CSE3213_07_ShiftKeyingW2012_Part_4

CSE3213_07_ShiftKeyingW2012_Part_4 - 16 Example What are...

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16 Example [ What are supported R[bps] in ASK/PSK systems? ] W [Hz] W [Hz] W [Hz] W [Hz] Ch 1 Freq. Ch 2 Ch 3 Ch 4 PSK- based system What is the maximum data-rate (R [bps]) offered to each device?
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17 Modulation of Digital Data: PSK (cont.) B f c +B f f f c -B f c If bandpass channel has bandwidth W c [Hz], then baseband channel has W c /2 [Hz] available, so modulation system supports 2*( W c /2) = W c [pulses/second] recall Nyqyist Law: baseband transmission system of bandwidth W c [Hz] can theoretically support 2 W c pulses/sec Facts from Modulation Theory W c W c /2 Baseband signal x(t) with bandwidth W c /2 If then Modulated signal x(t) cos(2 f c t ) has bandwidth W c Hz How can we recover the factor 2 in supported data-rate !? Data rate = 2*W c /2 = B [bps]
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18 Modulation of Digital Data: PSK (cont.) QPSK = 4-PSK PSK that uses phase shifts of 90º= /2 rad 4 different signals generated, each representing 2 bits advantage : higher data rate than in PSK (2 bits per bit
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This note was uploaded on 02/14/2012 for the course CSE 3213 taught by Professor A during the Winter '10 term at York University.

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CSE3213_07_ShiftKeyingW2012_Part_4 - 16 Example What are...

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