Frequently-Depended Propagation Problem Some Problems are Frequency-Dependent Higher-frequency signals attenuate faster Absorbed more rapidly by water in the air Higher-frequency signals blocked more by obstacles At lower frequencies, signal refract(bend) around obstacles like an ocean wave hitting a buoy At higher frequencies, signals do not refract; leave a complete shadow behind obstacles 5-16
5-16 Frequently-Depended Propagation Problem • Some Problems are Frequency-Dependent – Higher-frequency signals attenuate faster • Absorbed more rapidly by water in the air – Higher-frequency signals blocked more by obstacles • At lower frequencies, signal refract (bend) around obstacles like an ocean wave hitting a buoy • At higher frequencies, signals do not refract; leave a complete shadow behind obstacles
Test Your understanding Page 241 Which of the following has faster attenuation with distance? UTP abc Radio transmission Both have about equally fast attenuation 6 c)e)tg h) 5-17
5-17 Test Your understanding • Page 241 • Which of the following has faster attenuation with distance? – a. UTP. – b. Radio transmission. – c. Both have about equally fast attenuation. • 6 c) e) f) g) h)
Which of the following increases with frequency? -a EMI bcd Multipath interference Both of the above Neither a nor b 5-18
5-18 • Which of the following increases with frequency? – a. EMI. – b. Multipath interference. – c. Both of the above. – d. Neither a. nor b
Figure 5-8: The Frequency Spectrum, Service Bands, and channels F requency Spectrum Signals in different channels do not interfere with one another (0 HZ to Infinity) 3. Channel 5. signal A Multiple Service Channel 4, Signal d Channels Band within a (FM Radio, Channel 3, Signal B Service Cellular Band: each Telephony, Channel 2, No signal Channel etc.) carries a Channel 1, signal e different signal 0 Hz 5-19
5-19 Figure 5-8: The Frequency Spectrum, Service Bands, and Channels Channel 5, Signal A Channel 1, Signal E Channel 2, No Signal Channel 3, Signal B Channel 4, Signal D 0 Hz 2. Service Band (FM Radio, Cellular Telephony, etc.) 1. Frequency Spectrum (0 Hz to Infinity) 3. Multiple Channels within a Service Band; each Channel carries a different signal 4. Signals in different channels do not interfere with one another
Figure 5-9: Channel Bandwidth and Transmission Speed study Figure) Signal Bandwidth Chapter 3 discussed a wave operating at a single frequency However, most signals are spread over a range of frequencies The higher the speed, the greater the spread of frequencies Amplitude Signal Frequency 5-20
5-20 Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) • Signal Bandwidth – Chapter 3 discussed a wave operating at a single frequency – However, most signals are spread over a range of frequencies – The higher the speed, the greater the spread of frequencies Amplitude Frequency Signal