Copyright 2002, S.D. Personick. All Rights Reserved.1 Telecommunications Networking II Topic 13 Broadcast Technology and Applications Dr. Stewart D. Personick Drexel University

Copyright 2002, S.D. Personick. All Rights Reserved.2 Terrestrial (wireless) Broadcast Technologies and Applications AM and FM radio Conventional Analog Television HDTV LMDS (Local Multipoint Distribution Service) DBS Paging

Copyright 2002, S.D. Personick. All Rights Reserved.3 A 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.4 A 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.5 A 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 dBm

Copyright 2002, S.D. Personick. All Rights Reserved.6 NTSC Signal Horizontal “sync tip” Black level White level 1 volt 0.4 volt 1/[525x30] seconds

Copyright 2002, S.D. Personick. All Rights Reserved.7 VSB Modulation f(MHz) Baseband Spectrum f f1 f Lower sideband removed f1-1.25

Copyright 2002, S.D. Personick. All Rights Reserved.8 HDTV Wide 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 colors Equivalent 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.9 Squeezing HDTV into 6MHz Channels 6 MHz x 4-8 bits per second/Hz = Mbps Need ~ a factor of 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.10 LMDS 1-5 km RF~28 GHz B~ 1GHz

Copyright 2002, S.D. Personick. All Rights Reserved.11 LMDS 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 limitation

Copyright 2002, S.D. Personick. All Rights Reserved.12 DBS 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 output

Copyright 2002, S.D. Personick. All Rights Reserved.13 Satellite Paging Example: 1 million customers 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 cm