Frequencies are allocated in such a way to save battery life (i.e. reduce transmitted power). As the path loss experienced for higher frequencies is higher (Path loss is proportional to frequency. This comes as higher frequencies – smaller wavelength – suffer more attenuation from different obstructions) the higher frequencies in a system are allocated to the side that has fewer power problems, i.e. the BTS to a mobile network or the earth station in a satellite network. This will ensure that the MS or the satellite will use the minimum possible power for communication.
>like u said lower frequency offer >less resistance , but why??? i >mean what r the factors???
the lower frequency, the wave lenght is higher. The more higher lenght becomes bigger compared to environmente things so it has less resistance in small things .