Wireless Networking
CPSC 330 - Fall 2003

(under development)

radio transmission

• FM - 88 MHz - 108 MHz
• wireless - 2.4 GHz and 5 GHz (can channel hop within band to avoid contention)

architectures

• base station - access point and end stations, access points wired to internet (802.11 typically used)
• peer-to-peer - can form ad-hoc networks

transmission characteristics

• bit error rate higher, so smaller packets are sent
• power - sleep mode (access point can buffer messages while an end station sleeps)

compared to wireless phones

• smaller cell diameter so lower power transmitters
• no need for wide coverage, instead designated "hot spots" are okay
• data transmission can tolerate lower quality reception (packet delays and retransmisions are okay)
• hand-off from cell-to-cell not as challenging (cf. cell phone in moving car)

in practice, get 1/3 of rated speed

<\ Clemson: Wireless network basics

standards

• 802.11 wireless LANs - called "Wi-Fi" (wireless fidelity)
  • 802.11a - rates up to 54 Mbps using the 5 GHz radio band, range of 20 meters

  • 802.11b - rates up to 11 Mbps using the 2.4 GHz radio band, range of 100 meters (not compatible with 802.11a)

  • 802.11g - rates up to 54 Mbps using the 2.4 GHz radio band, range of 50 meters (speed upgrade of 802.11b)

  • "Super-G" - rates up to 108 Mbps

    (5 GHz is not as crowded with other devices like cordless phones, but 802.11a devices are more expensive than 802.11b/g devices)

• 802.15 personal area network - called "Bluetooth" rates of 1-2 Mbps on 2.4 GHz radio band, range of 100 meters

• 802.16 broadband wireless - called "WiMax" for Worldwide Interoperability for Microwave Access
  • 802.16a - rates up to 70 Mbps over 30 miles, in 2-11 GHz range

  (also called BWA = broadband wireless access)

WAP (wireless application protocol)

• open standard maintained by WAP Forum
• specifically for wireless portable devices with small screens

wireless security

• study on eavesdropping at wi-fi hot spots
• should disable file-sharing on laptops and install a firewall
• can hide SSID (shared set id) of access point
• can register the MAC of NIC cards of valid users (but a valid MAC can be sniffed and spoofed)
• password authentication
• WEP (Wired Equivalent Privacy) - shared key encryption (but Cheswick, Bellovin & Rubin recommend against it)
• WTLS (Wireless Transport Layer Security) - an SSL-like security protocol
• WPA (Wireless Protected Access)

• Intel: Configuring wireless security
• Clemson: Wireless security

[CPSC 330 homepage]

mark@cs.clemson.edu