Even if I change the distance between nodes in a wlan network, it does not seem to affect my results in any way. How can I make the BER change when the distance between the nodes is changed?

Even if I change the distance between nodes in a wlan network, it does not seem to affect my results in any way. How can I make the BER change when the distance between the nodes is changed?

The OPNET WLAN model assumes that the distance between nodes is not more than 300 meters; this distance limitation is required by IEEE 802.11 specifications for the correct execution of the protocol.In the WLAN Suite, if two or more packetsoverlap in time even by one bit at a WLAN receiver, the packetsare considered as collided. This is a rare event because WLAN is acollision avoidance protocol. If a collision happens, the firstcollided packet is marked as bad but still accepted by the receiverregardless of how many bit errors it contains. Later, it is droppedby the WLAN MAC without processing. The other packets are marked as noiseat the pipeline stages; noise packets are ignored at the receiver. The bit error probablity is calculated in dra_snr as a function of the signal-to-noise ratio. Noise can be of two types: interference noise and background noise. However, as described above, for valid packets the interference noise is zero--there is also no interference from neighbor BSSs because they use different frequency bands. And, because the maximum distance between stations is only 300 meters, even the background noise would be insignificant compared to the signal power. So the BER would be practically zero if the distance between nodes is within the allowed range.To make the BER more significant, the signal power must be decreased and the noise power increased, so that the two are comparable. This can be done by modifying the pipeline stages used by the WLAN model. They are listed in the attributes of the radio transceivers in a WLAN node.

DES Kernel->Statistics and Reports,Protocols->Wireless LAN