in old days there was only one way of communication,that was letter.they wrote a letter and send it do their destinations by different ways.if they wanted that their letter reach in one day with in that country,then they had to pay more money and their letter had given to that passenger vain which was going first.and if they wanted to send letter to abroad then this process would done by Aeroplane.this way take too much time to respond

then people thought to improve communication way and then they made telephone, a wired communication..initially this was unidirectional like walkie talkie.then bidirectional communication started.with telephone we can touch with people with in a minute by just dialing his phone number.and if some one want to call to another country, first he had to ask his country main center of telephone to connect with that no with which he wanted to connect.

then people think that there should be no interference of other when we want to call any where in the world and secondly communication system should b wireless. so they mad mobile.which was a great evalution in telecom field.now we don't need to ask some one to connect our call to abroad..and secondly our calling device is in our pocket.

FIRST GENERATION 

in the early stage in mobile we only have GSM technology, mean mobile are used just for calling.this is called 1G(first generation)

SECOND GENERATION

in second generation packet data delivery is used for internet.this was first time where information was send in the form of packets.data rate was 64kbps.and it is called GPRS.this period is called 2G(second generation)

THIRD GENERATION

in the period of second generation when user increased then thin this data rate was not enough for those user that's why telecom engineer starts to think about it's solution.then they increase data rate up to 2 mbps..this is called as 3G. this is technique which is used in many countries now a days.

FOURTH GENERATION

this technology also used in many countries.in this technology data rate is too high.its data rate is like if a person want to download some file.in 3G if it is 1% then in 4G it will b complete.