802.11n

[Silver-0-surfer]

Hey

can someone please explain what the deal with 11n is?

As far as I understand it works in the 2.4ghz & 5ghz spectrum, is that correct? also I was told that it bonds 3 channels to give higher thoughput, does that mean that if you use it in the 2.4ghz spectrum that you only get 1 clean channel? or am i completely lost?

 

[blaaislaai]

its 300mbps

 

[Silver-0-surfer]

its 300mbps

ok...

did you read my post?

 

[Roman4604]

As far as I understand it works in the 2.4ghz & 5ghz spectrum, is that correct? also I was told that it bonds 3 channels to give higher thoughput, does that mean that if you use it in the 2.4ghz spectrum that you only get 1 clean channel? or am i completely lost?

Not 100% sure myself, I can only go by observation.

My laptop's Intel 5100ABGN adapter allows one to select 2.4 & 5.2 channel widths (20MHz only or Auto), so I assume it is able to operate/aggregate in both bands.

My AP (TP-Link TL-WA901ND) is advertised at being 300Mbps capable, however its seems to only utilise 2.4 since there is absolutely no reference to anything in the 5GHz band (e.g channel selection etc.).

With the AP in 802.11 bgn mixed mode (to also support non-N devices) and channel width set to 40MHz, I'm able to eek out a real-world max throughput of just under 11MB/s (~85Mb/s) in Win to Win file copying (laptop on wireless N, desktop on GbE).

So nowehere near the advertised 300Mbps but still way better than 802.11g's real-world max of up to 24Mbps for WLAN application.

 

[blaaislaai]

ok...

did you read my post?

yes, I few times.. ?

With some googling you could have gotten the info you wanted:

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

 

[Roman4604]

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

I think from a practical perspective what 802.11n can do is largely up to vendor implementation of the spec (as per my observations above) ...

Deployment strategies

To achieve maximum output a pure 802.11n 5 GHz network is recommended. .... This setup assumes that all the 802.11n clients are 5 GHz capable, which isn't a requirement of the standard.

 

[Silver-0-surfer]

The question I have is not really about through put and how fast it is. The question is, It must be in both frequency's because my laptop is b/g/n and does not connect to an 802.11a AP and on my work laptop I can also select a/n or b/g/n. So I assume that it works in both spectrum's. The REAL question though is this, does it just use 1 channel, like a/b/g/n (I realize that the channels overlap, however you still select the channel you would like to work on) or does it use more than one channel?

 

[Roman4604]

It must be in both frequency's because my laptop is b/g/n and does not connect to an 802.11a AP and on my work laptop I can also select a/n or b/g/n.

Dont know how you come to that conclusion? Whether you can connect to an AP on' a' or 'n' is a function of whether that AP supports those protocols/frequencies, and 'a' != 'n'.

The REAL question though is this, does it just use 1 channel, like a/b/g/n (I realize that the channels overlap, however you still select the channel you would like to work on) or does it use more than one channel?

Most definately, even 802.11g uses 3 channels, the one you select is merely the center channel.

What I'm unsure of is how many channels can/will 802.11n actually use (in 2.4 and/or 5.X). From what I can see this is a function of vendor implementation as the spec seems to allow for some implementation variance.

 

[Silver-0-surfer]

Dont know how you come to that conclusion? Whether you can connect to an AP on' a' or 'n' is a function of whether that AP supports those protocols/frequencies, and 'a' != 'n'.

right, but the wifi card on the client needs to support that as well. So what I am saying is, a wifi card that can do b/g/n can connect to .11n IF it is broadcasting in the 2.4ghz spectrum, if it is broadcasting in 5ghz it would not be able to connect otherwise it would also be able to connect to .11a which is in the 5ghz

 

[Roman4604]

if it is broadcasting in 5ghz it would not be able to connect otherwise it would also be able to connect to .11a which is in the 5ghz

Cant say I'm following you completely, but I dont think you can infer whether an AP/card supports 5GHz on 'n' based on its support of 'a' ?

EDIT: That said, I have found some correlation between 'a' & 'n' @ 5GHz with D-Links new products.

DIR-655 - bgn, assume 'n' only @ 2.4
DIR-855 - abgn, stated support for 'n' @ 2.4 & 5.x concurrently.

So seems simulateous support/aggregation of 2.4 + 5.x channels is a vendor/chipset manf. implementation choice. Still doesnt answer how many channels can 'n' use? Or whether 2.4 +5.x can provide > 300Mbps (raw/marketing speeds of course) by aggregating even more channels, or is it merely a case of substituting less busy 5.X channels for congested 2.4 ones?

 

[Roman4604]

Out of interest did some more fishing around to see what 802.11n practically delivers from some of the major consumer/soho vendors. The variance is quite large ...

802.11n (Lite) @ 2.4GHz only - claim up to 150Mbps raw speed, do not claim compliance (subset of spec), e.g. TP-Link TL-WA701ND, Belkin N150
802.11n @ 2.4GHz only - claim up to 300Mbps raw speed, claim draft/draft2.0 compliance, e.g. TL-WA901ND, D-Link DIR-655, Linksys E1000
802.11n @ 2.4GHz or 5.xGHz selectable - claim up to 300Mbps raw speed, claim draft/draft2.0 compliance, e.g. Linksys E2000
802.11n @ 2.4GHz and 5.xGHz concurrent - claim up to 300Mbps raw speed, claim draft/draft2.0 compliance, e.g. D-Link DIR 855, Linksys E3000
802.11n @ 5.xGHz only - not really prevelant in the WLAN space, more for long-range application, e.g. Mikrotik R5nH, Ubiquiti Rocket M5

Interesting to note no one claims > 300Mbps raw wireless performance. Therefore it would be safe to assume 2.4 + 5x dual-band support is more about maintaining a robust signal than speed i.e. more channels to select from in the two band to avoid noise.

The overriding thing to take from this is, unlike the previous 802.11g standard where all implementations we near identical, currently in the 802.11n world things are not as clear cut. One must drill a little deeper to understand what capabilites you're actually getting from a device supporting 802.11n.