Physical Layer, Wireless & Cellular Networking Vocabulary

Vocabulary flashcards covering key terms from the lecture on the physical layer, wireless media, Wi-Fi, Bluetooth, and cellular technologies from 1G to 5G.

Physical Layer

OSI layer that transports bits of a data-link frame across the network media by encoding them into physical signals.

Network Interface Card (NIC)

Electronic adapter that connects a device to a wired network; provides a physical interface for sending/receiving frames.

WLAN NIC

Wireless network interface card that connects a device to a Wi-Fi network instead of a wired LAN.

International Organization for Standardization (ISO)

Global body that develops and publishes international networking and other technical standards.

TIA/EIA

Telecommunications Industry Association/Electronic Industries Association; sets many cabling and connector standards.

International Telecommunication Union (ITU)

UN agency that coordinates global telecom standards and spectrum allocation.

American National Standards Institute (ANSI)

U.S. organization that approves and publishes national standards, including networking protocols.

Institute of Electrical and Electronics Engineers (IEEE)

Professional society that creates widely used network standards such as Ethernet (802.3) and Wi-Fi (802.11).

Copper Cable

Physical medium that carries data as electrical pulses; subject to attenuation, EMI, and crosstalk.

Fiber-Optic Cable

Medium that transports data as light pulses, offering high bandwidth, long distance, and immunity to EMI/RFI.

Wireless Media

Transmission medium that carries data as radio or microwave signals through the air.

Encoding (Physical Layer)

Process of converting a bit stream into a predefined code recognizable by sender and receiver.

Signaling (Physical Layer)

Technique that represents binary 1s and 0s as specific physical signal types (voltage, light, RF).

Bandwidth

Capacity of a medium to carry data, typically measured in kb/s or Mb/s.

Throughput

Actual rate at which bits travel from sender to receiver; usually lower than the theoretical bandwidth.

Instantaneous Throughput

Throughput measured at a specific moment in time.

Average Throughput

Throughput measured over a longer interval, smoothing out short-term fluctuations.

Bottleneck Link

Slowest link on an end-to-end path that constrains overall throughput.

Electromagnetic Interference (EMI)

External electromagnetic signals that distort data carried on copper cables.

Radio Frequency Interference (RFI)

Interference caused by nearby radio transmitters that can corrupt copper-carried data.

Attenuation

Signal loss that increases with cable length, weakening data pulses.

Crosstalk

Disturbance where signals in one wire induce unwanted signals in adjacent wires.

Unshielded Twisted Pair (UTP)

Common copper cabling where wire pairs are twisted to reduce crosstalk; lacks additional shielding.

Shielded Twisted Pair (STP)

Twisted-pair cabling wrapped in conductive shielding to reduce EMI.

Coaxial Cable

Copper medium with a single conductor core and shielding; once common in broadband and cable TV.

Fiber-to-the-Home (FTTH)

Deployment of fiber-optic lines directly to residential premises.

Long-Haul Network

Fiber links spanning large geographic areas between cities or regions.

Submarine Cable Network

Undersea fiber cables that interconnect continents with high-capacity links.

Enterprise Network (Fiber)

In-building or campus fiber-optic infrastructure used by organizations.

Coverage Area (Wireless)

Geographic zone within which a wireless signal can be effectively received.

Hidden Terminal Problem

Wi-Fi issue where two devices that cannot hear each other transmit simultaneously and collide at an access point.

Signal-to-Noise Ratio (SNR)

Ratio of signal power to background noise; higher values mean easier signal extraction and lower BER.

Free Space Path Loss

Power loss of a radio signal over distance, proportional to (frequency × distance)².

Multipath Propagation

Phenomenon where radio waves reflect off objects, causing signals to arrive at slightly different times.

Coherence Time

Time interval over which the channel’s characteristics remain constant; limits maximum data rate.

IEEE 802.11b

1999 Wi-Fi standard: 11 Mb/s at 2.4 GHz, ~30 m range.

IEEE 802.11g

2003 Wi-Fi standard: 54 Mb/s at 2.4 GHz, ~30 m range.

IEEE 802.11n (Wi-Fi 4)

2009 Wi-Fi standard: up to 600 Mb/s at 2.4/5 GHz, ~70 m range.

IEEE 802.11ac (Wi-Fi 5)

2013 Wi-Fi standard: up to 3.47 Gb/s at 5 GHz, ~70 m range.

IEEE 802.11ax (Wi-Fi 6)

2020 Wi-Fi standard: up to 14 Gb/s at 2.4/5 GHz, ~70 m range.

IEEE 802.11af

2014 Wi-Fi variant using unused TV bands; up to 560 Mb/s, ~1 km range.

IEEE 802.11ah

2017 Wi-Fi variant at 900 MHz; up to 347 Mb/s, ~1 km range.

Basic Service Set (BSS)

A single Wi-Fi cell consisting of an access point and all associated wireless hosts.

Access Point (AP)

Base station in a Wi-Fi network that connects wireless hosts to the wired infrastructure.

Service Set Identifier (SSID)

Human-readable name broadcast by an AP to identify a Wi-Fi network.

Passive Scanning

Association method where a host listens for beacon frames from APs before selecting one.

Active Scanning

Process where a host broadcasts Probe Requests and listens for Probe Responses from APs.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance; Wi-Fi’s method to reduce transmission collisions.

Rate Adaptation (802.11)

Dynamic adjustment of modulation scheme and data rate based on current SNR.

Power Management (802.11)

Wi-Fi feature allowing devices to sleep between beacon frames to save battery.

Bluetooth

Short-range (≈10 m) wireless technology replacing cables for peripherals; operates at 2.4 GHz.

Piconet

Ad-hoc Bluetooth network with one master and up to seven active slave devices.

Time Division Multiplexing (TDM)

Technique where users share a channel by transmitting in distinct time slots.

Frequency Division Multiplexing (FDM)

Method where multiple signals share a medium by occupying separate frequency channels.

1G

First-generation cellular networks providing analog voice with FDMA; <0.5 Mb/s.

2G

Digital cellular generation (e.g., GSM, D-AMPS) using TDMA/CDMA to increase voice capacity and add SMS/data.

3G

Cellular generation (e.g., WCDMA, CDMA2000) introducing mobile broadband data services.

4G LTE

All-IP cellular standard offering 100 + Mb/s data rates using OFDMA, MIMO, and carrier aggregation.

5G NR

Fifth-generation cellular radio using FR1 and FR2 bands, aiming for 10× speed, 10× lower latency than 4G.

Orthogonal Frequency-Division Multiple Access (OFDMA)

4G/5G downlink multiple-access scheme that divides spectrum into narrow orthogonal subcarriers.

Multiple-Input Multiple-Output (MIMO)

Technique using multiple antennas to transmit parallel data streams and improve throughput/reliability.

Carrier Aggregation

LTE feature that combines several frequency blocks (up to 100 MHz) to boost data rates.

Enhanced Packet Core (EPC)

All-IP core network of LTE that routes user and control traffic.

User Equipment (UE)

End-user device with LTE/5G radio, identified by an IMSI stored on a SIM card.

eNode-B

LTE base station providing the radio interface between UEs and the EPC.

Mobility Management Entity (MME)

LTE control-plane node handling authentication, mobility, and session management.

Serving Gateway (S-GW)

EPC data-plane node that routes user packets between eNode-Bs and the core network.

PDN Gateway (P-GW)

EPC gateway connecting LTE core to external packet data networks such as the Internet.

Home Subscriber Service (HSS)

Central LTE database storing subscriber profiles and authentication credentials.

Packet Data Convergence Protocol (PDCP)

LTE link-layer subprotocol that handles header compression and encryption.

Radio Link Control (RLC)

LTE layer responsible for fragmentation, reassembly, and reliable data transfer.

Medium Access Control (MAC) – LTE

Layer that schedules and handles access to radio resources (transmission slots) for UEs.

Millimeter Wave (mmWave)

24–52 GHz 5G frequency range enabling very high data rates over short distances.

Pico-cell

Very small 5G cell (10–100 m diameter) required for dense mmWave deployments.

Subscriber Identity Module (SIM)

Smart card containing IMSI and keys that authenticate a mobile subscriber to the network.

International Mobile Subscriber Identity (IMSI)

Unique 64-bit number identifying a mobile user within cellular networks.