CDMA network layers make digital calls to each other and assign unique codes to distinguish them. Each call data is encoded with a different key, and then these calls are transmitted at the same time.
GSM stands for global mobile communication system, and is now regarded as the standard of global communication, especially in Asia and Europe, and it is available in more than 265,438+00 countries all over the world.
GSM has four different frequency bands, 900 MHz and 1800 MHz in Europe and Asia, and 850 MHz and 1900 MHz in North America and South America.
The history of the development of mobile phone form;
1. 1 g The first generation of mobile phones (1G) refers to analog mobile phones, which appeared in works such as China, Hongkong and the United States in the 1980s and 1990s. The first person to develop a mobile phone was Dr. Cooper from Motorola, USA.
2.2G The second generation mobile phone (2G) is also the most common mobile phone. Usually, these mobile phones use very mature standards such as PHS, GSM or CDMA, with stable call quality and appropriate standby time.
3.3G .3G, the abbreviation of English 3rdGeneration, refers to the third generation mobile communication technology. Compared with the first generation of analog mobile phones (1G) and the second generation of GSM, CDMA and other digital mobile phones (2G).