What does cdma mean?

CDMA generally refers to code division multiple access, and code division multiple access refers to multiple access communication realized by using the correlation of code sequences.

The basic idea of Code Division Multiple Access (CDMA) is to distinguish addresses by different address codes. Each is equipped with a different address code, and the carrier (the same carrier) sent by users is modulated by both baseband digital signals and address codes. When receiving, only the receiver who knows its assigned address code can demodulate the corresponding baseband signal, while other receivers cannot demodulate the signal because of different address codes.

This division is realized and recognized according to different code structures. Generally, pseudo-random code (PN code) is selected as the address code. Because the symbol width of PN code is much smaller than that of PCM signal (usually an integer multiple), the spectrum of the signal with pseudo-random code is much larger than that of the original baseband signal, so code division multiple access is also called spread spectrum multiple access.

Extended data

Code division multiple access (CDMA) communication

Code division multiple access system assigns each user a multiple access code. In order to accurately identify and extract useful information, it is required that the autocorrelation characteristics of these codes are sharp and the peak value of cross-correlation characteristics is as small as possible. At the same time, the interference between users can be minimized. [9]?

Code division multiple access system has the following characteristics:

(1) All users can enjoy the resources of the whole frequency band asynchronously, that is to say, the time when different user symbols send signals does not need to be synchronized;

② Large system capacity;

③ The channel data rate is very high.

Baidu encyclopedia -CDMA