[ns] How one 802.11 node recognizes other 802.11 node

[m w]

Hi All,
   
         Can anyone please tell me as to how 802.11b nodes recognize each other. My question is that when 802.11b nodes are increased then the throughput of the system degrades, so I was just wondering as to in which file (script) can I find this information where 802.11 nodes realize other 802.11 nodes in its vicinity. There should be some mechanism by which one node is aware of other node's presence. How is this implemented. It is a part of my project and am desperately looking for an answer. 
  Please Help !!!
   
  Thanks, 
  Manish

 		
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