What is the big difference between 3G and 4G?

frequency, speed , bandwidth

When you answer a question, you should understand the one answering the question and what is his/her background!. She is a developer in Byte! not a telecommunication Engineer! besides, some of the answers above are wrong!

simply:

• on3G you can make calls and data, while on4G, you can only do data and VoIP.
• if you are on4G and you want to make a call, your phone will drop to3G, and go back to4G when you finish.
• 4G data speed supporse to be higher than3G, if you have a good network conditions (dominancy, less interference, enough codes ... etc)
• 3G data speed can go upto44Mbps (depending on the network certain configurations)
• 4G data speed can go upto100Mbps
• for your info away from your question,3G speed may exceed4G speed if not well optimized.
• theoretically, frequesncy is not related to the technology, any technology can be mounted on any frequency

difference in network point of view is their access method  to the Radio.

the way access technology is used to share the resources for user is different in both technology.

LTE is using OFDM, and3G is using WCDMA/CDMA

from the architectire point of view : LTE RAN has Flat architecture and only one N/W element in RAN while in WCDMA there are two N/W elements

also LTE is pure packet IP based n/w while in WCDMA IP and ATM boht can be used 

also there are many differences from the feature point of view like  in LTE we can have very high data speed, can use good services in high speed trian

better speed,better frequency,more better bandwidth.

3G require RNC & NodeB for access netwrok, while4G requires just eNodeB. this mean that4G requires less hardware and less complicated netwrok structure. In additon,4G gives much higher throughput comparing to3G.

Multiplexing

access 

modulation 

speed 

carrier BW 

Salam alaikum .....
The main difference between3G and4G is speed.4G speeds can be up to10 times faster than3G, similar to the speed difference between DSL and high-speed cable modem.
Average download speed on a3G network is between600 Kbps and1.4 Mbps with peak download speed of up to3.1 Mbps.
On a4G network the average download speed is3-6 Mbps with peak download speed of more than10 Mbps.
This speed difference is significant enough for people to completely abandon3G mobile broadband as soon as there is sufficient4G network coverage.
Another significant advantage of4G over3G is QoS support.
QoS (Quality of Service) , is a technology that is used by land-based data networks.
Basically, QoS makes it possible to vary priority levels for different data streams.
For example, VoIP is usually given the highest priority to ensure flawless connection quality.
Same with watching online HD videos – they usually get higher priority than other data.
The implementation of QoS in4G networks will enable people to use VoIP applications, such as Skype, on their mobile phones without any loss of quality.
It will also enable users to watch high quality online videos straight from their mobile devices.

more power more spreed also i do believe people need to run because its not time for walk

The main difference in network point of view is their access method ,

LTE is using OFDM, and3G is using WCDMA/CDMA .