18.4 Communication range

In some applications, a user may want to specify the communication range of wireless nodes. This can be done by set an appropriate value of the receiving threshold in the network interface, ,

Phy/WirelessPhy set RXThresh_ \<value\>

A separate C program is provided at ~ns/indep-utils/propagation/threshold.cc to compute the receiving threshold. It can be used for all the propagation models discussed in this chapter. Assume you have compiled it and get the excutable named as threshold. You can use it to compute the threshold as follows

threshold -m \<propagation-model\> [other-options] distance

where propagation-model is either FreeSpace, TwoRayGround or Shadowing, and the distance is the communication range in meter.

[other-options] are used to specify parameters other than their default values. For the shadowing model there is a necessary parameter, -r receive-rate, which specifies the rate of correct reception at the distance. Because the communication range in the shadowing model is not an ideal circle, an inverse Q-function [29] is used to calculate the receiving threshold. For example, if you want 95% of packets can be correctly received at the distance of 50m, you can compute the threshold by

threshold -m Shadowing -r 0.95 50

Other available values of [other-options] are shown below

-pl \<path-loss-exponent\> -std \<shadowing-deviation\> -Pt \<transmit-power\>
-fr \<frequency\> -Gt \<transmit-antenna-gain\> -Gr \<receive-antenna-gain\>
-L \<system-loss\> -ht \<transmit-antenna-height\> -hr \<receive-antenna-height\>
-d0 \<reference-distance\>

Tom Henderson 2011-11-05