Spread spectrum communication, together with optical fiber communication

Spread spectrum communication, together with optical fiber communication and satellite communication, is known as the three high-tech communication transmission methods entering the information age. Spread spectrum communication (SSC, Spread Spectrum Communication, spread spectrum communication technology), reduces the signal-to-noise ratio by increasing the signal bandwidth, and improves the anti-interference tolerance. mini bluetooth module The bandwidth of the signal used to transmit information is much larger than the bandwidth of the information itself. Compared with traditional narrowband communication, spread spectrum communication has many advantages: multiple access capability, low interception rate, strong anti-interference ability and high time resolution, etc., and is widely used in wireless communication. There are two representative spread spectrum methods: direct sequence spread spectrum and frequency hopping spread spectrum.

If the pseudo-random sequence code is directly added to the data, direct sequence spread spectrum (DSSS) can be obtained; if the pseudo-random code acts on the carrier frequency, frequency hopping spread spectrum (FHSS) can be obtained. It can also be combined to form DSSS + FHSS hybrid spread spectrum technology. 1. DSSS: Direct Sequence Spread Spectrum What is DSSS? ——Direct Sequence Spread Spectrum (DSSS, Direct Sequence Spread Spectrum) working method, referred to as direct spread method (DS method), is a widely used spread spectrum method at present. It is to use a high-speed spread spectrum sequence to spread the spectrum of the signal at the transmitting end, bluetooth low voltage transmitter module and use the same spreading code sequence to despread at the receiving end, and restore the expanded spread spectrum signal to the original signal. LoRa technology is a modulation method based on direct sequence spread spectrum. DSSS stands for Direct Sequence Spread Spectrum, and the information bits are modulated by a PN code (chip). The PN code is a pseudo-noise code symbol. This PN code has a short duration compared to the information bits. Here the information transmitted over the air takes up more bits of bandwidth than the user. DSSS is a modulation technique used in IEEE802.11-based WLAN compliant products. In a DSSS system, the entire system bandwidth is always available to each user.