Wireless Technology

1. 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 • 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 • responsible for preventing/controlling interference by devices • Divides EM spectrum for control • AM radio highly susceptible to RI • ISM band • 902-928Mhz, 2.4-2.48GHz, & 5.725-5.85GHz • industrial scientific and medical devices

7. Antenna • Omni • Dipole • Yagi • Flat Panel • Parabolic

8. Radio Waves • Frequency • 10kHz • 3,000,000 MHz (3 THz) • Longer wavelength infrared/microwave • Networking • 802.11 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) •  a method of encoding digital data on multiple carrier frequencies • used in applications such as digital television and audio broadcasting • OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal. 

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 • 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 802.11a

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 802.11b

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 • 802.15 WPAN / PAN • Wireless Personal Network • 802.16 BWA • Broadband Wireless Access • Currently a hodgepodge of proprietary standards

22. 802.15 PAN / WPAN 802.15.1 Bluetooth 802.15.2 Sharing 2.4GHz with 802.11 802.15.3 High Speed PAN (10m) 802.15.4 Low Speed PAN ZigBee fits under 802.15.4

23. USB wireless and Bluetooth USB Wireless • 3m at 480Mbps • 10m at 100Mbps Bluetooth - wattage determines range • 2.4 GHz but non interfering with 802.11b. • 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 802.11 • 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 • 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 • 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 • personal and enterprise mode • 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.