1. Networking Fundamentals
Wireless Technology
Networking Fundamentals

2. Electromagnetic Waves
Radio Waves
AM 500kHz
FM MHz
Satellite upto 22GHz
Microwaves
Micro refers to the wavelength (um)

3. Transmission Carrier Wave
set Frequency
carries data
higher frequency than signal
Modulation - mixing of carrier wave and data signal
Transmitter - modulates signal
Receiver - demodulates signal

4. and Receiving Demodulation Channel Voice bandwidth
FM radio has 200kHz Channels (FCC assigned)
Voice
400Hz - 4Khz
Barely distorts the carrier wave

5. Infrared TV remote Digital on-off light signal
Line of sight (but bounces)
requires aim
short distances (unless lasers used)
Dispersion controlled with lenses
1-2 Mbps
Higher rates possible with lasers

6. Radio Interference FCC AM radio highly susceptible to RI ISM band
responsible for preventing/controlling interference by devices
Divides EM spectrum for control
AM radio highly susceptible to RI
ISM band
Mhz, GHz, & GHz
industrial scientific and medical devices

7. Antenna
Omni
Dipole
Yagi
Flat Panel
Parabolic

8. Radio Waves Frequency Longer wavelength infrared/microwave Networking
10kHz
3,000,000 MHz (3 THz)
Longer wavelength infrared/microwave
Networking
and Bluetooth
specifies 2.4GHz

9. RW Transmission Techniques
Single Frequency
Spread Spectrum
Orthogonal Frequency-Division Multiplexing

10. Spread Spectrum Multiple channels spread across the bandwidth spectrum
frequency hopping - simultaneous
direct sequencing - sequential

11. FHSS data packets skip channels some channels may have interference
limited data rate
divides 2.4GHz band (bandwidth 83.5Mhz) into 79 1Mhz Channels

12. DSSS 11 83Mhz channels 3 subchannels of 22MHz at 11Mbps
can achieve 33 Mbps in parallel

13. OFDM 5GHz band at 54Mbps Classified U-NII 1/2/3 100Mhz each
4 20 Mhz channels for each class
52 300k0Hz subchannels (48 data, 4 ec)

14. Wireless Access Points (WAP)
Connects wireless to cable network
Two omni antennae
Service Set ID (SSID)
shared by Multiple Access Points (ESSID)
Encryption slows the network
provides some security
Independent Basic Service Set - no AP
adhoc networking between wireless devices

15. 802.11a 5GHz 54,48,36,24,18,12,9,or 6 Mbps short range
penetration issues
54,48,36,24,18,12,9,or 6 Mbps

16. 802.11b adopted before 802.11a 11, 5.5, 2, or 1Mbps
11 channels to select from
2.4GHz doesn’t interfere with a

17. 802.11g 2.4GHz (not compatible with 802.11a) compatible with 802.11b
54Mbps
48, 36, 28, 24, or 12Mbps
11, 9, 6, 5.5, 2, or 1Mbps
Shorter range than b

18. 802.11n 5Ghz but compatible with 2.4Ghz compatible with 802.11 a,b & g
MIMO technology is spatial multiplexing
multiple data streams
will eventually allow 600Mbps or higher

19. 802.11 Access Method CSMA/CA CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance
Listen, if quiet generate RTS
RTS signal -- ready to send
CTS wait for it -- clear to send
NOT CSMA/CD
Carrier Sense Multiple Access with Collision Detection
Wireless device cannot see all devices in range of WAP

20. Collision Detection vs Avoidance
Always possible on Cable segment
2 Wireless devices can be in range of AP and not in range of each other
Cannot detect collisions
Collision occurs at WAP
Other methods of Collision Avoidance exist
token (ring), time slice, channels

21. IEEE Wireless Working Groups
WPAN / PAN
Wireless Personal Network
BWA
Broadband Wireless Access
Currently a hodgepodge of proprietary standards

22. PAN / WPAN
Bluetooth
Sharing 2.4GHz with
High Speed PAN (10m)
Low Speed PAN
ZigBee fits under

23. USB wireless and Bluetooth
3m at 480Mbps
10m at 100Mbps
Bluetooth - wattage determines range
2.4 GHz but non interfering with b.
79 channel FHSS
short range piconet/WPAN
1, 3, 24 Mbps based on standard version 1.0, 2.0, 3.0

24. Cellular Technology
Cells use radio waves to communicate with devices in the cell and microwave to communicate to other cells.

25. Microwave Transmissions
Wavelength 1mm to 30cm
Frequencies 1GHz to 300GHz
includes
Data rates are tied to frequency
higher is better

26. Satellites High Orbit slower than Geosyncronous GeoSynchronous Orbit
22,300 Miles (35,880km) up
68,000 mph
24hr orbit appears stationary
Easy to track
propagation delay (latency) 250 ms (data) or ½ sec (telephone)
controlling jitter via buffering
Low Orbit faster than Geosynchronous
Motorola’s Iridium
66 sats, low propagation delay, $$$$
abandoned

27. Wireless Security There is none There are some measures
signal escapes through glass
cable can be physically secured
War Driving in google street view cars
There are some measures
802.1x Authentication
802.1x Encryption

28. Authentication EAP Extensible Authentication Protocol
PEAP Protected EAP
Computers/Devices are authenticated not users. Password alone not enough to get on the network.

29. Encryption WEP Wired Equivalent Privacy WPA WiFi Protected Access
Network Key
Required by all on network but key never changes
WPA WiFi Protected Access
personal and enterprise mode
Enhanced WEP
TKIP (802.11i) Temporal Key Integrity Protocol, Key changes with time
WPA-PSK Pre-Shared Key
SOHO networks easy setup
passphrase, key changes automatically
WPA-2 Improved WPA
enterprise mode requires 802.1x security server
AES advanced encryption standard
WAP Wireless Application Protocol ensures safe exchange of data between Wireless network and Wi-Fi device. Uses keys to identify and encrypt.