Differentiate between wireless deployment types (autonomous, controller-based)
Describe site survey basics and AP placement strategies
802.11 Standards
Wi-Fi is governed by the IEEE 802.11 family of standards. Each amendment defines different frequencies, modulation schemes, and maximum data rates. The Wi-Fi Alliance also assigns marketing names (Wi-Fi 4, 5, 6, etc.).
Standard
Wi-Fi Name
Frequency
Max Speed
Year
802.11a
--
5 GHz
54 Mbps
1999
802.11b
--
2.4 GHz
11 Mbps
1999
802.11g
--
2.4 GHz
54 Mbps
2003
802.11n
Wi-Fi 4
2.4 / 5 GHz
600 Mbps
2009
802.11ac
Wi-Fi 5
5 GHz
6.9 Gbps
2013
802.11ax
Wi-Fi 6/6E
2.4 / 5 / 6 GHz
9.6 Gbps
2020
802.11be
Wi-Fi 7
2.4 / 5 / 6 GHz
46 Gbps
2024
Key Distinction:
2.4 GHz has better range and wall penetration but only 3 non-overlapping channels (1, 6, 11). 5 GHz offers more channels and less interference but shorter range. 6 GHz (Wi-Fi 6E/7) adds even more channels with minimal congestion.
Frequency Bands and Channels
/* 2.4 GHz Band -- 11 channels (US), only 3 non-overlapping */
Channel: 1 2 3 4 5 6 7 8 9 10 11
|---|---|---|---|---|---|---|---|---|---|
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Ch 1 (22MHz) Ch 6 (22MHz) Ch 11 (22MHz)
/* Best practice: use channels 1, 6, and 11 only.
Overlapping channels cause co-channel interference. *//* 5 GHz Band -- 25 non-overlapping 20MHz channels (US)
Can bond channels: 40MHz, 80MHz, 160MHz for higher throughput
More channels = less interference, better for dense environments *//* 6 GHz Band (Wi-Fi 6E) -- 59 new 20MHz channels
Clean spectrum, no legacy devices, ideal for high-density */
Wireless Security Protocols
Protocol
Encryption
Status
Notes
WEP
RC4 (40/104-bit)
BROKEN
Crackable in minutes. Never use.
WPA
TKIP (RC4-based)
Deprecated
Interim fix for WEP. Vulnerabilities found.
WPA2-Personal
AES-CCMP
Current standard
Pre-shared key (PSK). Vulnerable to offline dictionary attacks if weak password.
WPA2-Enterprise
AES-CCMP
Current standard
802.1X/RADIUS authentication. Per-user credentials. Best for organizations.
WPA3-Personal
AES-GCMP / SAE
Latest
SAE (Simultaneous Authentication of Equals) replaces PSK. Resistant to offline attacks.
WPA3-Enterprise
192-bit AES
Latest
CNSA-grade encryption. Required for government/military.
Real-World Minimum:
Always use WPA2-AES or WPA3 at minimum. WEP and WPA-TKIP are crackable with freely available tools (aircrack-ng). For enterprise networks, WPA2/3-Enterprise with 802.1X is the standard -- each user authenticates with unique credentials through a RADIUS server.
How Wireless Communication Works
Unlike wired Ethernet, wireless devices cannot detect collisions (they are transmitting and receiving on the same antenna). Instead, 802.11 uses CSMA/CA (Collision Avoidance) -- devices listen before transmitting and use acknowledgments to confirm delivery.
/* CSMA/CA Process */1. Client wants to transmit
2. Listens to the channel (carrier sense)
3. If busy: wait + random backoff timer
4. If clear: send RTS (Request to Send) to AP
5. AP responds with CTS (Clear to Send)
6. Client transmits data frame
7. AP sends ACK (acknowledgment)
8. If no ACK received: retransmit
/* Key difference from wired CSMA/CD:
- Wired: detect collision, stop, backoff, retry
- Wireless: AVOID collision by checking first + RTS/CTS
- The "hidden node" problem: two clients can't hear each other
but both reach the AP. RTS/CTS solves this. */
Wireless Architecture
Autonomous APEach access point is configured individually. No central management. Works for small deployments (1-5 APs). Each AP manages its own SSIDs, channels, and security.
Controller-Based (WLC)A Wireless LAN Controller manages all APs centrally. APs are "lightweight" (CAPWAP tunnel). Policies pushed from one console. Required for enterprise (50+ APs).
Cloud-ManagedAPs are managed through a cloud dashboard (Meraki, Aruba Central, UniFi). No on-prem controller. Easy deployment, subscription-based.
Mesh NetworkingAPs connect wirelessly to each other to extend coverage without cabling. One AP connects to the wired network; others relay through it. Good for outdoor or hard-to-wire areas.
Site Surveys and AP Placement
A wireless site survey maps RF coverage before deploying APs. The goal is to ensure adequate signal strength, minimize dead zones, and avoid co-channel interference.
/* Site Survey Types */Passive Survey: Walk the site with a survey tool (Ekahau, NetSpot)
listening to existing signals. Maps current RF environment.
Active Survey: Connect to the network and measure actual throughput,
latency, and packet loss at each location.
Predictive: Use software to simulate RF propagation on a floor plan
before any hardware is deployed.
/* Key Metrics */
Signal Strength: Minimum -67 dBm for VoIP, -70 dBm for data
SNR: Minimum 25 dB for reliable performance
Channel Overlap: APs on same channel should have -19 dBm separation
/* AP Placement Rules of Thumb */
- Mount APs on the ceiling, antenna pointing down
- Space APs 40-60 feet apart for 5 GHz, 80-100 for 2.4 GHz
- Avoid placing near metal objects, concrete, or microwave ovens
- Use 20-30% overlap between adjacent AP coverage areas for roaming
Common Wireless Issues
Co-Channel InterferenceAdjacent APs on the same channel compete for airtime. Solution: proper channel planning using non-overlapping channels.
Adjacent Channel InterferenceAPs on overlapping channels (e.g., 1 and 3 in 2.4 GHz) corrupt each other's signals. Worse than co-channel. Use only 1, 6, 11.
Hidden NodeTwo clients cannot hear each other but both reach the AP, causing collisions at the AP. Solved with RTS/CTS.
Sticky ClientsDevices stay connected to a distant AP instead of roaming to a closer one. Minimum RSSI thresholds and band steering help.
Key Takeaways
802.11ac (Wi-Fi 5) and 802.11ax (Wi-Fi 6) are current standards; Wi-Fi 7 is emerging