Frequency hopping serves three major purpose in GSM

 

1) FREQUECY RESUSE AND TO AVOID CO-CHANNEL INTERFERENCE

2) INCREASES THE  CHANNEL CAPACITY OF LIMITED GSM CHANNELS

3) DECREASES MULTIPATH INTERFERENCE OF RADIO SIGNAL.

 

 

"  Frequency Hopping  rule is simple,  that our conversation must remain on the same physical channel and time slot for the entire time we are on a particular site. If the network were able to move us from slot to slot, and from frequency to frequency, then we could randomize the effects of interference "