The cellular networks are evolving through several generations.

The first generation (1G) wireless mobile communication network was analog system which was used for public voice service with the speed up to 2.4 kbps.

The second generation (2G) is based on digital technology and network infrastructure. As compared to the first generation, the second generation can support text messaging.

Its success and the growth of demand for online information via the internet prompted the development of cellular wireless system with improved data connectivity, which ultimately lead to the third generation systems (3 G).

3G systems refer to the developing technology standards for the next generation of mobile communications systems.

One of the main goals of the standardization efforts of 3G is to create a universal infrastructure that is able to support existing and future services. This requires that the infrastructure be designed so that it can evolve as technology changes, without compromising the existing services on the existing networks.

Separation of access technology, transport technology, service technology and user application from each other make this demanding requirement possible . The 4th Generation (4G) wireless mobile internet networks are research items in academy which will integrate current existing 3G cellular networks (i.e., OFDM, CDMA2000M, WCDMA AND TD-SCDMA) and Wi-Fi (i.e. Wireless LAN) networks with fixed internet to support wireless mobile internet as the same quality of service as fixed internet, which is an evolution not only to move beyond the limitations and problems of 3G, but also to enhance the quality of services, to increase the bandwidth and to reduce the cost of the resource.

The 5th wireless mobile multimedia internet networks can be completed wireless communication without limitation, which bring us perfect real world wireless - World Wide Wireless Web (WWWW).

5G is based on 4G technologies, which is to be revolution to 5G. During this processing, there are two kind of problems need to be solved. The first is wider coverage and the second is freedom of movement from one technology to another.

The 6th generation (6G) wireless mobile communication networks shall integrate satellites to get global coverage. The global coverage systems have been developed by four courtiers. The global position system (GPS) is developed by USA. The COMPASS system is developed by China.

The Galileo System is developed by EU, and the GLOANASS system is developed by Russia. These in depended systems are difficulty for space roaming. The task of 7th generation (7G) wireless mobile communication networks are going to unite the four systems to get space roaming. But we concentrate here only on 1G to 5G.