Just an add on answer to the excellent inputs. GSM is based on TDMA – Time Slots associated with a frequency. To alleviate interference a RF frequency plan is set up by the CSPs. 3G is based on spread spectrum that uses a PRBS to spread information with the allotted bandwidth. 3G is a power / bandwith intensive solution. NodeB and eNodeB (4G) is used.
VBR/ Wallis Dudhnath