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I am simulating a dense network in NS-3, with around 200 nodes each sending 1MB of data to a single AP/router. Although I have set the CCA threshold to a very low value (so that all 201 nodes are within each others' range, implying that hidden/exposed terminal problems don't occur), I can see that packet loss still occurs (data is not received from all the 200 nodes).

What could be the primary reason for this packet loss? Could collisions still occur in this scenario? One reason could be that 2 nodes stumble upon the same back-off counter, which leads to them transmitting at the same time. Are there any other reasons for collision or any other kind of packet loss?

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  • \$\begingroup\$ Isn't answering these question exactly why you use NS-3? Also, have you considered thermal noise, even if there's no interference? \$\endgroup\$
    – Marcus Müller
    Jun 9, 2017 at 21:25
  • \$\begingroup\$ Yes I came to this site to find out what exactly I should look for. NS-3 will then allow me to investigate along those lines. However, at this point, it is difficult for me to say what really is causing the packet loss. The thermal noise is not very high; The resultant SNR at all nodes is good (>=5dB). \$\endgroup\$
    – V-Red
    Jun 9, 2017 at 21:28
  • \$\begingroup\$ Any noise will inherently lead to flipped bits. Enough flipped bits are a broken packet. Nothing surprising here. What did you expect with non-zero noise power? \$\endgroup\$
    – Marcus Müller
    Jun 9, 2017 at 21:53

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