2b_Mod_

2b_Mod_ - 1 LAB 2 (2) Signal Modulation Introduction Data...

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Unformatted text preview: 1 LAB 2 (2) Signal Modulation Introduction Data Encoding and Signal Modulation Advantages of Signal Modulation Amplitude Modulation Amplitude Modulation of Digital Signals Reducing Power and Bandwidth of AM Signals Frequency Modulation Power and Bandwidth of FM Signals Conclusion 2 Introduction A network and transport layers basic services comprise the end-to-end transport of the bit streams over a set of routers (switches). They are produced using six basic mechanisms: a. Multiplexing b. Switching c. Error control d. flow control e. congestion control f. and resource allocation . 3 Multiplexing Combines data streams of many such users into one large bandwidth stream for long duration. Users can share communication medium. a. Switch b. Multiplexer/Demultiplexer a. Fully connected network b. network with shared links. 4 Data Encoding is: The process of preparing data for efficient and accurate transmission. Analog-to-digital conversion. The conversion process will not change the information contained in the analog data. Once the data is in digital form, it can be encoded as a sequence of voltage levels. Signal Modulation is: The process of encoding a baseband (data) , source signal S m (t) onto a carrier signal. The carrier waveform is varied in a manner related to the baseband signal. The carrier can be a sinusoidal signal or a pulse signal. The result of modulating the carrier signal is called the modulated signal. 5 Signal Modulation S c ( t ) = A cos ( 2 f t+ ) A . Amplitude Modulation (AM), or Amplitude Shift Keying (ASK): The amplitude A of the carrier signal changes in proportion to the baseband signal. B . Phase Modulation (PM), or Phase Shift Keying (PSK): The phase of the carrier signal changes in proportion to the baseband signal. C. Frequency Modulation (FM), or Frequency Shift Keying (FSK): The frequency f of the carrier changes 6 Amplitude , Phase , and Frequency Modulation of a digital baseband signal A M 1 0 0 0 1 0 1 1 0 0 P M 1 0 0 0 1 0 1 1 0 0 F M 1 0 0 0 1 0 1 1 0 0 7 Advantages of Signal Modulation FDM WDM Radio transmission of the signal. m 10 3 s 1 1000 s m 10 3 ; s 1 1000 5 8 = = = = f c f Sc ( t ) = A cos ( 2 fc ) range (fc + f) and (fc - f) . m 30 s 1 10 10 s m 10 3 ; s 1 10 10 6 8 6 = = = = f c f 5GHz 6 cm 8 FDM Original Signals M S c1 ( t ) S m1 ( t ) M S c2 ( t ) S m2 ( t ) M S c3 ( t ) S m3 ( t ) DM S c1 ( t ) DM S c2 ( t ) DM S c3 ( t ) Received Signals S m1 ( t ) S m2 ( t ) S m3 ( t ) Transmission Line Guard band f fc 1- fm 1 fc 1 fc 1 + fm 1 fc 2- fm 2 fc 2 fc 2 + fm 2 ....................... 9 Amplitude Modulation AM is simply the multiplication of the baseband signal with the carrier signal....
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2b_Mod_ - 1 LAB 2 (2) Signal Modulation Introduction Data...

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