Search results
Results from the WOW.Com Content Network
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 ...
In digital communications, a chip is a pulse of a direct-sequence spread spectrum (DSSS) code, such as a pseudo-random noise (PN) code sequence used in direct-sequence code-division multiple access (CDMA) channel access techniques.
DASH7, a low latency, bi-directional firmware standard that operates over multiple LPWAN radio technologies including LoRa. Wize is an open and royalty-free standard for LPWAN derived from the European Standard Wireless Mbus. [3] Chirp spread spectrum (CSS) based devices. Sigfox, UNB-based technology and French company. [4]
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.
The IEEE 802.15.3 Task Group 3c (TG3c) was formed in March 2005. This mmWave WPAN is defined to operate in the 57–66 GHz range. Depending on the geographical region, anywhere from 2 to 9 GHz of bandwidth is available (for example, 57–64 GHz is available as unlicensed band defined by FCC 47 CFR 15.255 in North America).