title: create collision in wireless m2m network and simulate the packet dropping in omnett++
body: <p>scenario :i need to simulate a collision within a m2m network with one server, 2 gateways and each gateway having 5 node hierarchically connected. the simulation should show the packet being dropped when packet from nodes through gateway arrive at server at same time and analyse the dropped packet for delay and reliability. </p>
  
  <p>question :
   1.how do i simultaneously sent the packet from gateway to server at same time?
  2.how do show in simulation the packet being dropped?
  3.how to show the collision happened inside the server ?</p>