Before using the model, the user should select the values of the path loss exponent and the shadowing deviation according to the simulated environment.
The OTcl interface is still the node-config command. One way to use it is as follows, and the values for these parameters are just examples.
# first set values of shadowing model Propagation/Shadowing set pathlossExp_ 2.0 ;# path loss exponent Propagation/Shadowing set std_db_ 4.0 ;# shadowing deviation (dB) Propagation/Shadowing set dist0_ 1.0 ;# reference distance (m) Propagation/Shadowing set seed_ 0 ;# seed for RNG $ns_ node-config -propType Propagation/Shadowing
The shadowing model creates a random number generator (RNG) object. The RNG has three types of seeds: raw seed, pre-defined seed (a set of known good seeds) and the huristic seed (details in Section 25.1). The above API only uses the pre-defined seed. If a user want different seeding method, the following API can be used.
set prop [new Propagation/Shadowing] $prop set pathlossExp_ 2.0 $prop set std_db_ 4.0 $prop set dist0_ 1.0 $prop seed \<seed-type\> 0 ;# user can specify seeding method $ns_ node-config -propInstance $prop
The seed-type above can be raw, predef or heuristic.