Why Up-link frequency is Higher than Down-link Frequency

The communication from transmitting earth station to satellite is called Uplink frequency . 

The communication link from  Satellite to Earth station is called Downlinks frequency

It is because a mobile is operated on a battery with low power and it sends  signals on low( up-link ) frequencies whereas a base station is driven by high power and can easily send signal on high frequencies . this can be defined by Friis equation  which say Transmitted power and Transmitted frequency are directly proportional .it is because a mobile phone operated with low power and therefore it send low uplink frequency 

Satellite is limited power Supply and operated by solar cell and batteries which can not support High power transmission 

Narrow Beam produced by Higher frequency and cover a larger area on Earth .it is using broad beam  by Low frequency .

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