3G, whose full name is 3rd Generation, means third-generation digital communications in Chinese. 　　 The first generation of analog mobile phones (1G), which came out in 1995, can only make voice calls; the second generation of digital mobile phones (2G) such as GSM and TDMA, which appeared in 1996 and 1997, added the function of receiving data, such as receiving emails or web pages; 3G was not born in 2009, it is a product of the last century, and 4G was already produced abroad as early as 2007 China also successfully developed China 4G in 2008, whose network transmission speed can reach 2G per second, which is equivalent to the next movie taking only one second. In Japanese and Korean films such as "My Sassy Girl" in the late 1990s, the video phone used by the heroine that allows the other party to see her is one of the important applications of 3G technology. The use of 3G in countries such as Japan and South Korea was a matter of late last century. At present, some regions abroad have already started trial operation of 3.5G or even 4G networks. 　 (The following is misleading) The main difference between the third generation (3G), which came out in 2009, and the previous two generations is the increase in the speed of transmitting sound and data. It can better achieve seamless roaming around the world and process multiple media forms such as images, music, and video streaming. It provides a variety of information services including web browsing, conference calls, and e-commerce At the same time, good compatibility with existing second-generation systems must also be considered. To provide this service, wireless networks must be able to support different data transmission speeds, that is, transmission speeds of at least 2Mbps (megabits/second), 384kbps (kilobits/second), and 144kbps in indoor, outdoor, and vehicular environments, respectively. ( This value changes depending on the network environment). 　　 3G standards. The International Telecommunication Union (ITU) has currently identified four major 3G standards in the world, namely WCDMA, CDMA2000, TD-SCDMA and WiMAX. 3G Standards In May 2000, the International Telecommunication Union (ITU) determined four major wireless interface standards: W-CDMA, CDMA2000, TD-SCDMA and WiMAX, and included them in the 3G technical guidance document "International Mobile Telecommunications Plan 2000" (IMT—2000). CDMA, short for Code Division Multiple Access (Code Division Multiple Access), is the technical foundation of third-generation mobile communication systems. The first generation of mobile communication systems used analog modulation of frequency division multiple access (FDMA). The main disadvantages of this system are low spectrum utilization and signaling interference with voice services. The second generation mobile communication system mainly adopts the digital modulation method of time division multiple access (TDMA), which improves the system capacity, and adopts independent channel transmission signaling, which greatly improves the system performance. However, the system capacity of TDMA is still limited and the cross-zone switching performance is still imperfect. CDMA systems show great development potential with their simple frequency planning, large system capacity, high frequency multiplexing coefficient, strong multipath resistance, good communication quality, soft capacity, and soft switching. The following introduces several 3G standards: (1) W-CDMA is also called WCDMA, full name Wideband CDMA, also known as CDMA Direct Spread, meaning broadband division multiple access. This is a 3G technical specification developed based on GSM network. It is a broadband CDMA technology proposed by Europe. It is basically the same as the broadband CDMA technology proposed by Japan and is currently being further integrated. W-CDMA's supporters are mainly European manufacturers mainly based on GSM systems, and Japanese companies are also more or less involved, including Ericsson, Alcatel, Nokia, Lucent, Nortel in Europe and the United States, as well as NTT, Fujitsu, Sharp and other Japanese manufacturers. This standard proposes an evolution strategy of GSM(2G)-GPRS-EDGE-WCDMA(3G). This system can be installed on the existing GSM network, which can be easily transitioned for system providers. However, the acceptance of this new technology in Asia, where GSM systems are quite popular, is expected to be quite high. Therefore, W-CDMA has an innate market advantage. 　　 (2) CDMA2000 CDMA2000 is a broadband CDMA technology developed from narrowband CDMA (CDMA IS95) technology, also known as CDMA Multi-Carrier. It was proposed by Qualcomm North America, USA, with the participation of Motorola, Lucent and later Samsung of South Korea. South Korea has now become the leader of the standard. This system is derived from the narrow-frequency CDMAOne digital standard and can be directly upgraded from the original CDMAOne structure to 3G with low construction cost. However, the only regions currently using CDMA are Japan, South Korea and North America, so CDMA2000 does not have as many supporters as W-CDMA. However, the research and development technology of CDMA2000 is the fastest among all standards at present, and many 3G mobile phones have been launched first. The standard proposes an evolution strategy from CDMA IS95(2G)-CDMA20001x-CDMA20003x(3G). CDMA20001x is called the 2.5th generation mobile communication technology. The main difference between CDMA20003x and CDMA20001x is the application of multi-carrier technology, which improves bandwidth by adopting three carriers. China Telecom is currently using this solution to transition to 3G and has built the CDMA IS95 network. 　　 (3) TD-SCDMA, whose full name is Time Division - Synchronous CDMA (Time Division Synchronous CDMA), is a 3G standard independently developed by mainland China. It was proposed to ITU by the Telecommunications Science and Technology Research Institute (Datang Telecom) of the former Ministry of Posts and Telecommunications of China on June 29, 1999. The standard integrates today's leading international technologies such as smart wireless, synchronous CDMA and software wireless, and has unique advantages in spectrum utilization, flexibility for business support, frequency flexibility and cost. In addition, due to the huge market in China, this standard has been valued by major telecommunications equipment manufacturers, and more than half of the world's equipment manufacturers have announced that they can support the TD—SCDMA standard. This standard proposes to transition directly to 3G without going through the intermediate link of 2.5 generations, and is very suitable for upgrading GSM systems to 3G. 　　 (4) WiMAX WiMAX, whose full name is Worldwide Interoperability for Microwave Access (WIA), also known as 802·16 Wireless Metropolitan Area Network, is another broadband wireless connection solution that provides “last mile” broadband wireless connectivity for business and home users. Combining this technology with microwave equipment that requires authorization or no authorization will expand the broadband wireless market and improve the awareness of enterprises and service providers due to its lower cost. On October 19, 2007, at the Wireless Communications Plenary Meeting held by the International Telecommunication Union in Geneva, after a majority of countries voted to approve it, WiMAX was officially approved as the fourth global 3G standard after WCDMA, CDMA2000 and TD-SCDMA.