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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, 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).
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 signal type is biologically inspired and occurs as a phenomenon due to dispersion (a non-linear ...
Subvocal recognition (SVR) is the process of taking subvocalization and converting the detected results to a digital output, aural or text-based. [1] A silent speech interface is a device that allows speech communication without using the sound made when people vocalize their speech sounds.
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Spread spectrum makes it possible to have as low a frequency reuse factor as 1, if each base station is divided into 3 cells by means of 3 directional sector antennas. This corresponds to a system spectrum efficiency of over 1 × 100 × 0.0017 = 0.17 (bit/s)/Hz per site , and 0.17/3 = 0.06 (bit/s)/Hz per cell or sector .
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 ...
Code-division multiplexing (CDM), code-division multiple access (CDMA) or spread spectrum is a class of techniques where several channels simultaneously share the same frequency spectrum, and this spectral bandwidth is much higher than the bit rate or symbol rate. One form is frequency hopping, another is direct sequence spread spectrum.