Why is my wifi faster with 802.11n in 802.11a compatible mode?
February 12, 2015 10:16 PM   Subscribe

Cable modem, Time capsule, and various Macs. When I put the time capsule into 802.11n only mode, I get about 30mbps. When I put the time capsule into 802.11n (a compatible) mode, I get about 60mbps. Why could that be?

I have a number of related issues:
I have an older (2008) iMac, Time Capsule and some newer Macbooks and an HP printer. All of these devices say they are 802.11a/b/g/n compatible, except the printer which says it is n/b/g only.
When I put the time capsule into 802.11n only mode, I get about 30mbps.
When I put the time capsule into 802.11n (a compatible) mode, I get about 60mbps - but the printer cannot connect.
When I put the time capsule into 802.11n (b/g compatible) mode, I get about 10mbps

So - why are the speeds so different, since theoretically all these devices should be using n?
Also why can't the printer connect in a-compatible mode, while it can connect in n-only?

I'm fairly technical, but radio/networking is not my thing. I'm just looking for possible reasons here, as my simple workaround is going to be taking the printer off the wifi network and running in the a-compatible mode which is fastest. I can print to the printer via USB or ethernet, I guess.

Oh, and unplugging the printer seems to have no effect on the speeds. Just the radio mode.
posted by bashos_frog to Computers & Internet (7 answers total)
 
You're basically telling your Time Capsule to use the 5GHz band (a-compatible) instead of the 2.4GHz band (b/g compatible). The 5GHz band usually offers faster speeds because it's generally less crowded and base stations will default to a 40MHz channel width (basically using two channels worth of bandwidth to increase speed). The downside is that some older/cheaper equipment isn't dual-band capable, as you've found with your printer. Also the 5GHz band has less range, but not having to deal with the crowded 2.4GHz band is worth it.
posted by zsazsa at 10:31 PM on February 12, 2015 [3 favorites]


The disadvantage is that there are a lot of devices which can speak 2.4 GHz but cannot speak 5 GHz. That doesn't appear to be happening to you, but keep in mind that it is possible.
posted by Chocolate Pickle at 11:03 PM on February 12, 2015


Ah, is that so? I thought they were all 2.4. (It is a, not ac) I can check this later when my Kindle charges, since they can't use 5ghz.
If that's the case, can I also use the Airport Express I have laying around to provide a separate 2.4ghz access point? I'd love to get it all working together somehow.
posted by bashos_frog at 11:32 PM on February 12, 2015


I don't have my older airport extreme or time capsule of the dual band/N generation like what you're probably talking about anymore, and my memory is a bit fuzzy, but isn't there some i-dont-care option to the effect of "automatic"? Because apples routers are some of the *only* ones i've had decent luck with just leaving everything set to full auto or the defaults on, and a crappier experience when i tried to tweak it too much.

Are there options for a 5ghz network name? New(er, ish) time capsules should support making separate 2.4ghz wireless N and 5ghz N networks. Then you could make one like "bashos-computers" on 5ghz and "bashos-printers and old stuff" on 2.4ghz. Then you get the better speeds and your printer or any random devices that wont play nice can hop on the old network. If you don't see that option, then it's an older time capsule that can only do 2.4 or 5ghz. In which case, yea, you're probably just going to have to live with the 30mbps-ish speeds of the n only mode.

For what it's worth, i wonder if you're getting lots of environmental interference though. My airport extreme of that era had no problem pushing out ~60mbps on the 2.4ghz band, anywhere in my decent sized bunker-walled apartment. I have had issues with slow wifi speed on 2.4ghz, and it was in a crappy house with crappy wiring and lots of junky electronicy things and cheap CFL lights spewing out lots of electrofarts. Maybe try repositioning the router in N mode? 30mbps is pretty crappy for one of those, they have more gumption than that usually.

Oh, and shoutout to the fact that i really really hate how apple keeps dumbing down the descriptions of stuff in airport utility more and more. Even the setup screens on a wii are more descriptive, and that's literally made to be set up by tweens. It used to be verbose about 2.4 or 5ghz, and now it's like "n compatible" and "a compatible" fuuuuuck you guys.

As a side note, i played around with this idly for a while in various modes on my stuff... and then bought a wireless AC airport. I have 100mbps~ internet, and i can pull down 120mbps or more over AC on my nexus 5, or my retina macbook. Even wireless N stuff gets stronger signals and more performance than it used to. On 2.4ghz too! And i get to use channel bonding/simultaneous 2.4+5ghz on stuff that supports it. Latency AND throughput improved even on N devices. It feels like the upgrade from good 3G to early LTE when there weren't tons of people shitting up the airwaves and it was just like zomgfast. If you get tired of dealing with this, maybe it's time for a simultaneous dual band router, if not an AC router?
posted by emptythought at 2:41 AM on February 13, 2015


So, I think I solved it. I've connected the Airport Express via ethernet cable to the Time Capsule, and put it into "Create a Network" rather than "Extend a Network". This gave me the option to choose 802.11n (only) in the 2.4gHz band. Both of them are using the same SSID and password, so devices should just choose the best one that's available to them. My printer is connected to wifi, and I can print to it, even though I am using the other (5gHz) access point.

Range isn't an issue, as I'm in a 2br, with, at most, 2 walls between me and access point at any time.

(and I agree that all the dumbing-down actually makes things harder to understand for people with different use cases than the majority)
posted by bashos_frog at 7:28 AM on February 13, 2015


I have an older (2008) iMac, Time Capsule and some newer Macbooks and an HP printer. All of these devices say they are 802.11a/b/g/n compatible, except the printer which says it is n/b/g only.

I think - and my understanding may be out of date by now - that a WiFi network operates at the speed of the slowest device on it. So your printer, by joining the network, is slowing everyone down so that it can keep up.

That's easy to test - go back to the configuration where you'd get 30mbps, but with the printer switched off. (So, never have the printer join the network after you switch configurations - that's different from switching it off after you've already been slowed down.) What's your speed? I bet you're back up at 60 mbps.

In any case, the solution would be exactly what you've found - use two networks and keep the slow device on the slower network.

(Also, the new dual band ac Airport Extreme is pretty great - it handles a lot of these issues out of the box.)
posted by RedOrGreen at 2:52 PM on February 13, 2015


All the dumbing-down actually makes things harder to understand for people with different use cases than the majority

Alas, absolutely true, but on Apple's scale, people like us with some technical competence and odd use cases just don't count. Do it their way or fend for yourself. On the plus side, they do make it more possible to do odd things these days - at least on some fronts.
posted by RedOrGreen at 2:56 PM on February 13, 2015


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