Networking Fundamentals Wireless Technology Networking Fundamentals

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

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

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

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

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 902-928Mhz, 2.4-2.48GHz, & 5.725-5.85GHz industrial scientific and medical devices

Antenna Omni Dipole Yagi Flat Panel Parabolic

Radio Waves Frequency Longer wavelength infrared/microwave Networking 10kHz 3,000,000 MHz (3 THz) Longer wavelength infrared/microwave Networking 802.11 and Bluetooth specifies 2.4GHz

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

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

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

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

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)

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

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

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

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

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

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

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

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

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

USB wireless and Bluetooth 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

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

Microwave Transmissions Wavelength 1mm to 30cm Frequencies 1GHz to 300GHz includes 802.11 Data rates are tied to frequency higher is better

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

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

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

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.