08-IntroductionToDigitalModulation

08-IntroductionToDigitalModulation - Digital Communication...

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Introduction to Digital Modulation Instructor: M.A. Ingram ECE4823 Digital Communication Transmitter User Interface Encoder Modulator RF Front End antenna bits 0110 more bits 011001 waveforms (symbols) Frequency up-conversion and amplification ± A simplified block diagram: interleaver Digital Communications Receiver ± A simplified block diagram: User Interface Decoder Demodulator RF Front End antenna bits 0110 “soft detections” of coded bits 011001 waveforms (faded symbols plus noise) Low-noise amplification and frequency down-conversion deinterleaver Symbols ± In each symbol period, T s , a digital modulator maps N coded bits word to a transmitted waveform from a set of M=2 N possible waveforms ± Each waveform corresponds to an information symbol, x n ± For Binary symbols, N=1 Detection ± The job of the receiver is to determine which symbols were sent and to reconstruct the bit stream that created them Definitions ± Bit Rate (bits per sec or bps) ± Bandwidth Efficiency (bps/Hz) where B is the bandwidth occupied by the signal S T N R / = B R B / = η
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Shannon Theorem ± In a non-fading channel, the maximum bandwidth efficiency, or Shannon Capacity is SNR = signal-to-noise ratio () SNR MAX B + = 1 log 2 η Pulses ± A symbol period, T s , suggests a localization in time ± Localization in frequency is also
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This note was uploaded on 01/20/2012 for the course EE 301 taught by Professor Ahmetçakar during the Spring '11 term at Gazi Üniversitesi.

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08-IntroductionToDigitalModulation - Digital Communication...

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