effect of frequency : Up link Frequency Vs Down link Frequency

[muhammad11]

Q-1: Why up link frequency is different from down link frequency in GSM? why there is gap between up link and down link frequency?

Q-2 : What is effect of frequency(low or high frequency) on antenna height, and attenuation ?

Kindly explain these 2 questions in detail

 

[G4BCH]

Q-1: Why up link frequency is different from down link frequency in GSM? why there is gap between up link and down link frequency?
A 1
It is difficult to transmit and receive on the same frequency at the same time using a common antenna.
The hand set used TDMA on the uplink channel along with up to 7 other handsets. The base station transmits back to all handsets on the associated downlink.
There is a 45MHz difference between uplink and downlink channels so that the same local oscillator can be used for receive and transmit to convert to and from a 45MHz IF.

Q-2 : What is effect of frequency(low or high frequency) on antenna height, and attenuation ?
A 2 Don't understand what you are asking.

Try a Google search for GSM system description, base station operation description and or the same for handsets. There is plenty of GSM tutorial information out there if you look. If you want help with your home work then you will have to show that you have made at least some effort and ask for explanations on specific things saying where you are having difficulties, it will get a more sympathetic response.