What is the spread spectrum communication technology _ advantages and disadvantages of spread spectrum communication technology
What is spread spectrum communication technology? Spread Spectrum Communication (Spread Spectrum CommunicaTIon) is abbreviated as spread spectrum communication, which is characterized by the bandwidth used to transmit information is much larger than the bandwidth of the information itself. Spread spectrum communication technology uses spread spectrum coding for spread spectrum modulation at the origin, and receives information at the receiving end with relevant demodulation technology. This process has many excellent features. Spread spectrum communication technology is a kind of information transmission mode, and the bandwidth occupied by the signal is much larger than the minimum bandwidth necessary for the transmitted information; the expansion of the frequency band is completed by an independent code sequence, which is realized by the method of coding and modulation. It has nothing to do with the transmitted information data; at the receiving end, the same code is used for synchronous reception, despreading and restoring the transmitted information data.
The spread spectrum communication technology performs spread spectrum modulation at the transmitting end with spread spectrum coding, and receives the signal at the receiving end with the relevant demodulation technology. Since spread spectrum communication is spread spectrum modulated transmission using spread spectrum coding, and signal reception needs to be obtained by correlation despreading between the same spread spectrum codes, this provides a basis for frequency multiplexing and multiple access communication. Fully utilizing the correlation characteristics between the spreading codes of different patterns and assigning different spreading codes to different users, the signals of different users can be distinguished, and the frequency multiplexing can be realized without interference from other users.
Spread spectrum communication technology is an information processing transmission technology. Spread spectrum communication technology is a technique of spreading a signal to a plurality of carrier frequencies by using a code that is independent of the transmission data (information) in the same domain. Make it take up far less than the minimum bandwidth necessary to transmit information. Spread spectrum communication technology can provide more secure transmission, and can reduce interference and improve frequency band utilization. The spread spectrum technology is used to add the jitter processing to the clock frequency, so that the transmission frequency is no longer concentrated at one frequency point, and the electromagnetic interference can also be reduced.
There are three main methods for commonly used spread spectrum techniques, namely direct sequence spread spectrum, frequency hopping spread spectrum, time hopping spread spectrum, and linear modulation . However, in the process of actual use, their mixing is often used.
Spread spectrum communication technology features
The spread spectrum communication system has the following two characteristics:
(1) The bandwidth of the transmitted signal is much larger than the bandwidth of the original information signal being transmitted;
(2) The bandwidth of the transmitted signal is mainly determined by the spreading function, which is usually a pseudo-random (pseudo-noise) encoded signal.
The above two features are sometimes referred to as criteria for judging a spread spectrum communication system.
The biggest feature of the spread spectrum communication system is its strong anti-human interference, anti-narrowband interference and multi-path interference resistance.
Advantages and disadvantages of spread spectrum communication technology
Communication systems using spread spectrum technology have the following advantages:
(1) Good anti-interference performance, it has strong anti-human broadband interference, narrow-band aiming interference, relay-and-forward interference, and is beneficial to electronic opposition. If adaptive cancellation, adaptive antenna, and adaptive filtering are used, multipath interference can be eliminated, which is advantageous for military and civilian mobile communications.
(2) The concealment is strong and the interference is small. Since the signal is spread over a wide frequency band, the power per unit bandwidth is small, that is, the signal power spectral density is very low. The signal is submerged in white noise, it is difficult to find the existence of the signal, and with the spread spectrum coding, it is more difficult to pick up the useful signal. Spread spectrum communication technology broadens the bandwidth of the transmitted signal, thereby reducing the "flux density" of the system in the unit bandwidth, which is good for space communication.
(3) It is easy to implement code division multiple access, and spread spectrum communication occupies broadband spectrum resources, improves anti-interference ability, and improves frequency band utilization.
Disadvantages of the spread spectrum system:
(1) The frequency bandwidth used by the system.
(2) Compared with FDMA and TDMA multiple access methods, the CDMA multiple access method using spread spectrum technology is more complicated in mobile communication systems.
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