*
Data must be transformed into electromagnetic signals prior to transmission
across a network.

*
Data and signals can be either analog or digital.

*
A signal is periodic if it consists of a continuously repeating pattern.

*
Each sine wave can be characterized by its amplitude, frequency, and phase.

*
Frequency and period are inverses of each other.

*
A time-domain graph plots amplitude as a function of time.

*
A frequency-domain graph plots each sine wave’s peak amplitude against its
frequency.

*
By using Fourier analysis, any composite signal can be represented as a
combination of simple sine waves.

*
The spectrum of a signal consists of the sine waves that make up the signal.

*
The bandwidth of a signal is the range of frequencies the signal occupies.
Bandwidth is determined by finding the difference between the highest and
lowest frequency components.

*
Bit rate (number of bits per second) and bit interval (duration of 1 bit) are
terms used to describe digital signals.

*
A digital signal is a composite signal with an infinite bandwidth.

*
Bit rate and bandwidth are proportional to each other.

*
The Nyquist formula determines the theoretical data rate for a noiseless
channel.

*
The Shannon capacity determines the theoretical maximum data rate for a noisy
channel.

*
Attenuation, distortion, and noise can impair a signal.

*
Attenuation is the loss of a signal’s energy due to the resistance of the
medium.

*
The decibel measures the relative strength of two signals or a signal at two
different points.

*
Distortion is the alteration of a signal due to the differing propagation
speeds of each of the frequencies that make up a signal.

*
Noise is the external energy that corrupts a signal.

*
We can evaluate transmission media by throughput, propagation speed, and
propagation time.

*
The wavelength of a frequency is defined as the propagation speed divided by
the frequency.

Reference:

Data Communication and Networking

Fourth Edition

Behrouza A. Forouzan

Fourth Edition

Behrouza A. Forouzan

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