Cabling Part 1 by Andrew Oliviero

Author:Andrew Oliviero
Language: eng
Format: epub
Publisher: Wiley
Published: 2014-03-01T16:00:00+00:00

Spread Spectrum

Spread-spectrum transmissions use the same frequencies as other radio-frequency transmissions, but they use several frequencies simultaneously rather than just one. Two modulation schemes can be used to accomplish this: direct frequency modulation and frequency hopping.

Direct frequency modulation is the most common modulation scheme. It works by breaking the original data into parts (called chips), which are then transmitted on separate frequencies. To confuse eavesdroppers, spurious signals can also be transmitted. The transmission is coordinated with the intended receiver, which is aware of which frequencies are valid. The receiver can then isolate the chips and reassemble the data while ignoring the decoy information. Figure 12-7 illustrates how direct frequency modulation works.

Figure 12-7 Direct frequency modulation

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