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PowerPoint PresentationTerrestrial (wireless) Broadcast Technologies and ApplicationsA Quick Review...A Quick Review (cont’d)...Slide 5NTSC SignalVSB ModulationHDTVSqueezing HDTV into 6MHz ChannelsLMDSSlide 11DBSSatellite PagingCopyright 2002, S.D. Personick. All Rights Reserved. 1Telecommunications Networking II Topic 13Broadcast Technology and ApplicationsDr. Stewart D. PersonickDrexel UniversityCopyright 2002, S.D. Personick. All Rights Reserved. 2Terrestrial (wireless) Broadcast Technologies and Applications•AM and FM radio•Conventional Analog Television•HDTV•LMDS (Local Multipoint Distribution Service)•DBS•PagingCopyright 2002, S.D. Personick. All Rights Reserved. 3A Quick Review...•AM Radio (medium frequency / high frequency ~1-5 MHz) -Amplitude Modulation: [1 + m(t)] cos (2ft)-High Power Transmitter > 1 kW= +60 dBm-Large transmitter antenna: ~300 meters (@ 1 MHz)-Thermal-Noise-Limited Receiver Sensitivity: ~kT x 10kHz x [~40dB = 10**4] = ~ 4 x 10**-13 watts = -94 dBm -Issues: static, small receiver antenna, absorption, multi-path fading, no line of sight ...Copyright 2002, S.D. Personick. All Rights Reserved. 4A Quick Review (cont’d)...•FM Radio (very high frequency ~ 100 MHz) -FM modulation: A cos[ m(u)du + 2ft]-Transmitter power > 1kW= +60dBm-Small transmitter antenna: ~3 meters-Thermal-Noise-Limited Receiver Sensitivity: kT x 100 kHz x [~40dB = 10**4]= ~ 4 x 10**-12 = -84 dBm- Issues: signal blockage, multi-path fading Copyright 2002, S.D. Personick. All Rights Reserved. 5A Quick Review (cont’d)...•NTSC Television -Transmitter power > 1kW= +60 dBm-VSB modulation for B&W video information, plus sub-carriers for color (QAM) and audio information (FM) -Bandwidth = 6MHz- Required SNR ~ 43 dB- kT x 6MHz x 20,000 ~ 4.8 x 10**- 10 watts ~ -63 dBmCopyright 2002, S.D. Personick. All Rights Reserved. 6NTSC SignalHorizontal “sync tip”Black levelWhite level1 volt0.4 volt1/[525x30] secondsCopyright 2002, S.D. Personick. All Rights Reserved. 7VSB Modulationf(MHz)-4.535 0 4.535Baseband Spectrum f1-0.75 f1 f1+4.535Lower sideband removedf1-1.25Copyright 2002, S.D. Personick. All Rights Reserved. 8HDTVWide Screen: 16 x 9 Aspect Ratio v. 4 x 3 for NTSC~1100 lines per frame vs. 525 for NTSC~ 5 x the amount of available information vs. NTSC~30 MHz bandwidth in analog form x 3 colorsEquivalent bit rate (no compression) ~2 x 30 x 10**6 (samples/sec) x 3 (colors) x 1 byte/sample-color x 8 bits/byte = 1.44Gbps !!!Copyright 2002, S.D. Personick. All Rights Reserved. 9Squeezing HDTV into 6MHz Channels•6 MHz x 4-8 bits per second/Hz = 24-48 Mbps•Need ~ a factor of 30-60 of compression•Observation: If you can squeeze 1 HDTV channel into 6MHz, then you can squeeze 5 digital NTSC quality signals into 6 MHz!Copyright 2002, S.D. Personick. All Rights Reserved. 10LMDS1-5 kmRF~28 GHzB~ 1GHzCopyright 2002, S.D. Personick. All Rights Reserved. 11LMDS•Local Multipoint Distribution Service•Operates at approximately 28 GHz with ~ 1GHz of bandwidth available (combined downstream toward end users and upstream toward the base station). ~ 1-5 km reach•Very much like a wireless version of an upgraded coaxial cable system•Coverage is a critical limitationCopyright 2002, S.D. Personick. All Rights Reserved. 12DBS•Direct Broadcast Satellite•10 GHz, ~150 channels of digital TV or other data•NTSC quality digital TV requires ~ 1MHz of bandwidth, ~26 dB SNR (or greater)•Limited by rain attenuation, line-of-site to satellite, receiver dish size, and transmitter outputCopyright 2002, S.D. Personick. All Rights Reserved. 13Satellite Paging•Example: 1 million customers (pagers) @ 1 page per hour x 256 bytes per page =256 Mbyte/hr = 0.57 Mbps•Thermal-noise-limited receiver power ~kT x 570,000 x SNR (~36) ~ 10**-13 W•Transmitter (on satellite) >100 W•Allowable loss ~150 dB•If spot radius = 1000km, then ant. equiv. radius must be ~ 3.1


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