In a spread spectrum system, the process gain (or 'processing gain') is the ratio of the spread (or RF) bandwidth to the unspread (or baseband) bandwidth. It is usually expressed in decibels (dB).
For example, if a 1 kHz signal is spread to 100 kHz, the process gain expressed as a numerical ratio would be 100,000/1,000 = 100. Or in decibels, 10log10(100) = 20 dB.
Note that process gain does not reduce the effects of wideband thermal noise. It can be shown that a direct sequence spread spectrum (DSSS) system has exactly the same bit error behavior as a non-spread spectrum system with the same modulation format. Thus, on an additive white Gaussian noise (AWGN) channel without interference, a spread system requires the same transmitter power as an unspread system, all other things being equal.
Unlike a conventional communication system, however, a DSSS system does have a certain resistance against narrowband interference, as the interference is not subject to the process gain of the DSSS signal and hence the signal-to-interference ratio is improved.
In Frequency Modulation (FM), the processing gain can be expressed as:
Gp is the processing gain
Bn is the Noise Bandwidth
Δf is the peak frequency deviation and
W is the sinusoidal modulating frequency.
|
Famous quotes containing the words process and/or gain:
“The invention of photography provided a radically new picture-making processa process based not on synthesis but on selection. The difference was a basic one. Paintings were madeconstructed from a storehouse of traditional schemes and skills and attitudesbut photographs, as the man on the street put, were taken.”
—Jean Szarkowski (b. 1925)
“Do not gain basely; base gain is equal to ruin.”
—Hesiod (c. 8th century B.C.)