In Figure 2(a) the block diagram of a baseband communication system is presented. In this system....

 

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In Figure 2(a) the block diagram of a baseband communication system is presented. In this system. M =4 level equiprobable information sysmbols a, e {F1,F3} are transmitted with signals s; (t), i=1,2,3,4. Modulation interval is 7 = 12 ms. Transmit filter transfer function G, (f) is selected as "root raised cosine (RRC)" with roll-off factor a and receive filter is matched to gr(t) = ¹ {G, (f)}. Also channel transfer function C(f) is given in Figure 2(b). Channel noise is zero mean, additive White Gaussian noise (AWGN) with two sided power specral density No/2. In the receiver side, channel equalization methods are ignored. nw (t) r(KT) m(t) y(t) Channel Transmitter Filter GT (f) Decision Receiver Filter (+) Decision Circuit C(f) Σa, 8(t-nT) GR(f) Figure 2(a) C(f) 0.5 -150 -100 -50 0 50 100 150 f(Hz) Figure 2(b) a) What is the maximum value of a wich can provide a system without intersymbol interference (ISI)? For a convenient value of a, which provides a system without ISI, compute the bandwidth efficiency. If the number of levels (M) is doubled and modulation interval (T) is halved, what will be the bandwidth efficiency? Please explain. b) Please express the probable signals transmitted from transmitter s; (t), i=1,2,3,4 and xc (t), in terms of gr(t) where xe(t) = Σan gr(t-nT). Sketch x(t) signal for an information sequence a, (+1, +1, -3, +3). c) For this system, in the absence ISI and noise, obtain r(kT) values at the input of decision device. Sketch r(t) for a, (+1, +1.-3. +3) information sequence. = d) For a = +3 and N₁ /2=10¹ W/Hz, compute SNR at the input of the decision device. t = kT In Figure 2(a) the block diagram of a baseband communication system is presented. In this system. M =4 level equiprobable information sysmbols a, e {F1,F3} are transmitted with signals s; (t), i=1,2,3,4. Modulation interval is 7 = 12 ms. Transmit filter transfer function G, (f) is selected as "root raised cosine (RRC)" with roll-off factor a and receive filter is matched to gr(t) = ¹ {G, (f)}. Also channel transfer function C(f) is given in Figure 2(b). Channel noise is zero mean, additive White Gaussian noise (AWGN) with two sided power specral density No/2. In the receiver side, channel equalization methods are ignored. nw (t) r(KT) m(t) y(t) Channel Transmitter Filter GT (f) Decision Receiver Filter (+) Decision Circuit C(f) Σa, 8(t-nT) GR(f) Figure 2(a) C(f) 0.5 -150 -100 -50 0 50 100 150 f(Hz) Figure 2(b) a) What is the maximum value of a wich can provide a system without intersymbol interference (ISI)? For a convenient value of a, which provides a system without ISI, compute the bandwidth efficiency. If the number of levels (M) is doubled and modulation interval (T) is halved, what will be the bandwidth efficiency? Please explain. b) Please express the probable signals transmitted from transmitter s; (t), i=1,2,3,4 and xc (t), in terms of gr(t) where xe(t) = Σan gr(t-nT). Sketch x(t) signal for an information sequence a, (+1, +1, -3, +3). c) For this system, in the absence ISI and noise, obtain r(kT) values at the input of decision device. Sketch r(t) for a, (+1, +1.-3. +3) information sequence. = d) For a = +3 and N₁ /2=10¹ W/Hz, compute SNR at the input of the decision device. t = kT

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