Year Event 1838 Morse demonstrates telegraph 1864 Maxwell

通訊技術的演變歷史 Year Event 1838 Morse demonstrates telegraph 1864 Maxwell predicts electromagnetic radiation 1876 Bell patents the telephone 1897 Marconi patents a complete wireless telegraph system 1915 Bell System completes a transcontinental telephone line 1938 Television broadcasting begin WWII Radar and microwave systems are developed 1948 The transistor is invented; Shannon’s “A Mathematical Theory of Communications, ” is published

通訊技術的演變 (continued) 1956 First tranoceanic telephone cable 1962 First communication satellite, Telstar I, is launched. First live television coverage of moon exploration. 1970 Color TV 1980 s First generation cellular radio systems (Analog): AMPS (US and Canada), NMT (Scandinavia) 1990 s Second generation cellular radio systems (Digital): IS 95 (US and Canada), GSM (Europe) 1995+ Bluetooth, Wireless LAN, Cable modem, x. DSL 2000 Third generation cellular radio systems (CDMA): CDMA 2000 (US and Canada), WCDMA (Europe) 2000+ DAB, DVB, HDTV, The 4 th generation radio communications

Evolution of Cellular Mobile Communications 1 G 2 G AMPS D-AMPS ETACS 2. 5 G 3 G UWC-136 IS-95 A IS-95 B cdma 2000 GSM GPRS WCDMA PDC TD-SCDMA

GSM Evolutionary Concept Capabilities Downward Compatibility IMT-2000 Phase 1 Phase 2+ Phase 2 Phase 1 1995 1997 Speech FR, Basic Services Data: 0. 3 - 9. 6 kbit/s Supplementary Services (SS) ® ISDN Decision: Downward Compatibility • New Services • IN-applications • high data rates • special services for Closed User Groups UMTS W-CDMA etc. Year

Selected Radio Frequency Bands Use Frequency Omega Navigation 3 -30 KHz Loran C Navigation 30 -300 KHz AM broadcast 540 -1600 KHz FM broadcast 88 -108 MHz TV 54 -72, 76 -88, 174 -216, 420 -890 MHz AMPS (Advanced Mobile Phone System) 869 -894 (downlink), 824 -849 (uplink) MHz GSM (Global System of Mobile Radio) 890 -915 (downlink), 935 -960 (uplink) MHz Unlicensed Bands 2. 4 -2. 4835, 5. 15 -5. 35, 5. 725 -5. 825 GHz

Frequency Spectrum • The most precious resource in communications is “frequency spectrum” • The “frequency spectrum” has to be shared by a large number of users and applications: • AM Radio, FM Radio, TV, cellular telephony, wireless local-area-networks, satellite, air traffic control

Transmit Spectrum

Allocated Channels

Noise • Internal and External Noise • Internal Noise: Generated by components within a communication system (thermal noise) • External Noise: – Atmospheric noise (electrical discharges) – Man-made noise (ignition noise) – Interference (multiple transmission paths)

通道效應 Multipath Fading t 2 t 1 0 t 3 t 1 t 2 t 3

Analog Vs Digital (Advantages and Disadvantages) Digital Comm. System Analog Comm. System Advantages: Disadvantages: • Inexpensive • Privacy preserved (Data encryp. ) • Can merge different data • Error correction • Expensive • No privacy preserved • Cannot merge different data • No error correction capability Disadvantages: Advantages: • Larger bandwidth • Synchronization problem is relatively difficult. • Smaller bandwidth • Synchronization problem is relatively easier.