Wireless Devices

Channels

Definition: Specific frequency segments within a band that wireless devices use to transmit data.
Channel width: Determines bandwidth/speed (e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz).
- Narrower = less interference, longer range; wider = higher throughput, more susceptible to interference.
Non-overlapping channels: Critical to avoid co-channel interference.
- 2.4 GHz: Only 3 non-overlapping (1, 6, 11 in most regions).
- 5 GHz: Many more (up to ~24 non-overlapping depending on region and width).
- 6 GHz: Even more available, fewer legacy devices, less congestion.
Regulatory impacts: Country-specific rules on allowed channels and power levels.
- 802.11h: Enables Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) to avoid radar interference (especially 5 GHz UNII-2 bands).

2.4 GHz:
- Channels 1–14 (region-dependent; US uses 1–11).
- Better range and penetration through walls.
- More crowded (Bluetooth, microwaves, cordless phones cause interference).
- Max practical throughput lower due to congestion and narrower channels.
5 GHz:
- Channels 36–165+ (more available, higher power allowed in some bands).
- Higher speeds, less interference, shorter range.
- Supports wider channels (80/160 MHz).
6 GHz (introduced with Wi-Fi 6E and Wi-Fi 7):
- Newest band, least congested.
- Wider channels (up to 160 MHz standard), very high throughput.
- Shorter range, requires Wi-Fi 6E/7 compatible devices.
Band steering: AP pushes dual/tri-band clients to less congested/higher-frequency bands (e.g., 5 GHz or 6 GHz over 2.4 GHz) for better performance.

Definition: Human-readable name of the wireless network (what users see in the list of available networks).
Basic Service Set Identifier (BSSID): MAC address of the specific access point (unique per AP radio).
Extended Service Set Identifier (ESSID): Same SSID shared across multiple APs for seamless roaming (common in enterprise/infrastructure setups).
Configuration tips:
- Hide SSID (not true security—devices still broadcast probes).
- Multiple SSIDs per AP (e.g., one for employees, one for guests).
- SSID length: Up to 32 characters.

Infrastructure mode: Most common; devices connect through an access point (AP) to a wired network.
Ad hoc (Independent Basic Service Set – IBSS): Peer-to-peer; devices connect directly without an AP (limited range, no central management).
Mesh networks: Multiple APs interconnect wirelessly to extend coverage (self-healing, no wired backhaul needed for all nodes).
Point-to-point: Directional links between two locations (e.g., building-to-building bridge, often uses directional antennas).

Wi-Fi Protected Access 2 (WPA2):
- Still widely used; AES-CCMP encryption.
- Vulnerable to KRACK attack (patched in most implementations).
Wi-Fi Protected Access 3 (WPA3):
- Current standard; stronger protection.
- WPA3-Personal: Uses Simultaneous Authentication of Equals (SAE) instead of PSK (resistant to offline dictionary attacks).
- WPA3-Enterprise: Enhanced 192-bit security suite options.
- Opportunistic Wireless Encryption (OWE): Encrypts open networks (no password needed, but protects against eavesdropping).
Legacy: Avoid WEP (insecure, broken) and WPA (TKIP vulnerable).

Purpose: Isolate untrusted users (visitors, BYOD) from internal network.
Features:
- Separate SSID/VLAN/subnet.
- Limited access (Internet only, no internal resources).
- Bandwidth throttling or time limits common.
Captive portals: Redirect users to login/agreement page before granting Internet access (common in hotels, cafes, enterprises).
Isolation: Client isolation prevents guests from communicating with each other.

Pre-shared key (PSK) / Personal:
- Single shared passphrase for all users.
- Easy setup, but weak if passphrase is poor or leaked.
- Used in homes/small offices.
Enterprise (802.1X):
- Uses RADIUS or similar server for per-user authentication.
- Supports certificates, usernames/passwords, EAP methods (EAP-TLS, PEAP, EAP-TTLS).
- Much more secure; individual revocation possible.
- Common in businesses.

Omnidirectional:
- Radiates signal in all directions (360° horizontal).
- Common in indoor APs for general coverage.
- Lower gain, shorter effective range in one direction.
Directional:
- Focuses signal in one direction (e.g., Yagi, patch, parabolic).
- Higher gain, longer range, used for point-to-point or targeted coverage.
- Reduces interference from unwanted directions.

Autonomous (fat) AP:
- Standalone; each AP configured/managed individually.
- Suitable for small deployments.
Lightweight (thin) AP:
- Managed centrally by a Wireless LAN Controller (WLC).
- Controller handles configuration, roaming, security policies.
- Uses protocols like CAPWAP (Control And Provisioning of Wireless Access Points).
- Better for enterprise-scale (seamless roaming, load balancing, centralized monitoring).

Frequencies: 2.4 = range/crowded; 5 = speed/less crowded; 6 = fastest/least crowded.
Channels: Avoid overlap → 1-6-11 (2.4 GHz); use DFS on 5 GHz radar bands.
Security progression: Open → WEP (avoid) → WPA → WPA2 → WPA3 (best).
Authentication: PSK = simple/shared; Enterprise = secure/individual.
Antennas: Omni = everywhere; Directional = focused/far.
Network types: Infrastructure = AP-based (most); Mesh = wireless backhaul; Ad hoc = no AP.

Review scenarios: "Choose best channel/frequency for high-density office" or "Configure secure guest network with isolation."