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information is around 56 k bits/second and transmit digital information is around 33 k bits/second. A Local Area Network (LAN) can theoretically receive/transmit information at a rate of 100 M bits/s. Gigabit networks would be able to receive/transmit information at least 10 times that rate. Modulation: is changing one or more of the characteristics of a signal (known as the carrier signal) based on the value of another signal (known as the information or modulating signal) to produce a modulated signal. Analog and Digital Communications Since the introduction of digital communication few decades ago, it has been gaining a steady increase in use. Today, you can find a digital form of almost all types of analog communication systems. For example, TV channels are now broa<strong>dc</strong>asted in digital form (most if not all Ku–band satellite TV transmission is digital). Also, radio now is being broa<strong>dc</strong>asted in digital form (see sirus.com and xm.com). Home phone systems are starting to go digital (a digital phone system is available at KFUPM). Almost all cellular phones are now digital, and so on. So, what makes digital communication more attractive compared to analog communication? Advantages of Digital Communication over Analog Communication • Immunity to Noise (possibility of regenerating the original digital signal if signal power to noise power ratio (SNR) is relatively high by using of devices called repeaters along the path of transmission). • Efficient use of communication bandwidth (through use of techniques like compression). • Digital communication provides higher security (data encryption). • The ability to detect errors and correct them if necessary. • Design and manufacturing of electronics for digital communication systems is much easier and much cheaper than the design and manufacturing of electronics for analog communication systems. Modulation Famous Types • Amplitude Modulation (AM): varying the amplitude of the carrier based on the information signal as done for radio channels that are transmitted in the AM radio band. • Phase Modulation (PM): varying the phase of the carrier based on the information signal. • Frequency Modulation (FM): varying the frequency of the carrier based on the information signal as done for channels transmitted in the FM radio band. Purpose of Modulation • For a signal (like the electric signals coming out of a microphone) to be transmitted by an antenna, signal wavelength has to be comparable to the length of the antenna (signal wavelength is equal to 0.1 of the antenna length or more). If
the wavelength is extremely long, modulation must be used to reduce the wavelength of the signal to make the length of the required antenna practical. • To receive transmitted signals from multiple sources without interference between them, they must be transmitted at different frequencies (frequency multiplexing) by modulating carriers that have different frequencies with the different information signals. Exercise 1–1: Specify if the following communication systems are (A)nalog or (D)igital: a) TV in the 1970s: b) TV in the 2030s: c) Fax machines d) Local area networks (LANs): e) First–generation cellular phones f) Second–generation cellular phones g) Third–generation cellular phones
Page 1 and 2: DC COURSE FILE
Page 3 and 4: GEETHANJALI COLLEGE OF ENGINEERING
Page 5 and 6: Convolution Codes: Encoding, decodi
Page 7 and 8: III. To inculcate positive attitude
Page 9 and 10: 7. Importance of the course and how
Page 11 and 12: DC 12: Compute the power and bandwi
Page 13 and 14: 10. Course mapping with PEO’s and
Page 15 and 16: 13.Micro plan : Sl. no Unit No. Tot
Page 17 and 18: 14.Detailed Notes UNIT 1 : Elements
Page 19: A communication system may transmit
Page 25 and 26: asic elements of digital communicat
Page 27 and 28: 4. Channel introduced many types of
Page 29 and 30: 5. Bandwidth is another scarce reso
Page 35 and 36: Pulse Code Modulation ‣ PCM gener
Page 37: 77777333333333333333333333333333333
Page 40 and 41: • The most common technique for s
Page 42 and 43: Pulse Code Modulation (PCM) : • P
Page 44 and 45: Figure 3.11 Illustration of the qua
Page 46 and 47: Quantization (nonuniform quantizer)
Page 48 and 49: Time-Division Multiplexing(TDM):
Page 50 and 51: Let m n where T The error signal is
Page 52 and 53: 3. Simplify receiver design Because
Page 54 and 55: Figure 3.27 Block diagram illustrat
Page 56 and 57: Adaptive Differential Pulse-Code Mo
Page 59 and 60: ASK, OOK, MASK: • The amplitude (
Page 61 and 62: Frequency Shift Keying: • One fre
Page 63 and 64: s t Acos 2f ct 3 Acos 2f
Page 65 and 66: QAM and QPR: • QAM is a combinati
Page 67 and 68: Generation and Detection of Coheren
Page 69 and 70: Figure 6.29 Signal-space diagram fo
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UNIT 3 Base Band Transmission And O
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• The tails of hI(t) decay as 1/|
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• precoding d b d k k k2 symbol 1
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h( t) N 1 n w n sin c t T b
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• Equalization : to compensate fo
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e n y n 2E en 2E en 2Eenxnk
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- Flexibility - Same H/W may be tim
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Interpretation of Eye Diagram:
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The set of source symbols is called
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We will usually neglect to mention
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Note that if Condition1 is satisfie
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where dmin is the minimum Hamming d
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Linear Block Codes - example 1: •
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• S null can be represented by it
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G 1 0 I | P 0 0 0 1 0 0 0 0
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• Compared with the systematic co
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Convolutional Codes ◊ The encoder
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Convolution Codes ‣ Encoding, ‣
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x m m ''' j j 2 j Here each messa
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Representing convolutional codes: C
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- encoder state diagram for (n,k,L)
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• For this reason the non-survive
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sequence is 1 1 0 0 0 0 0 (why?). N
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Error Correction: • If there is n
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correct:1+1+2+2+2=8;8 ( 0.11) 0.88
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Motivation: Performance of Turbo Co
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Performance as a Function of Number
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General Model of Spread Spectrum Sy
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Slow and Fast FHSS: • Frequency s
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- 10 bit spreading code spreads sig
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Direct Sequence Spread Spectrum Usi
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15.Additional Topics: Voice coders
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'Toll Quality' voice coders, such a
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The well-known Shannon-Hartley law
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its for a known permutation of the
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16. Question papers: B. Tech III Ye
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e received code word 110110. Commen
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17. Question Bank 1. (a) State and
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21. A Discrete Memory less Source (
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19. Unit wise Bits CHOOSE THE CORRE
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(d) 5 Answers 1.C 2.D 3.B 4.A 5.C 6
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(b) its capacity gets doubled (c) i
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(d) 6 5. The cascade of two binary
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CHOOSE THE CORRECT ANSWER 1. The mi
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2.C 3.C 4.A 5.D 6.C 7.B 8.B 9.B 10.
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(b) H(X/Y)=1bit/message (c) H(X,Y)=
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(d) log m bits/symbol 6. Theencoder
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3. .Under error free reception, the
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10.B Code No: 56026 Set No. 1 JAWAH
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code No: 56026 Set No. 2 JAWAHARLAL
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B) (Power required)/( Minimum Band
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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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