TD-SCDMA is the abbreviation of English time division-synchronous code division multiple access (time division-synchronous code division multiple access). The third generation mobile communication standard (3G for short) proposed by China is also one of the three 3G standards approved by ITU. It is an international standard for wireless communication, which is based on intellectual property rights in China and widely accepted and recognized internationally. This is an important milestone in the telecom history of China. Compared with the other two main 3G standards, CDMA2000 and WCDMA, it started late and the technology is not mature enough. According to Nomura Securities, by the end of 20 14, the accumulated investment in TD-SCDMA network construction exceeded188 billion yuan. Coupled with the terminal subsidies and marketing resources invested by China Mobile, it is conservatively estimated that the investment far exceeds 200 billion yuan.

The Global System for Mobile Communications, known as GSM, is the most widely used mobile phone standard at present. More than 6,543.8 billion people in more than 200 countries and regions around the world are using GSM mobile phones. The ubiquity of GSM standard makes it common for users to roam internationally after signing a "roaming agreement" between mobile phone operators. The biggest difference between GSM and previous standards is that its signaling and voice channels are digital, so GSM is regarded as the second generation (2G) mobile phone system. This shows that digital communication has been established in the system for a long time. GSM is an open standard currently developed by 3GPP.

Code Division Multiple Access (CDMA) is a new and mature wireless communication technology developed on the basis of spread spectrum communication technology, a branch of digital technology. The principle of CDMA technology is based on spread spectrum technology, that is, the information data to be transmitted with a certain signal bandwidth is modulated by a high-speed pseudo-random code with a bandwidth much larger than the signal bandwidth, so that the bandwidth of the original data signal is expanded and then transmitted by carrier modulation. The receiver uses the same pseudo-random code to correlate with the received bandwidth signal, and changes the broadband signal into the narrowband signal of the original information data, that is, despreading, thus realizing information communication. CDMA refers to spread spectrum multiple access digital communication technology, which establishes a channel through a unique code sequence. This technology can be used in any protocol of the second and third generation wireless communication. CDMA is a multi-channel mode, and multi-channel signals only occupy one channel, which greatly improves the bandwidth utilization.