Wired and wireless Frequency spectrum Spectrum & Bandwidth Lesson 1 Wired and wireless Frequency spectrum

Spectrum & Bandwidth Spectrum Absolute bandwidth Effective bandwidth range of frequencies contained in signal Absolute bandwidth width of spectrum Effective bandwidth Often just bandwidth Narrow band of frequencies containing most of the energy

EM Spectrum    ISM band 902 – 928 Mhz 2.4 – 2.4835 Ghz 5.725 – 5.785 Ghz ISM band AM radio S/W radio FM radio TV TV cellular LF HF VHF UHF SHF EHF MF   30kHz 300kHz 3MHz 30MHz 300MHz 30GHz 300GHz 10km 1km 100m 10m 1m 10cm 1cm 100mm 3GHz X rays Gamma rays  infrared visible UV 1 kHz 1 MHz 1 GHz 1 THz 1 PHz 1 EHz Propagation characteristics are different in each frequency band

Wireless LANs (CSMA/CA) IEEE 802.11 Bandwidth: 1 or 2 Mbps 802.11b - 11 Mbps (2.4 GHz) 802.11g - 54 Mbps (2.4 GHz) 802.11a - 54 Mbps (5 GHz) Physical Media spread spectrum radio (2.4 GHz) diffused infrared (10 m) Wireless LAN irDA Bluetooth

Wireless LANs (CSMA/CA) IEEE 802.11 Bandwidth: 1 or 2 Mbps 802.11b - 11 Mbps (2.4 GHz) 802.11g - 54 Mbps (2.4 GHz) 802.11a - 54 Mbps (5 GHz) Physical Media spread spectrum radio (2.4 GHz) diffused infrared (10 m) Wireless LAN irDA Bluetooth

Unlicensed Radio Spectrum  33cm 12cm 5cm 26 Mhz 83.5 Mhz 125 Mhz 902 Mhz 2.4 Ghz 5.725 Ghz 928 Mhz 2.4835 Ghz 5.785 Ghz cordless phones baby monitors Wireless LANs 802.11 Bluetooth Microwave oven 802.11a Pravin Bhagwat @ AT&T Labs

802.11 Wireless LANs 802.11b Standard for 2.4GHz ISM band (80 MHz) DSSS, 1.6 Mbps, 500 ft range Star or peer-to-peer architecture 802.11a Standard for 5GHz NII band (300 MHz) OFDM with time division 20-70 Mbps (adapt. modulation/coding), variable range Aloha access, Peer-to-peer architecture 802.11g Same as 802.11a but in the 2.4 GHz ISM band 802.11n, 802.11e Standards being developed to include MIMO or QoS

Other Wireless Networks 3G Cellular mobile Uses CDMA; 2Mb/s indoor, 384kb/s outdoor. Technology developed and deployed. Spectrum auctioned at over $1,000 per subscriber. Some think this will make it too expensive. Bluetooth For short-range communication within a small system. E.g.: headset to cell-phone; computer to printer. Uses 2.45GHz unlicensed spectrum and frequency-hopping. Up to 721kb/s data rate and about 10m.

Data Analog Digital Continuous values within some interval e.g. sound, video Digital Discrete values e.g. text, integers

Analog Transmission Analog signal transmitted without regard to content May be analog or digital data Attenuated over distance Use amplifiers to boost signal Also amplifies noise

Digital Transmission Concerned with content Integrity endangered by noise, attenuation etc. Repeaters used Repeater receives signal Extracts bit pattern Retransmits Attenuation is overcome Noise is not amplified

Acoustic Spectrum (Analog)

Signals Means by which data are propagated Analog Digital Continuously variable Various media wire, fiber optic, space Speech bandwidth 100Hz to 7kHz Telephone bandwidth 300Hz to 3400Hz Video bandwidth 4MHz Digital Use two DC components

Data and Signals Usually use digital signals for digital data and analog signals for analog data Can use analog signal to carry digital data Modem Can use digital signal to carry analog data Compact Disc audio

Analog Signals Carrying Analog and Digital Data

Digital Signals Carrying Analog and Digital Data

Advantages of Digital Transmission Digital technology Low cost LSI/VLSI technology Data integrity Longer distances over lower quality lines Capacity utilization High bandwidth links economical High degree of multiplexing easier with digital techniques Security & Privacy Encryption Integration Can treat analog and digital data similarly