Chapter 2

Signals

Data exchanged between two parties that travels through the network.

Analog Signals

Signals that can take many values.

Digital Signals

Signals that take a limited number of values.

Peak Amplitude

Maximum signal intensity, measured in volts.

Period (T)

Time taken for one complete cycle of a signal.

Frequency (f)

Number of cycles per second, measured in Hertz (Hz).

Phase

Position of the wave relative to time 0, measured in degrees or radians.

Wavelength (λ)

Distance that a signal travels in one period.

Bit Rate

Number of bits transmitted per second (bps).

Decibels (dB)

Measure of signal strength; negative dB indicates loss, positive dB indicates gain.

Attenuation

Loss of signal energy as it travels through a medium.

Amplification

Used to restore signal strength.

Distortion

Occurs when the signal changes shape during transmission.

Noise

Unwanted interference that alters the signal.

Signal-to-Noise Ratio (SNR)

Measures signal strength compared to noise.

Nyquist Bit Rate

Formula for the bit rate in a noiseless channel.

Shannon Capacity

Determines the upper limit of data rate in real-world conditions.

Throughput

Actual data transfer rate, always lower than bandwidth.

Latency

Total time for data to travel from sender to receiver.

Bandwidth-Delay Product

Defines how much data can fill a link at any moment.

Jitter

Variation in delay between received packets.

Digital-to-Digital Conversion

Converts digital data into a digital signal for transmission.

Line Coding

Converts digital data (bits) into a digital signal.

Block Coding

Introduces redundancy to improve synchronization and error detection.

Pulse Code Modulation (PCM)

Most common method for digitizing analog signals.

Delta Modulation (DM)

Records changes in the signal amplitude from the previous sample.

Multiplexing

Technique that enables multiple signals to be transmitted simultaneously over one data link.

Frequency-Division Multiplexing (FDM)

Analog technique that uses unique carrier frequencies for each signal.

Time-Division Multiplexing (TDM)

Digital technique that allocates time slots to different connections.

Twisted-Pair Cable

Two copper wires twisted together to reduce interference.

Coaxial Cable

Central conductor with insulation and shielding, used in telecommunications.

Fiber-Optic Cable

Uses light signals through a glass/plastic core for low attenuation and high bandwidth.

Radio Waves

Electromagnetic waves suitable for long-range broadcasts.

Microwaves

Require line-of-sight communication, used in cellular networks.

Infrared

Short-range communication that cannot penetrate walls.