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In digital communications, chirp spread spectrum (CSS) is a spread spectrum technique that uses wideband linear frequency modulated chirp pulses to encode information. [1] A chirp is a sinusoidal signal whose frequency increases or decreases over time (often with a polynomial expression for the relationship between time and frequency).
Moreover, for a given noise power spectral density (PSD), spread-spectrum systems require the same amount of energy per bit before spreading as narrowband systems and therefore the same amount of power if the bitrate before spreading is the same, but since the signal power is spread over a large bandwidth, the signal PSD is much lower — often ...
A chirp is a signal in which the frequency increases (up-chirp) or decreases (down-chirp) with time. In some sources, the term chirp is used interchangeably with sweep signal. [1] It is commonly applied to sonar, radar, and laser systems, and to other applications, such as in spread-spectrum communications (see chirp spread spectrum). This ...
A simple way to derive the spectrum of a chirp using a computers, is to sample the time-domain waveform at a frequency well above the Nyquist limit and use an FFT algorithm to obtain the desired result. As this approach was not an option for the early designers, they resorted to analytic analysis, or and to graphical or approximation methods.
In the US, FCC part 15 on unlicensed spread spectrum systems in the 902–928 MHz and 2.4 GHz bands permits more power than is allowed for non-spread-spectrum systems. Both FHSS and direct-sequence spread-spectrum (DSSS) systems can transmit at 1 watt, a thousandfold increase from the 1 milliwatt limit on non-spread-spectrum systems.
Chirp spread spectrum (CSS) based devices. Sigfox, UNB-based technology and French company. [4] LoRa is a proprietary, chirp spread spectrum radio modulation technology for LPWAN used by LoRaWAN, Haystack Technologies, and Symphony Link. [5] [6] MIoTy, implementing Telegram Splitting technology.
software-defined radio and signal processing SDRangel: GPL: Windows, macOS, Linux: software-defined radio SDR# Freeware Windows software-defined radio receiver SDR++: GPL: Windows, macOS, Linux, Android: software-defined radio receiver WSJT: GPL: Windows, Unix, Unix-like: weak signal communication, modem for FT-8, FT-4, JT-65, and WSPR WSJT-Z ...
Direct-sequence spread-spectrum transmissions multiply the symbol sequence being transmitted with a spreading sequence that has a higher rate than the original message rate. Usually, sequences are chosen such that the resulting spectrum is spectrally white. Knowledge of the same sequence is used to reconstruct the original data at the receiving ...