Deciphering the History of Development and Change of Mobile Communication Technology What is communication? (2)

2G mainstream network standards:

GSM:

The Global System for Mobile Communication, known as GSM, is the most widely used mobile phone standard. More than 1 billion people in more than 200 countries and regions around the world are using GSM phones. The ubiquity of the GSM standard has made it common for users to roam internationally after "roaming agreements" are signed between mobile phone operators.

The biggest difference between GSM and its predecessor is that its signaling and voice channels are digital, so GSM is considered a second generation (2G) mobile phone system. This shows that digital communication has been built into the system from a very early time, and GSM is an open standard currently developed by 3GPP.

TDMA:

Time Division Multiple Access (TDMA) divides time into periodic frames, and each frame is further divided into several time slots to send signals to the base station. Under the conditions of timing and synchronization, the base station can receive the signals of each mobile terminal in each time slot without mixing. At the same time, the signals sent by the base station to a plurality of mobile terminals are arranged to be transmitted in a predetermined time slot in sequence. As long as each mobile terminal receives in the designated time slot, it can distinguish and receive the signal sent to it in the combined signal.

CDMA:

Code Division Multiple Access (CDMA) is a new and mature wireless communication technology developed on the branch of digital technology-spread spectrum communication technology. The principle of CDMA technology is based on spread spectrum technology, that is, the information data with a certain signal bandwidth to be transmitted is modulated with a high-speed pseudo-random code whose bandwidth is much larger than the signal bandwidth, so that the bandwidth of the original data signal is expanded. It is then modulated by the carrier and sent out. The receiving end uses the exact same pseudo-random code to perform correlation processing with the received wideband signal and replaces the wideband signal with the narrowband signal of the original information data, that is, dispreading, so as to realize information communication.