In legacy GSM network, we usually use GPRS( General Packet Radio System) and then EDGE(Enhanced Data Rates For GSM Evolution). EDGE is the one which provides the highest throughput 384Kb. But with the passage of time more applications are added in the global network like facebook,orkut and media applications like youtube and iptv which demands more bandwidth. But it's not possible to deliver these type of application in the existing GSM network. Parallel there is one more group which is working on CDMA2000 which is able to deliver the bandwidth more than GSM network. But the main problem with CDMA is that no roaming functionality is available.
To increase the throughout and higher data transfer rates for mobile subscriber, Wimax(Worldwide Interoperability for Microwave Access) is the upcoming standard which is being adopted by most of the service providers. The advantage of using Wimax is that no intellectual property rights. Any vendor can use anything according to the standards listed as in Wimax forum. Wimax falls in 4G category which is fully based on packet switched core(IP Core), no more circuit switching. Wimax works on 802.16d(Stationed) and 802.14e(Roaming) standards. Current Wimax revision provides upto 40 Mbps of speed which is almost equivalent to DS3. Wimax is using OFDM(Orthogonal Frequency Division Multiplexing). Wimax is last mile technology and it could be implemented on existing infrastructure.
Reasons for Wimax not GSM or CDMA:-
1. Intellectual Property Rights (IPR) problems with 3G (Qualcomm).
2. Large ecosystem is developing including handset vendors
3. Will go all-IP End to End years ahead of 3G.
4. “open” systems.
5. Fit with the existing infrastructure.
6. Higher ARPU(Average Revenue Per User).