Why 802.11b devices afftecting all the other devices operating 802.11g/n

[susim]

Hi all 

Why 802.11b devices afftecting  throughput of  all the other devices operating   802.11g/n 

Thanks 

[Leo Laohoo]

It's not just 802.11b but affects all, including 802.11a. 

This is because wireless medium is one big collision domain or behaves like a wireless HUB:  When one talks, everyone else stops talking, listens for their turn to talk.  

[MeMySelfundCisco]

"b" is the "slow" cousin of 2.4 Ghz. It also is the oldest used wireless protocol. the Cycles B uses to transmit are basically just longer. So it is hogging airtime, and thus slowing down other clients, that might be able to go faster. If you don´t have older "B" devices, you could try to disable the rates up to 12mbit´s and you might be surprised! 

[Leo Laohoo]

you could try to disable the rates up to 12mbit´s and you might be surprised! 

You will be "surprised" all right if you disable 12 Mbps and you run wireless Voice.  When you disable 12 Mbps, your handsets will be able to associate to the network just fine but you won't be able to make any incoming and outgoing calls as CAC protocol uses 12 Mbps by default.  

"b" is the "slow" cousin of 2.4 Ghz

802.11b and 802.11g uses the same 2.4 Ghz spectrum.  While 802.11g is faster, 802.11b is the slowest.  

[susim]

Hi 

You mean to say that  in order to use wireless ip phones , do we need to depends B rates ?

[Leo Laohoo]

No, I didn't mean that.  

Wireless VoIP will depend entirely upon the manufacturer of your phones.  Personally, I've configured our 7921G/7925G to prefer 802.11a but use 802.11b when the signal (for 802.11a) is low.

[travisbugh]

The main reason is modulation type. DSSS is used for 802.11b while G/N uses OFDM. There is a lot of variables as to how much a B client affects a cell, but it most certainly takes the other 2.4 GHz in the cell and reduces their performance (compared to a cell containing only OFDM using clients).