CWTS flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

802.11ax OFDMA

Orthogonal frequency-division multiple access divides a channel into resource units so multiple clients transmit simultaneously, reducing overhead and improving efficiency in dense environments compared with OFDM's one-client-per-transmission model.

WMM access categories

Wi-Fi Multimedia defines four access categories: voice, video, best effort, and background. Higher-priority categories use smaller contention windows and shorter arbitration interframe spaces to gain channel access first.

802.11r fast transition

Fast BSS transition pre-authenticates a client with neighboring APs in a mobility domain, so roaming skips full 802.1X authentication and completes in tens of milliseconds instead of seconds.

WPA3 SAE

Simultaneous Authentication of Equals replaces the WPA2 pre-shared key handshake with a password-authenticated key exchange, providing forward secrecy and resistance to offline dictionary attacks on captured handshakes.

802.3at PoE+

PoE+ delivers up to 30 watts at the power sourcing equipment and guarantees 25.5 watts at the powered device, enough for 802.11ac/ax access points with two radios at higher transmit power.

CWNA certification scope

The CWNA exam covers RF fundamentals, 802.11 PHY and MAC layers, wireless security basics, site survey concepts, and WLAN troubleshooting, serving as the foundational CWNP credential beneath CWSP, CWDP, and CWAP.

Spatial streams

Independent data paths transmitted simultaneously over the same channel using multiple antennas. The AP and client negotiate the minimum stream count supported by both, so a 4x4 AP with a 2x2 client uses two streams.

EIRP calculation

Effective isotropic radiated power equals the transmitter power in dBm plus antenna gain in dBi minus cable and connector loss in dB. Regulators cap EIRP, so antenna gain must be balanced against radio power.

CAPWAP ports

The Control and Provisioning of Wireless Access Points protocol uses UDP 5246 for control messages and UDP 5247 for encapsulated data. Both must be permitted between APs and the controller for join and client traffic.

Controller-less architecture

Access points run a virtual controller function or are cloud-managed, distributing configuration and roaming decisions without dedicated hardware. This scales well for many sites but depends on network connectivity to the management plane.

Adapter calibration

Site survey adapters report RSSI with vendor-specific offsets. Calibrating the survey adapter against a known reference AP power normalizes readings so measured values match actual signal levels and design thresholds.

Antenna polarization

The orientation of the electric field relative to the antenna. Mismatched polarization between transmitter and receiver, such as one vertical and one horizontal, causes significant signal loss, so AP antennas should stay vertical.

Free-space path loss

Signal attenuation over distance in open space, computed as 32.44 plus 20 log of frequency in MHz plus 20 log of distance in km. Doubling distance or frequency adds roughly 6 dB of loss.

Signal-to-noise ratio

SNR equals received signal in dBm minus the noise floor in dBm. Higher SNR supports higher modulation and coding schemes; roughly 25 dB or better is needed for reliable high-throughput operation.

Non-overlapping 2.4 GHz channels

In North America, channels 1, 6, and 11 are the only three non-overlapping 20 MHz channels because channels are spaced 5 MHz apart. Overlapping channels cause adjacent-channel interference.

DFS channels

Dynamic frequency selection channels in the 5 GHz UNII-2 and UNII-2C bands are shared with radar. APs must detect radar and vacate the channel, so clients may see brief outages on these channels.

Fresnel zone clearance

The elliptical volume around a point-to-point link where signal energy travels. At least 60 percent of the first Fresnel zone must be unobstructed by terrain or structures to avoid excessive diffraction loss.

Multipath and delay spread

Signals reflecting off surfaces arrive at different times, causing fading and intersymbol interference. OFDM guard intervals and MIMO diversity mitigate multipath, but excessive delay spread beyond the guard interval degrades performance.

Co-channel interference

Two access points or clients transmitting on the same channel in overlapping coverage areas. They contend for airtime and lower throughput; proper channel reuse planning and power control reduce it.

AP-on-a-stick survey

A validation survey that places a single AP at candidate mounting locations and measures signal and SNR at test points, confirming that the predictive design achieves coverage and capacity targets before full installation.

Predictive site survey

Software modeling of coverage using floor plans, wall attenuation values, and AP specifications. It estimates placement and channel plans before hardware is installed and is validated later with on-site measurements.

Coverage design threshold

A common target for voice-grade coverage is -67 dBm RSSI or better with at least 25 dB SNR at cell edges, ensuring reliable modulation and handoff between access points.

Cell edge overlap

Adjacent AP coverage areas should overlap by roughly 15 to 20 percent so clients can roam before signal drops too low, while avoiding excessive overlap that increases co-channel interference.

As-built documentation

The final record of installed AP locations, channel and power settings, cable and PoE runs, and survey heat maps. It supports future troubleshooting, capacity changes, and compliance audits.

Hidden node problem

Two clients can each hear the AP but not each other, so their transmissions collide at the AP. RTS/CTS can reduce collisions, but denser AP placement is usually the more effective fix.

Sticky client behavior

A client stays associated with a distant AP even when a closer one offers better signal, because its roaming threshold is set too low. Balanced AP power and 802.11k/v help correct it.

Airtime utilization

The percentage of time a channel is busy with transmissions. High utilization, often above 50 to 60 percent, indicates congestion; legacy clients, retries, and too many clients per AP drive it up.

Four-way DHCP exchange

Discover, Offer, Request, Acknowledge. Capturing these frames confirms whether a client received an address; a missing Offer usually points to VLAN mismatch or relay problems.

Monitor-mode capture

A wireless adapter in monitor mode captures raw 802.11 frames on a selected channel, including management and control frames, enabling analysis of association, authentication, and EAPOL exchanges.

802.1X EAP-TLS

An authentication method where both client and server present X.509 certificates to the RADIUS server. It avoids password-based weaknesses and is considered the strongest common EAP type.

RADIUS shared secret

A pre-shared string configured on both the authenticator and the RADIUS server. Mismatched secrets cause authentication failures that may appear only in server logs, not on the client.

Management frame protection

Defined by 802.11w, it cryptographically protects deauthentication, disassociation, and action frames, preventing spoofed deauth attacks that disconnect clients. It can be optional or required per SSID.