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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).
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 ).
The magnitude of this spectrum is shown in the attached figure, where these data points are samples in frequency. The data is cyclic so, in the plot, the zero frequency point is at n = 0 and also at n = 128 (i.e. both points are the same frequency). The point n = 64 corresponds to +fs/2 (and also to -fs/2). Spectrum of Linear Chirp, TB=25, N=128
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 ...
IEEE 802.15.4c was approved in 2008 and was published in January 2009. This defines a PHY amendment that adds new RF spectrum specifications to address the Chinese regulatory changes which have opened the 314-316 MHz, 430-434 MHz, and 779-787 MHz bands for Wireless PAN use within China.
ISO/IEC 24730-2:2012 Information technology — Real time locating systems (RTLS) — Part 2: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol ISO/IEC 24730-5:2010 Information technology — Real-time locating systems (RTLS) — Part 5: Chirp spread spectrum (CSS) at 2,4 GHz air interface
In August 2007, IEEE 802.15.4a was released expanding the four PHYs available in the earlier 2006 version to six, including one PHY using direct sequence ultra-wideband (UWB) and another using chirp spread spectrum (CSS). The UWB PHY is allocated frequencies in three ranges: below 1 GHz, between 3 and 5 GHz, and between 6 and 10 GHz.
This analysis drives the maintenance support for each repairable unit analyzed. LORA is the most important physical supportability analysis business decision made during acquisition of a system. [why?] LORA is performed in two steps (SAE Standard AS1390A): Establish noneconomic decision criteria used to make initial support decisions