Difference between digital walkie-talkie and analog walkie-talkie

In the digital walkie-talkie, the analog voice signal is first converted into a digital signal through A/D conversion and voice coding. Because the bandwidth of the digital walkie-talkie is relatively narrow, generally 12.5kHz or 6.25kHz, (analog is 12.5kHz or 25kHz), the speech coding in the digital walkie-talkie generally adopts the parametric coding method, that is, the waveform of the voice signal is not encoded, but Extract the characteristic parameters of the generated voice signal and encode and transmit the characteristic parameters. The transmission rate is generally 1.2~4.8kb/s, which can meet the bandwidth requirements of digital walkie-talkies.

The main purpose of channel coding and decoding is to improve the reliability of the digital transmission system. By adding some redundant symbols to the output sequence of speech coding according to certain rules as supervision codes for error control, the receiving end can find errors or errors according to this rule. Automatically correct errors to achieve.

Analog walkie-talkies generally use methods such as frequency scramble to encrypt information, which is simple and easy to crack. Digital walkie-talkies use digital encryption to protect user information, which is more competitive in some special industries such as civil aviation, railways and other industries that require high information security. There are many encryption methods. For example, the digital signal can be added modulo 2 to a m sequence with a long period to complete the encryption. The receiving end uses the same m sequence and the received encrypted signal to perform modulo 2 addition again, that is, the decryption is completed. .

Compared with analog walkie-talkies, digital walkie-talkies have the characteristics of strong anti-interference ability, good call quality, high frequency utilization, good confidentiality performance, support for data services, easy to carry out error-free relay, and easy to use a set of digital relay systems. The law of communication development, there is no doubt that digital walkie-talkies are the direction of the development of walkie-talkie technology, and will inevitably replace analog walkie-talkies gradually.