Wireless Network Troubleshooting: Antennas, Channel Utilization, Site Surveys, and AP Association

Vocabulary flashcards covering key terms from the wireless networking lecture notes.

Omnidirectional antenna

An antenna that radiates RF equally in all directions around the antenna; typically mounted vertically; signal strength (RSSI) decreases with distance.

Dipole antenna (bidirectional)

An antenna that radiates primarily in two directions; yields higher RSSI in those two directions at greater distance; not widely used in Wi‑Fi.

Yagi antenna

Unidirectional antenna that concentrates energy in a single direction, allowing longer reach with less power; often used for point-to-point links between sites.

Parabolic dish antenna

Unidirectional, high-gain antenna for long-distance site‑to‑site links; focuses energy in one direction and is suitable for connecting buildings.

Polarization

Orientation of the electric field of RF waves; in Wi‑Fi, typically vertical or horizontal; misalignment can degrade RSSI.

Vertical polarization

Common Wi‑Fi polarization where antenna radiates upward; often used to maximize coverage in typical environments.

Horizontal polarization

Polarization where RF fields are oriented horizontally; may reduce coverage in some indoor scenarios; vertical is usually preferred.

RSSI (Received Signal Strength Indicator)

Measured signal strength (in dBm); more negative values indicate weaker signal; example: -30 to -40 dBm near AP, -65 to -70 dBm at ~100 ft.

Channel utilization

Measure of airtime usage on a wireless channel; high utilization leads to slower throughput; target is typically under ~30%.

2.4 GHz channels 1, 6, 11

Non-overlapping channels in the 2.4 GHz band; other channels overlap and can cause interference in dense deployments.

5 GHz spectrum

Higher Wi‑Fi band with many non-overlapping channels (about 24); generally less congestion and higher capacity than 2.4 GHz.

Site survey

Wireless survey to plan coverage, data rates, capacity, roaming, and QoS; determines AP locations, transmit power (EIRP), and potential interference.

EIRP (Effective Isotropic Radiated Power)

Combined measure of transmitter power and antenna gain that describes the strength of the transmitted signal.

Probe request

Broadcast frame sent by a client to discover nearby 802.11 networks (APs) in range.

Probe response

AP reply to a probe containing SSID, supported data rates, encryption, and capabilities.

802.11 authentication frame

Low-level frame that begins the authentication handshake between client and AP.

Deauthentication frame

Frame that terminates communication if the client is not authenticated or disconnects.

Association request

Client requests to associate with an AP, sending capabilities and encryption information.

Association response

AP's reply confirming successful association and providing an Association ID.

Association ID

Unique identifier assigned to the client‑AP association.

DHCP (Dynamic Host Configuration Protocol)

Protocol used to assign IP addresses to clients after association so they can use the network.

BSSID (Basic Service Set Identifier)

MAC address of the access point used to identify a specific AP in a network.

SSID (Service Set Identifier)

Human-readable network name announced by an AP for clients to join.

CSMA/CA (Collision Avoidance)

Wi‑Fi access method where devices listen before transmitting and use backoff to avoid collisions.

Clear Channel Assessment (CCA)

Step in CSMA/CA where a device listens to determine if the channel is free before transmitting.