CWNA key terms

An elliptical tunnel of space surrounding the straight line between two antennas, through which most of the radio energy travels. Obstructions inside the first zone weaken the signal, so clearance matters for long outdoor links.

Effective Isotropic Radiated Power: the apparent power a radio system radiates in its strongest direction, found by adding transmit power and antenna gain and subtracting cable loss. Regulators cap EIRP for each band and country.

Received Signal Strength Indicator: a relative number a client or access point reports for incoming signal strength. It uses vendor-specific scaling rather than true dBm, so values from different manufacturers cannot be compared directly.

Signal-to-Noise Ratio: the gap in decibels between the wanted signal and the background noise at the receiver. Higher values allow denser modulation; around 25 dB is a common design target for voice and data.

The same transmission arriving at a receiver over several paths because it reflected, diffracted, or scattered off objects, with each copy slightly delayed. The result can be fading and intersymbol interference, though MIMO can exploit it.

A calculation that adds every gain and subtracts every loss between transmitter and receiver - radio output, antenna gain, cable loss, path loss, fade margin - to predict whether a link will work.

How much more signal an antenna radiates in one direction than a theoretical isotropic radiator would, measured in dBi. The extra energy comes from focusing the pattern, so higher gain means a narrower beam.

The angle over which an antenna's main lobe stays within half its peak power, quoted for the horizontal and vertical planes. A narrower beam concentrates energy for longer reach but demands accurate aiming.

The plane in which an antenna's electric field oscillates, usually vertical or horizontal and sometimes circular. Both ends of a link should match, because a mismatch throws away a large part of the signal.

Multiple-Input Multiple-Output: radios with several transmit and receive chains and antennas that use spatial multiplexing, beamforming, and diversity to raise throughput, range, or reliability. Every modern 802.11 standard relies on it.

Voltage Standing Wave Ratio: a number describing how badly the antenna system's impedance matches the radio. Values near 1:1 mean almost all energy radiates; high values reflect power back and waste it as heat.

A device that connects wireless stations to a wired network, transmitting and receiving 802.11 frames while handling association, authentication, encryption, and channel access for the basic service set it creates.

A system that centrally configures, monitors, and upgrades many lightweight access points, and that provides RF management, roaming assistance, and consistent security policy. It can be hardware, virtual, or cloud-hosted.

Power over Ethernet: sending direct-current power to access points and other devices along the same twisted-pair cable that carries data. Common versions are 802.3af, 802.3at, and 802.3bt with increasing wattage.

Control and Provisioning of Wireless Access Points: the protocol that tunnels control and data traffic between lightweight access points and a WLAN controller over IP, optionally protected with DTLS encryption.

A logically separated Layer 2 broadcast domain created by switch configuration, letting devices share physical hardware while staying on different networks. Wireless designs usually map each SSID or user group to its own VLAN.

An access point behavior that nudges dual-band clients toward the 5 GHz or 6 GHz radio, keeping slower or older devices on 2.4 GHz and spreading load across the available spectrum.

Assigning the same channel to access points placed far enough apart that their cells do not overlap enough to interfere, so a limited set of channels can serve a large building.

The set of standards published by the Institute of Electrical and Electronics Engineers that defines wireless LAN physical layers and media access rules, including amendments marketed as Wi-Fi 4, 5, 6, and 7.

An industry consortium that certifies wireless products for interoperability and security, owns the Wi-Fi trademark, and defines programs such as WPA3 and Wi-Fi 6 branding.

The country or region setting in a wireless device that selects legal channels, maximum transmit power, and permitted features according to local spectrum rules, such as those enforced by the FCC or ETSI.

Basic Service Set: the smallest WLAN building block, made up of one access point's radio and all client stations associated with it, identified uniquely by a BSSID.

The 48-bit MAC address of an access point radio, used as the unique identifier of a single basic service set. Clients rely on it to tell apart overlapping cells that broadcast the same SSID.

Extended Service Set: two or more basic service sets linked by a common distribution system and sharing one SSID, which lets a client move between access points while keeping its network connection.

The 802.11 procedure in which a client chooses an access point, exchanges capability information, and joins that basic service set after link-layer authentication succeeds.

Orthogonal Frequency Division Multiple Access: splitting a channel into groups of subcarriers that can carry data for different clients at the same moment. Introduced to WLAN in 802.11ax to cut overhead in crowded cells.

A brief pause between OFDM symbols that stops delayed reflections of one symbol from corrupting the next. Shortening it raises throughput but requires cleaner RF conditions.

Port-based access control where a supplicant proves its identity through an authenticator to an authentication server before the network port opens. On WLANs it gives each user individual enterprise credentials.

The message exchange in WPA2 and WPA3 that proves both parties hold the pairwise master key, then derives and installs fresh keys for encrypting unicast and group traffic.

Simultaneous Authentication of Equals: the password-based method in WPA3-Personal that resists offline guessing by replacing the pre-shared key handshake with a peer-to-peer exchange that yields a unique session key.

Protected Management Frames, standardized as 802.11w: cryptographic protection for management frames such as deauthentication and disassociation, which blocks spoofed disconnect attacks. It is required for WPA3 and Wi-Fi 6 certification.

An access point installed without authorization, either plugged into the corporate network or broadcasting nearby, which can expose data, bypass policy, or lure clients into connecting to it.

Overlap between cells operating on the same channel, which makes stations defer to each other and sharply reduces throughput. Designers control it with spacing, power settings, and antenna choice.

Energy spilling from a nearby channel into the one in use because the channels are not separated enough, raising noise and causing retries. In 2.4 GHz, only channels 1, 6, and 11 avoid it.

A station that the access point hears clearly but other clients cannot hear, so its transmissions collide with theirs without anyone sensing the channel is busy. RTS/CTS exchanges reduce the damage.

A receiver that plots energy across a range of frequencies instead of decoding Wi-Fi frames, exposing non-802.11 interferers such as microwave ovens, cordless phones, video cameras, and radar.

A simulated survey built from floor plans, wall materials, and access point models before hardware is installed. It estimates AP count and placement, but real measurements should confirm the results.

A walk-through in which a client radio only listens, recording signal strength, noise, and channel use to build coverage maps. It shows what is present but not how the network performs under load.

A survey where the client associates with each access point and measures throughput, retries, and roaming behavior. It reflects real user experience but needs a fully configured network.

A site survey method that mounts an access point temporarily on a tripod at a candidate location, often on battery power, so real coverage can be measured before permanent installation.