General Question

andrew's avatar

Does a 802.11n router's speed decrease if g or b devices connect to it?

Asked by andrew (16358points) February 17th, 2008

I vaguely remember that being the case with 802.11g routers… if an a or b device were to connect wirelessly, then all devices would suffer. Will my new time capsule be limited by my xbox360?

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7 Answers

paulc's avatar

My understanding is that if a router is operating in g/n compatibility mode there will be a loss in speed compared to it being solely in n mode. I don’t know for certain if the n-able devices will slow down to g speeds but that’s how it worked with b/g compatibility (g-able devices had b speeds). I guess the best way to maximize your speeds would be to use both your curent router and time capsule simultaneously since n can run on 2.4gHz or 5gHz. That is assuming that you can specify which band the time capsule will run on.

andrew's avatar

Ah…. So I’d just hardwire my old router to the timecapsule. Smart.

spacejam's avatar

it depends a lot on how many devices you are talking here

samkusnetz's avatar

nope nope nope. putting even a single device on the network that uses “a”, “b”, or “g” will bring the whole system down that that speed. the network runs at the speed of its slowest component.

paulc's avatar

Actually, I just got one of these airport extremes and when in N/G mode my N device gets significantly better speeds than the G devices but about a third or less of what it can get under N only mode. I didn’t do any real scientific tests, I just tested downloading a large file from the same place.

chrismeller's avatar

What @samkusnetz said. Connecting any non-N devices to the network will slow down the performance of N devices.

brilthor's avatar

the n based devices will only slow down when the g-based devices are in the process of transmitting or receiving.

a wireless router, be it n, g, b, or a in a certain instant in time can only be receiving or transmitting from a single client. During these instances the router is communicating with the client at the speed and coding that creates the best throughput for that situation. So when communicating with a g-based device at close range it may be running at the peak 54mbps in that instant in time. At a later instant in time when communicating with an n-based device it will communicate at the optimum rate and coding for that situation.

this is what occurs in most wireless routers (those that are properly designed)

there are a couple optional improvements with the n-based infrastructure that may be disabled when in compatibility mode: these are foremost the broader spectrum (going across 40mhz instead of 20mhz) as well as the option of using a shorter guard interval that were not included in previous standards.

the slowdown that people might be referencing here is that when a g-based device is connected to the network that device will take more time (a greater number of those previously mentioned instants) to transfer the same amount of data, and since only one client can either be transmitting or receiving during each of those instants it means that there are fewer such instants available for transmitting data to and from the n-based device meaning a lower perceived throughput.

in short the mere act of connecting the backwards compatible device does not inherently slow down the n-based network, but it will use more time when it is transmitting and receiving data leaving the n-based device with less time (which also would happen when connecting a second n-based device, just not to the same extent)

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