I thought wireless n is backwards compatible with g and b (and wireless g is backwards compatible with b)? If this is so, why do many home routers have settings to specify "wireless n only"? I have heard using wireless n only is faster than allowing a mix of b/g/n is this true? Is it more reliable too?
An example of one I'm talking about is the Hitron.
Yes, 802.11n-only (also known as greenfield mode) will operate much faster than mixed-mode 802.11b/g/n. When in greenfield mode, the devices will all operate at the higher rates of 802.11n without any errors or backoffs. In mixed-mode 802.11b/g/n, your 802.11n community of devices will be running in greenfield mode, until an 802.11b or an 802.11g packets is heard by your AP or devices. In that case, since 802.11b and 802.11g traffic runs at a slower rate, it will need more air-time to transmit. In order for the slower stations to get their packets through, they send an IE (Information Element) in their packets telling the AP and devices to hold their transmission for the duration of the timeout, so that the 802.11b and 802.11g devices have a chance to transmit. As you can see, this will affect the performance of 802.11n by throttling its transmission to allow for slower traffic to get their chance at transmitting packets. As far as more reliable, in a sense yes - Running in greenfield mode will allow for less errors and collision of packets, but we all know that TCP is resilient and will retry.
N-only (greenfield mode) is only faster when your radio environment is like a "green field". That is, when there are no G or B devices in radio range of your network, and when your devices are close enough to the AP to use N rates.
N rates use modulation and coding schemes that are too complex to decode reliably at low signal levels, so even N clients fall back to G or B at range when needed, if the AP allows those rates. So disabling G and B shrinks the usable range of your network, and doesn't help much unless you live out in the countryside without any neighbors with old equipment.
Newest WiFi have many modes(a,b,g,n,ac) or standard and only one mode at a time will be used.
For example:
Suppose you set the router to mix modes (support b,g,n) and your device (support b,g,n) it will automatically use the highest mode that is n.
And while your device connected, other device (support b,g) trying to connect to your router, the router will changing the mode to g.
And there is other device (support b only) trying to connect then the mode will change to b.
That is why many user want to lock the mode to "n only" just to make sure they have the fastest mode. There are other advanced technique to boost the speed by combining the frequencies not the modes.
cheers.
