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Why Interleaving and Recursive Encoding? • In a coded systems: – Performance is dominated by low weight code words. • A “good” code: – will produce low weight outputs with very low probability. • An RSC code: – Produces low weight outputs with fairly low probability. – However, some inputs still cause low weight outputs. • Because of the interleaver: – The probability that both encoders have inputs that cause low weight outputs is very low. – Therefore the parallel concatenation of both encoders will produce a “good” code. Iterative Decoding: • There is one decoder for each elementary encoder. • Each decoder estimates the a posteriori probability (APP) of each data bit. • The APP’s are used as a priori information by the other decoder. • Decoding continues for a set number of iterations. – Performance generally improves from iteration to iteration, but follows a law of diminishing returns The Turbo-Principle: Turbo codes get their name because the decoder uses feedback, like a turbo engine
Performance as a Function of Number of Iterations: 10 0 E b /N o in dB 10 -1 10 -2 1 iteration BER 10 -3 10 -4 6 iterations 2 iterations 3 iterations 10 -5 10 iterations 10 -6 18 iterations 10 -7 0.5 1 1.5 2 Turbo Code Summary: • Turbo code advantages: – Remarkable power efficiency in AWGN and flat-fading channels for moderately low BER. – Deign tradeoffs suitable for delivery of multimedia services. • Turbo code disadvantages: – Long latency.
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DC COURSE FILE
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GEETHANJALI COLLEGE OF ENGINEERING
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Convolution Codes: Encoding, decodi
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III. To inculcate positive attitude
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7. Importance of the course and how
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DC 12: Compute the power and bandwi
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10. Course mapping with PEO’s and
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13.Micro plan : Sl. no Unit No. Tot
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14.Detailed Notes UNIT 1 : Elements
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A communication system may transmit
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the wavelength is extremely long, m
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asic elements of digital communicat
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4. Channel introduced many types of
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5. Bandwidth is another scarce reso
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Pulse Code Modulation ‣ PCM gener
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77777333333333333333333333333333333
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• The most common technique for s
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Pulse Code Modulation (PCM) : • P
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Figure 3.11 Illustration of the qua
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Quantization (nonuniform quantizer)
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Time-Division Multiplexing(TDM):
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Let m n where T The error signal is
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3. Simplify receiver design Because
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Figure 3.27 Block diagram illustrat
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Adaptive Differential Pulse-Code Mo
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ASK, OOK, MASK: • The amplitude (
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Frequency Shift Keying: • One fre
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s t Acos 2f ct 3 Acos 2f
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QAM and QPR: • QAM is a combinati
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Generation and Detection of Coheren
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Figure 6.29 Signal-space diagram fo
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UNIT 3 Base Band Transmission And O
Page 74 and 75: • The tails of hI(t) decay as 1/|
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Page 80 and 81: • Equalization : to compensate fo
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Page 84 and 85: - Flexibility - Same H/W may be tim
Page 86 and 87: Interpretation of Eye Diagram:
Page 88 and 89: The set of source symbols is called
Page 90 and 91: We will usually neglect to mention
Page 92 and 93: Note that if Condition1 is satisfie
Page 94 and 95: where dmin is the minimum Hamming d
Page 96 and 97: Linear Block Codes - example 1: •
Page 98 and 99: • S null can be represented by it
Page 100 and 101: G 1 0 I | P 0 0 0 1 0 0 0 0
Page 102 and 103: • Compared with the systematic co
Page 104 and 105: Convolutional Codes ◊ The encoder
Page 106 and 107: Convolution Codes ‣ Encoding, ‣
Page 108 and 109: x m m ''' j j 2 j Here each messa
Page 110: Representing convolutional codes: C
Page 113 and 114: - encoder state diagram for (n,k,L)
Page 115 and 116: • For this reason the non-survive
Page 117 and 118: sequence is 1 1 0 0 0 0 0 (why?). N
Page 119 and 120: Error Correction: • If there is n
Page 121 and 122: correct:1+1+2+2+2=8;8 ( 0.11) 0.88
Page 123: Motivation: Performance of Turbo Co
Page 127 and 128: General Model of Spread Spectrum Sy
Page 129 and 130: Slow and Fast FHSS: • Frequency s
Page 131 and 132: - 10 bit spreading code spreads sig
Page 133 and 134: Direct Sequence Spread Spectrum Usi
Page 135 and 136: 15.Additional Topics: Voice coders
Page 137 and 138: 'Toll Quality' voice coders, such a
Page 139 and 140: The well-known Shannon-Hartley law
Page 141 and 142: its for a known permutation of the
Page 143 and 144: 16. Question papers: B. Tech III Ye
Page 145 and 146: e received code word 110110. Commen
Page 147 and 148: 17. Question Bank 1. (a) State and
Page 149 and 150: 21. A Discrete Memory less Source (
Page 151 and 152: 19. Unit wise Bits CHOOSE THE CORRE
Page 153 and 154: (d) 5 Answers 1.C 2.D 3.B 4.A 5.C 6
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Page 157 and 158: (d) 6 5. The cascade of two binary
Page 159 and 160: CHOOSE THE CORRECT ANSWER 1. The mi
Page 161 and 162: 2.C 3.C 4.A 5.D 6.C 7.B 8.B 9.B 10.
Page 163 and 164: (b) H(X/Y)=1bit/message (c) H(X,Y)=
Page 165 and 166: (d) log m bits/symbol 6. Theencoder
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Page 169 and 170: 10.B Code No: 56026 Set No. 1 JAWAH
Page 171 and 172: code No: 56026 Set No. 2 JAWAHARLAL
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A) 5 B) 4 C) 2 D) 3 3. Which of the
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Code No: 56026 Set No. 2 JAWAHARLAL
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A) maximum when the source is conti
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Code No: 56026 :2: Set No. 4 II Fil
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Code No: 07A5EC09 Set No. 2 JAWAHAR
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Cont…..2 Code No: 07A5EC09 :2: Se
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8) For the data word 1110 in a (7,
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a) 0 bits b) 1 bit c) 2 bits d) inf
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a) increase with its certainty of o
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Code No: 07A5EC09 :2: Set No.4 10)
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Amplitude of 1v.This speech signal
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. Self Information c. Logarithmic m
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75. What are the advantages and dis
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22. Discussion Topics: Data transmi
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Applications and history Data (main
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o o Mesh network Wireless network A
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25. STUDENTS LIST B.TECH III YEAR I
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48 13R11A04L3 M SAI KUMAR 49 14R18A
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Group 8: 36 13R11A04K1 POLISETTY VE
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Unit 2 Pulse-Amplitude Modulation :
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Unit 3 Differential Pulse-Code Modu
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MISSING TOPICS UNIT 1 Hartley's law
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encoding the desired information an
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• f c denotes center frequency
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An interleaver installed between th
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Subject Contents 1.7. 1. Synopsis p
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