ECE 4371, Fall, 2014 Introduction to Telecommunication Engineering/Telecommunication LaboratoryOutlineGray CodeBasic steps for spectrum analysisDigital Communication SystemNRZRZ schemePolar biphase: Manchester and differential Manchester schemesBipolar schemes: AMI and pseudoternaryMultilevel: 2B1Q schemePulse ShapingSmall questions in exam 2ScramblingSlide 14Scrambling ExampleVideo StandardDiscrete Cosine Transform (DCT)DCT and Huffman CodingBasis vectorsUsing DCT in JPEGComparison of DF and DCTQuantization and Coding30:1 compression and 12:1 CompressionMotion CompensationMotion PredictionMotion Compensation Approach(cont.)Motion estimation for different framesA typical group of pictures in display orderCoding of MacroblockA Simplified MPEG encoderMPEG StandardsSlide 32JPEGDVHDTV 4KTVECE 4371, Fall, 2014Introduction to Telecommunication Engineering/Telecommunication Laboratory Zhu HanDepartment of Electrical and Computer EngineeringClass 11Oct. 1st, 2014OutlineOutlineGray Code Line Coding Spectrum Scrambler Multimedia TransmissionGray CodeGray CodeThe reflected binary code, also known as Gray code, Two successive values differ in only one digit. http://en.wikipedia.org/wiki/Gray_codeIf you check the chip, they have the bus number ordered in Gray code.Basic steps for spectrum analysisBasic steps for spectrum analysisFigure–Basic pulse function and its spectrum P(w)For example, rect. Function (in time) is sinc function (in freq.)–Input x is the pulse function with different amplitude Carry different information with sign and amplitudeAuto correlation is the spectrum of Sx(w)–Overall spectrum01lim1 1( ) 2b bbn k k nTkjnwT jnwTx n nn nb bTR a aTS w R e R R eT T+��� �- -=- � ==� �= = +� �� ��� �2( ) ( ) ( )y yS w P w S w=xDigital Communication SystemDigital Communication SystemSpectrum of line coding:–Basic pulse function and its spectrum P(w)For example, rect. function is sinc–Input x is the pulse function with different amplitudeCarry different information with sign and amplitudeAuto correlation is the spectrum of Sx(w)–Overall spectrum01lim1 1( ) 2b bbn k k nTkjnwT jnwTx n nn nb bTR a aTS w R e R R eT T+��� �- -=- � ==� �= = +� �� ��� �)()()(2wSwPwSxyNRZNRZR0=1, Rn=0, n>0Pulse width Tb/2P(w)=Tb sinc(wTb/2)Bandwidth Rb for pulse width TbRZ schemeDC NullingSplit phase   44sin2TTTRtrPolar biphase: Manchester and differential Manchester schemesIn Manchester and differential Manchester encoding, the transition at the middle of the bit is used for synchronization.The minimum bandwidth of Manchester and differential Manchester is 2 times that of NRZ. 802.3 token bus and 802.4 EthernetBipolar schemes: AMI and pseudoternaryR0=1/2, R1=-1/4, Rn=0,n>1, Reason: the phase changes slower[ ]22 2( )( ) 1 cos sin sin2 4 4 2b b by bbP wT wT wTS w wT cT� � � �= - =� � � �� � � �EE 541/451 Fall 2006Multilevel: 2B1Q schemeNRZ with amplitude representing morebitsPulse ShapingPulse ShapingSy(w)=|P(w)|^2Sx(w)–Sx(w) is improved by the different line codes.–p(t) is assumed to be squareHow about improving p(t) and P(w)–Reduce the bandwidth –Reduce interferences to other bands–Remove Inter-symbol-interference (ISI)–In wireless communication, pulse shaping to further save BW–Talk about the pulse shaping laterSmall questions in exam 2Small questions in exam 2Draw the spectrums of three different line codes and describe why the spectrums have such shapes.ScramblingScramblingMake the data more random by removing long strings of 1’s or 0’s. Improve timingThe simplest form of scrambling is to add a long pseudo-noise (PN) sequence to the data sequence and subtract it at the receiver (via modulo 2 addition); a PN sequence is produced by a Linear Shift Feedback Register (LSFR).In receiver, descrambling using the same PN.Secure: what is the PN and what is the initialdatascrambleddataPN sequence length2m – 1 = 26 – 1 = 63ScramblingScramblingExercise: 100000000000Scrambling ExampleScrambling ExampleScramblerDescramblerVideo StandardVideo StandardTwo camps–H261, H263, H264; –MPEG1 (VCD), MPEG2 (DVD), MPEG4Spacial Redundancy: JPEG–Intraframe compression–DCT compression + Huffman codingTemporal Redundancy –Interframe compression–Motion estimationDiscrete Cosine Transform (DCT)Discrete Cosine Transform (DCT)120 108 90 75 69 73 82 89127 115 97 81 75 79 88 95134 122 105 89 83 87 96 103137 125 107 92 86 90 99 106131 119 101 86 80 83 93 100117 105 87 72 65 69 78 85100 88 70 55 49 53 62 6989 77 59 44 38 42 51 580 – black255 – whiteDCT and Huffman CodingDCT and Huffman Coding0 – black255 – white700 90 100 0 0 0 0 090 0 0 0 0 0 0 0-89 0 0 0 0 0 0 00 0 0 0 0 0 0 00 0 0 0 0 0 0 00 0 0 0 0 0 0 00 0 0 0 0 0 0 00 0 0 0 0 0 0 0Basis vectorsBasis vectorsUsing DCT in JPEG Using DCT in JPEG  DCT on 8x8 blocksComparison of DF and DCTComparison of DF and DCTQuantization and CodingQuantization and CodingZonal Coding: Coefficients outside the zone mask are zeroed. •The coefficients outside the zone may contain significant energy•Local variations are not reconstructed properly30:1 compression and 12:1 Compression30:1 compression and 12:1 CompressionMotion CompensationMotion CompensationI-Frame–Independently reconstructedP-Frame–Forward predicted from the last I-Frame or P-FrameB-Frame–forward predicted and backward predicted from the last/next I-frame or P-frameTransmitted as - I P B B B P B B BMotion PredictionMotion PredictionMotion Compensation Approach(cont.)Motion Compensation Approach(cont.)Motion Vectors–static background is a very special case, we should consider the displacement of the block.–Motion vector is used to inform decoder exactly where in the previous image to get the data.–Motion vector would be zero for a static background.Motion estimation for different framesMotion estimation for different framesX ZYAvailable from earlier frame (X)Available from later frame (Z)A typical group of pictures in display orderA typical group of pictures in display orderA typical group of pictures in coding order1 5 2 3 4 9 6 7 8 13 10 11 12I P B B B P B B B P B B BI B B B P B B B P B B B PCoding of MacroblockCoding of