Distribution spectrum (spread spectrum, SS)Spectrum is a communication technology that disperses the spectrum of transmitted signals to a wider bandwidth than original ones. It is often used in wireless communication. Strict definitions are divided into two parts:
- After the distribution spectrum is adjusted, the signal transmission bandwidth should be much larger than the original signal
- The transmission end uses a unique code, which is irrelevant to the transmitted data. The receiver must also use this unique code to deploy the spectrum to obtain the data of the transmission end.
Representative distribution spectrum methods include:
- Direct Sequence Distribution Spectrum(AbbreviationDirect distribution spectrum)(Direct-sequence spread spectrum, DSSS)
- Frequency Hopping (frequency-hopping spread spectrum, FHSS)
[Edit] development history
The distribution spectrum was originally used in military and intelligence systems. The main concept is to expand data signals into a wide spectrum, making it difficult to interfere with and Intercept Signals. Later, the technology was open and applied to areas such as CDMA (2G mobile communication) and WLAN (IEEE 802.11 series.
[Edit] advantages and uses
- It is immune to noise, interference, and multipath interference of the background.
- PairHuman deliberate interference (jamming)The signal has good defensive capabilities, which is one of the first important reasons why the distribution spectrum was used in military communication systems to combat human interference.
- Relatively good privacy, less likely to be intercepted in the communication process. This is because after the distribution spectrum, the power value per unit frequency is reduced, and it is difficult for the receiver to obtain information from the enemy through the spectrum analyzer. Even if the electric wave is received, because the receiver does not know the meaning of the distributed Spectrum Code, the encoding information cannot be returned. Therefore, distributed spectrum communication also has simple confidential communication capabilities.
- Electromagnetic interference reduction (EMI)
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If the clock generator of an electronic device is used to distribute the spectrum, that is, to add the jitter (jitter) to the clock signal ), in this way, the energy that may cause electromagnetic interference can be dispersed from a specific frequency to reduce the degree of interference, which is essentially the same as the distribution spectrum of communication technology.
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The Spread Spectrum option is often displayed in the BIOS settings of a personal computer. The main purpose of this option is to reduce electromagnetic interference, which may effectively reduce the amount of electromagnetic radiation based on different system configurations. However, the side effect is that the signal definition is reduced, which has a great impact on the system stability after overclocking.
- With the distributed spectrum technology, multi-division code (CDMA) communication can be achieved, allowing multiple users to use larger bandwidth independently at the same time.
