends on the WAP, it can also be forcing the WAP to use a >5.5Mbps beacon rate, this WILL break 802.11b compatibility. 11b devices can only see a 1Mbps beacon.

As mentioned I disabled the legacy b speeds. The beacons are set to default. The APs still "support" the speed but send a disassociate when the device trys to connect at those speeds which prompts them to reconnect to a strong AP.

For 802.11n only, it can also mean that greenfield mode gets enabled. Again, read under the compatibilty there for the 2009-802.11n specifications. This will break 802.11a/b/g clients ability to connect to the network and it will also cause interference for surrounding non-802.11n capable networks.

For this part I would say "as expected." In N only, I would never expect a,b,g to function. Any signal on the spectrum that wasn't N would be noise, which is expected. However this doesn't block the AP from using guards. I would also expect the N network to react to the noise per the specifications. Similar how 802.11b did it years ago when it needed to share.

 

[Ichinisan]

I remember being confused by Nintendo's instructions for connecting the original Nintendo DS with the DI-524 wireless router.

The Nintendo DS was 802.11b only and only supported WEP encryption. Maybe it had WPA support encapsulated in AOSS push-button pairing, but I can't be sure about that. the Nintendo Wi-Fi Connection compatibility guide said to change the DI-524 to wireless G mode to resolve the compatibility problem. Somehow, that actually worked.

 

[azazel1024]

Yes it makes sense that if the AP doesn't properly support the protocol it would have issues. I would also assume in "g/n only" that a and b would fail. "n only" I would expect g to fail.


As mentioned I disabled the legacy b speeds. The beacons are set to default. The APs still "support" the speed but send a disassociate when the device trys to connect at those speeds which prompts them to reconnect to a strong AP.



For this part I would say "as expected." In N only, I would never expect a,b,g to function. Any signal on the spectrum that wasn't N would be noise, which is expected. However this doesn't block the AP from using guards. I would also expect the N network to react to the noise per the specifications. Similar how 802.11b did it years ago when it needed to share.

The difference on interference is it means that 802.11n has to fall back on using CTS/RTS, which reduces throughput, very significantly if the other network has a lot of traffic and is reasonably strong comparred to your network and vice versa.

 

[imagoon]

The difference on interference is it means that 802.11n has to fall back on using CTS/RTS, which reduces throughput, very significantly if the other network has a lot of traffic and is reasonably strong comparred to your network and vice versa.

"Fallback?" It already uses it.