EEN404_09fall_final_key

EEN404_09fall_final_key - EEN 404 — Communication Systems...

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Unformatted text preview: EEN 404 — Communication Systems — Fall 2009 1 Final Exam — December 8, 2009 Closed book, close note, but a cheat sheet of letter size is allowed. Please be rigorous and precise; show your work to get points. NAME: STUDENT ID: GOOD LUCK! EEN 404 — Communication Systems — Fall 2009 Total points: 100 Duration: 2.5 hours Problem Score 1 (15pts) 6 (20pts) Total (100pts) EEN 404 — Communication Systems — Fall 2009 3 1. (15 points) Given the random binary sequence 0110, provide waveform sketches for a) NRZ Change, b) split phase, and c) unipolar RZ EEN 404 — Communication Systems — Fall 2009 4 t—4T 2. (15 points) A message signal is given by m(t) = 21K? sampled with a sampling period equal to T. ) — 1. The message signal is (a) If the message samples are transmitted using PAM with a pulse width 7‘ = T/4, determine and sketch the transmitted signals in the interval 0 S t 3 4T. (13) If the message samples are transmitted using PWM with a unit amplitude, deter— mine and sketch the transmitted signals in the interval 0 g t 3 4T. (0) If the message samples are transmitted using PPM with a unit amplitude, deter— mine and sketch the transmitted signals in the interval 0 g t 3 4T. EEN 404 — Communication Systems — Fall 2009 \m f‘ ,. § ’“ “'4 ‘W‘ “4' 4M”? <~ Mu possh‘m ' W) D 7.17 51 41mm EEN 404 — Communication Systems — Fall 2009 6 3. (20 points) (a) Describe Nyquit’s criterion for zero intersymbol interference. Suppose the channel bandwidth is W. What is the maximum data rate for a binary digital transmission system Without 181? What is the maximum data rate if 8—ary PAM is employed ? (b) Sketch the following spectra EU) 2 —A(%) and P2(f) = +A(%). Tell which ones satisfy Nyquist’s criterion. For those that do, ﬁnd the appropriate sample interval, T, in terms of W, and the corresponding pulse shape function COW MAW 9109"}?1' (“(7’) hc Cw 9' I’LKC‘P) 4‘ t 4* v1 TWWW claw..qu maﬁa \ x x a b‘\nu(\ Mm.$§‘ml MQX'MUBM W \ ‘3 aw/ Fm, 8»o«>/ QAM, maﬁa/mm clock Ma— l; 13an “~16ij (b) 7—7—19 Zem 151 .. w A. W K Cg Tr“) 44"” Emprf'f‘F? “Q :3 zero 1m ?1C+) 7.: QWS¥‘<’\C(9~W‘(~> «him/$.54 (CW-(781‘ EEN 404 — Communication Systems — Fall 2009 8 4. (15 points) In an AM system, the bandwidth of the bandpass predetection ﬁlter is BT = 2W and the bandwidth of the lowpass postdetection ﬁlter is BD 2 3W, where W is the bandwidth of the message signal. (a) Determine SNR at the input of the postdetection ﬁlter (b) Determine SNR at the output of the postdetection ﬁlter (0) Determine the detection gain. PD?) Pfemmx ‘6“) Pas.“~ 3M «f: \m v Kicker 3 DCJ’ JWQWe—t J ) Ac, ((+0. WW3 CVSCwo+3+RZ+ 3 WW 4‘ 5t“: WW 2 WWW (2.1%? «(a 8w: 6!. 54:“ "1' aﬁcCl+a<mfm>J [950—130 “3.”, 3w “03¢ 30% UK... 3 f r (0‘) SW 3 is a ACTH“? t a l "300) W ([0 ) 390+); Ac. CUYMH) + Vic c—e ) 5.2m PSDzv “ Q F‘JW SHED : A:O\2CM:}”> ‘3 as“? “He 8W M M; xgw EEN 404 — Communication Systems — Fall 2009 9 5. (15pts) (a) Suppose the data rate of a digital transmission system With BPSK (with m = 0) modulation is R = 10 Kbps and the power spectral density of the additive White Gaussian noise is NO / 2 = 10—6 / 2 W/HZ. Find the required power to give a bit error probability of 10—5. (b) In the system described in (a), if modulation method is changed to ASK and other parameters remain the same, ﬁnd the required power to give a bit error probability of 10—5. 2. .. ~S‘ (CD PE. “®( A r) 0(1)»?40 mam-24,26 Ma, 2 W T “R :2 (0 4‘ Tatq~¢ l EEN 404 — Communication Systems — Fall 2009 10 6. (20pts) A digital communication system transmits signal 31(t) for bit “1” and 52(t) for bit “0”. 81(t) and 52(t) are shown in the ﬁgure below. (a) Sketch the impulse response of the matcher ﬁlter for 81(t) and 82 (t) (b) Find the energy per bit E, (0) Determine the optimum threshold used by the receiver to make a decision ( ) ) (1 Give an expression for error probability in terms of A, T, to and N0. (e Determine the value of to that minimizes error probability. SH" ) EEN 404 — Communication Systems — Fall 2009 11 (oh 3 C. w T. "is? (5%“); (329)“Sxmde =5: "‘ T ,. a m W “@(W “GE-6e; in 2N6 Ala-r23») (is (MW/u up 2% ‘ when 4% a. 3!: r “(ﬁg/Mu‘m‘w PE L; LJ‘UM ﬁrs—L L63) ...
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This note was uploaded on 10/28/2010 for the course EEN 404 taught by Professor X.cai during the Spring '10 term at University of Miami.

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EEN404_09fall_final_key - EEN 404 — Communication Systems...

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