Introduction to Computer Networking, Architectures, and Topologies

1. WLAN Key Characteristics

• Half-Duplex Transmission: Devices share the same frequency for sending and receiving
• Environmental Impact: Walls, water, and metals attenuate signals
• Higher frequencies → higher data rate, lower range | Lower frequencies → wider range, lower data rate

2. Wireless Standards Organizations

Organization	Purpose
IEEE	Develops and maintains operational standards
FCC	Regulates wireless usage in the U.S.
ETSI	European telecommunications standards
Wi-Fi Alliance	Promotes device interoperability
WLANA	Educates consumers about WLANs

3. IEEE 802.11 Standards

Standard	Year	Frequency	Data Rate
802.11b	1999	2.4 GHz	11 Mbps
802.11a	1999	5 GHz	54 Mbps
802.11g	2003	2.4 GHz	54 Mbps
802.11n	2010	2.4/5 GHz	Up to 300 Mbps
802.11ac	2013	5 GHz	Up to 1 Gbps
802.11ax	2021	2.4/5/6 GHz	Up to 9.6 Gbps

4. Wi-Fi 5 vs Wi-Fi 6 Comparison

Parameter	Wi-Fi 5	Wi-Fi 6
Frequency	5 GHz	2.4/5/6 GHz
Channel Width	Up to 160 MHz	Up to 160 MHz
Data Rate	Up to 3.5 Gbps	Up to 9.6 Gbps
Modulation	256-QAM	1024-QAM
User Capacity	4	8

5. Cellular Technologies

Generation	Bandwidth	Standard
3G	2 Mbps	WCDMA, CDMA-2000
4G/LTE	200–1000 Mbps	LTE, WiMAX
5G	Up to 10 Gbps	mmWave, MIMO

6. WLAN Components

• WAP: Bridge between wireless devices and LAN
• NIC: Internal or USB wireless adapter
• Antennas:
  • Omni-directional: 360° coverage
  • Yagi (Directional): Long range, focused beam

7. WLAN Deployment Modes

• Ad Hoc: Direct device-to-device communication
• Infrastructure: Devices connect via AP to LAN

8. Wireless Controllers and AP Management

• Thick APs: Independently managed
• Thin APs: Centrally managed via WLC with CAPWAP
• VLAN Pooling: Helps reduce broadcast domain

9. Antenna Gain Units

dBi: Relative to an isotropic antenna  
dBd: Relative to dipole antenna  
dBd = dBi - 2.2  
Examples:  
Yagi 7 dBd → 9.2 dBi  
Omni 4.8 dBd → 7 dBi

10. Site Survey

• Collect user and coverage requirements
• Identify obstacles and signal overlap
• Use tools like Ekahau or AirMagnet
• Optimize signal strength across floors

11. WLAN Security

Threats:

• Rogue APs
• Unmonitored Ad Hoc networks
• DoS attacks via jamming or spoofing
• Passive attacks like packet sniffing

Defenses:

• Use WLC with CAPWAP protocol
• Send Deauthentication frames
• Enable MFP (Management Frame Protection)
• Deploy Wireless IDS/IPS

Security Mechanisms:

• Open Access: Public networks (no encryption)
• WEP: Weak encryption, vulnerable
• WPA: Dynamic TKIP encryption
• WPA2: Strong AES-CCMP encryption (recommended)
• MAC Filtering: Device-based access control (spoofable)
• PSK: Shared password between AP and device