CSCI 60 Set 1

yep

Human Communication

Rich, context-dependent exchange of information using multiple senses and unpredictable language.

Data Communication

Precise, machine-to-machine exchange that replicates information exactly without interpretation.

Analog Signal

A continuous waveform that varies smoothly over time and can take any value within a range.

Digital Signal

A discrete waveform that maintains constant levels, switching abruptly between defined values.

Spectrum

The complete range of frequencies over which a signal may vary.

Bandwidth

The width of the usable frequency spectrum; increasing this enables higher data rates.

Amplitude (A)

The height of a signal’s waveform, measured in volts, indicating signal strength.

Frequency (f)

The number of waveform cycles per second, measured in Hertz (Hz).

Period (T)

The time required for one complete cycle of a waveform; T = 1 / f.

Phase (Φ)

The relative position of a waveform in time, measured in degrees.

Signal Modulation

Technique of encoding information onto a carrier wave by altering amplitude, frequency, or phase.

Amplitude Modulation (AM)

Modulation method where the carrier’s amplitude varies with the information signal.

Frequency Modulation (FM)

Modulation method where the carrier’s frequency varies with the information signal.

Phase Modulation (PM)

Modulation method where the carrier’s phase is shifted according to the information signal.

Digitization

Conversion of analog information into discrete binary symbols for digital processing.

Bit

The smallest unit of digital data, representing a 0 or 1.

Byte

A group of eight bits treated as a single character or value.

ASCII

7-bit code mapping 128 characters for text representation in computers and networks.

Unicode

Universal character encoding standard (ISO 10646) capable of representing global scripts.

UTF-8

Variable-length Unicode encoding compatible with ASCII, widely used on the web.

Pixel

Smallest addressable element of a digital image;

Lossy Compression

Data reduction method that discards some information to achieve high compression ratios (≈10:1–20:1).

Lossless Compression

Data reduction method that preserves all original information, typically achieving <5:1 ratios.

Nyquist Sampling Theorem

Principle stating sampling rate must be at least twice the highest frequency to capture a signal accurately.

Pulse Code Modulation (PCM)

Technique that samples analog audio and encodes amplitudes into binary values.

Sampling Rate

Number of samples taken per second when digitizing analog signals, measured in samples/s.

Baseband Transmission

Digital signaling that uses the full channel bandwidth for a single data stream; bidirectional on demand.

Broadband Transmission

Analog signaling that divides bandwidth into multiple channels, supporting simultaneous signals.

Multiplexing

Sharing a transmission medium by combining multiple signals into distinct channels.

Frequency Division Multiplexing (FDM)

Analog multiplexing that allocates separate frequency bands, separated by guard bands, to each signal.

Time Division Multiplexing (TDM)

Digital multiplexing that assigns fixed time slots to each signal in repeating frames.

Statistical TDM (STDM)

Intelligent TDM that dynamically allocates time slots only when terminals have data to send.

Code Division Multiplexing (CDM)

Spread-spectrum multiplexing where users share time and frequency simultaneously via unique codes.

Simplex Mode

One-way communication channel where data flows in only one direction.

Half-Duplex Mode

Two-way alternate communication where devices take turns transmitting on a single path.

Full-Duplex Mode

Two-way simultaneous communication requiring separate logical paths for send and receive.

Parallel Transmission

Method that sends all bits of a group simultaneously across multiple wires.

Serial Transmission

Method that sends bits sequentially over a single channel or wire.

Asynchronous Transmission

Serial communication that frames each character with start/stop bits for timing without shared clock.

Synchronous Transmission

Serial communication that sends large blocks of data in sync with a shared clock signal.

Isochronous Transmission

Hybrid method delivering asynchronous data at regular, timed intervals controlled by the network.

Modem

Device that modulates digital data into analog form for transmission and demodulates it back on receipt.

Codec

Device or algorithm that converts analog signals to digital form and back again (coder-decoder).

Data Terminal Equipment (DTE)

End-user device responsible for generating or consuming digital data, e.g., computer or terminal.

Data Circuit-terminating Equipment (DCE)

Device that provides the interface between DTE and the transmission medium, e.g., modem.

Propagation Delay

Time required for an electromagnetic signal to travel from sender to receiver.

Attenuation

Loss of signal strength over distance, often countered by amplifiers or regenerators.

Latency

Overall delay between sending a request and receiving a response in a network.

Carrier Signal

Continuous waveform of constant frequency used as the basis for modulation.

Guard Band

Unused frequency space placed between FDM channels to prevent interference.

Telephone Network (PSTN)

Global circuit-switched network specialized for voice but capable of data, fax, and video calls.

Local Exchange (LEX) / Central Office (CO)

Switching center that aggregates subscriber lines within a local area.

Tandem Office (TO)

Regional switch that interconnects multiple local exchanges.

International Gateway Facility (IGF)

Exchange that routes calls between domestic networks and foreign carriers.

Local Loop

Physical circuit connecting a subscriber’s premises to the local exchange.

POTS

Plain Old Telephone Service—basic analog voice service over copper loops.

DTMF

Dual-Tone Multi-Frequency signaling used for tone dialing on telephones.

E.164 Numbering Plan

ITU-T global standard defining the format of public telephone numbers.

DS/T-Carrier Hierarchy

North American digital TDM levels from DS0 (64 kbps) to DS5 (~400 Mbps).

E-Carrier Hierarchy

European/Asian digital TDM levels from E0 (64 kbps) to E5 (~565 Mbps).

Optical Carrier (OC) Levels

SONET/SDH optical line rates, e.g., OC-3 = 155.52 Mbps, OC-192 ≈ 10 Gbps.

Response Time

Interval between a user action and the system’s complete reply; in networks, part of latency.

Baseband vs. Broadband

Baseband uses single-channel digital signaling; broadband uses multiple analog channels via modulation.

Sampling (Audio)

Measuring an analog signal’s amplitude at uniform intervals to create a digital representation.

Image Pixelization

Process of dividing an image into discrete pixels for digital storage and transmission.

Bandwidth Requirements

Data rate needed to transmit different media types (text, audio, video) without quality loss.