CSE3213_05_AnalogDigitalTransmissionW2012_Part_4

CSE3213_05_AnalogDigitalTransmissionW2012_Part_4 -...

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16 ratio of the power in the desired signal to the power in the superimposed noise high SNR high-quality signal & low number of required amplifiers / repeaters Transmission Impairments: Noise (cont.) Signal to Noise Ratio (SNR) SNR (dB) = 10 log 10 SNR power noise average power signal average SNR
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17 Analog Transmission Analog Long-Distance Communications each repeater attempts to restore analog signal to its original form restoration (noise removal) is imperfect noise gets amplified too ! if signal only had components in certain freq. band, repeater could remove noise components outside signal band – but, not those inside signal quality decreases with # of repeaters communications is distance-limited analogy: copy a song using cassette recorder Attenuated and distorted signal + noise Equalizer Recovered signal + residual noise Repeater Amp Goals: 1) restore amplitude 2) remove delay distortion 3) remove noise
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18
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19 Digital Transmission Digital Long-Distance Communications
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Unformatted text preview: regenerator does not need to completely recover the original shape of the transmitted signal it only needs to determine whether the original pulse was positive or negative original signal can be completely recovered each time communication over very long distance is possible analogy: copy an MP3 file compensate for distortion introduced by the channel keep track of intervals that define each pulse sample signal at midpoint of each pulse to determine its polarity Amplifier equalizer Timing recovery Decision circuit and signal regenerator 20 Example [ transmission impairments in digital transmission ] Digital Transmission (cont.) Digital transmission can easily recover from various types of channel impairments. So, is digital transmission the ultimate winner?! 0 1 0.5...
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CSE3213_05_AnalogDigitalTransmissionW2012_Part_4 -...

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