ELEN602 Lecture 3 Review of last lecture layering IP architecture Data Transmission Abstract View of Data Transmission Transmitter Receiver Communication channel Communication Channel Properties Bandwidth Transmission and Propagation Delay Jitter Loss Error rates Buffering Analog vs Digital Transmission a Analog transmission all details must be reproduced accurately Sent Received e g AM FM TV transmission b Digital transmission only discrete levels need to be reproduced Sent Received e g digital telephone CD Audio A Typical Communication Channel Transmission segment Source Repeater Repeater Destination An Analog Repeater Attenuated distorted signal noise Amp Repeater Equalizer Recovered signal residual noise A Digital Repeater Decision Circuit Signal Regenerator Amplifier Equalizer Timing Recovery 0110101 d meters communication channel 0110101 Characteristics of an Idealized Channel a Lowpass and idealized lowpass channel A f A f 0 f W 1 f 0 W b Maximum pulse transmission rate is 2W pulses second Nyquist rate Channel t t Impact of Noise on Communication signal signal noise noise High SNR t t t noise signal signal noise Low SNR t t SNR Average Signal Power Average Noise Power SNR dB 10 log10 SNR t Channel Characterization Frequency Domain Aincos 2 ft Aoutcos 2 ft f Channel t t A f Aout Ain Signal Amplitude Attentuation 1 A f 1 1 4 2f2 f Signal Phase Modulation f tan 1 2 f 0 1 2 f 45o 90o A Pulse 10 0 00 001 t 1 ms Output of Low pass Communication Channel 1 0 8 7 5 0 7 5 0 6 2 5 0 5 0 3 7 5 0 2 5 0 1 2 5 0 1 0 8 7 5 0 7 5 0 6 2 5 0 5 0 3 7 5 0 2 5 0 1 2 5 1 0 8 7 5 0 7 5 0 6 2 5 0 3 7 5 0 2 5 0 5 c 4 H a rm o n ic s 0 1 2 5 1 5 1 0 5 0 0 5 1 1 5 b 2 H a rm o n ic s 0 1 5 1 0 5 0 0 5 1 1 5 a 1 H a rm o n ic 0 1 5 1 0 5 0 0 5 1 1 5 Channel Characterization Time Domain h t Channel 0 t t td Signaling a Pulse with Zero Inter symbol Interference s t sin 2 Wt 2 Wt 1 2 1 0 8 0 6 0 4 0 2 t 0 7T 6T 5T 4T 3 T 2 T 1 0 2 T 0 0 4 1T 2T 3T 4T 5 T 6 T 7 T Digital Baseband Signal and Baseband Tx System 1 0 1 1 0 1 0 T 2T 3T 4T 5T A A Transmitter Filter Comm Channel Receiver Filter t r t Receiver Received signal a 3 separate pulses for sequence 110 1 0 2 T 1T 0 1T 2T 3T 4T t 1 b Combined signal for sequence 110 2 1 t 0 2T 1T 0 1 2 1T 2T 3T 4T typical noise 4 signal levels 8 signal levels Signal levels Error Probability 1 00E 00 1 00E 01 1 00E 02 1 00E 03 1 00E 04 1 00E 05 1 00E 06 1 00E 07 1 00E 08 1 00E 09 1 00E 10 1 00E 11 1 00E 12 0 2 4 2 A M 1 Channel Capacity W log 1 SNR 6 8 2 1 Unipolar NRZ Polar NRZ NRZ Inverted Differential Encoding Bipolar Encoding Manchester Encoding Differential Manchester Encoding 0 1 0 1 1 1 0 0 Coding Methods Properties Unipolar NRZ power A 2 2 Polar NRZ power A 2 4 Bipolar encoding reduces the low frequency spectrum Timing Recovery is also easier used in telephones NRZ Inverted A transition means 1 no transition is 0 Errors occur in pairs Ethernet uses Manchester encoding A transition from to is 1 to is 0 in the middle Twice the pulse rate of binary coding Differential Manchester encoding used in Token rings Every pulse has a transition in the middle A transition at the beginning is 0 no transition is 1 1 2 NRZ Bipolar 0 8 0 6 0 4 Manchester 0 2 fT 2 1 8 1 6 1 4 1 2 1 0 8 0 6 0 4 0 2 0 2 0 0 pow er density 1 0 f1 fc f2 f Figure 3 27 Amplitude Frequency and Phase Modulation Informatio n a 1 0 1 1 0 1 1 Amplitude Shift Keying 1 0 T 2T 3T 4T 5T 6T 0 T 2T 3T 4T 5T 6T 0 T 2T 3T 4T 5T 6T t 1 b Frequency Shift Keying 1 c Phase Shift Keying t 1 1 t 1 a Information 0 1 1 0 1 A b Baseband Signal Xi t T 0 2T 3T 4T 5T t 6T A A c Modulated Signal Yi t 0 2T T 3T 4T 5T 6T t 6T t A 2A d 2Yi t cos 2 fct 2A 0 T 2T 3T 4T 5T Modulator and Demodulator a Modulate cos 2 fct by multiplying it by Ak for k 1 T t kT Ak x Yi t Ak cos 2 fct cos 2 fct b Demodulate recover Ak by multiplying by 2cos 2 fct and lowpass filtering Yi t Akcos 2 fct x 2cos 2 fct Lowpass Filter with cutoff W Hz Xi t 2Ak cos2 2 fct Ak 1 cos 2 fct QAM Modulator Modulate cos 2 fct and sin 2 fct by multiplying them by Ak and Bk respectively for k 1 T t kT Ak x Yi t Ak cos 2 fc t cos 2 fc t Bk x sin 2 fc t Yq t Bk sin 2 fc t Y t QAM Demodulator Y t Lowpass Filter with cutoff W 2 Hz x 2cos 2 fc t x 2sin 2 fc t Ak 2cos2 2 fct 2Bk cos 2 fct sin 2 fct Ak 1 cos 4 fct Bk 0 sin 4 fct Lowpass Filter with cutoff W 2 Hz Bk 2Bk sin2 2 fct 2Ak cos 2 fct sin 2 fct Bk 1 cos 4 fct Ak 0 sin 4 fct Signal Constellations 2 D signal Bk Bk 2 D signal Ak Ak 4 levels pulse 2 bits pulse 2W bits per second 16 levels pulse 4 bits pulse 4W bits per second Other Signal Constellations Bk Bk Ak Ak 4 levels pulse 2 bits pulse 2W bits per second 16 levels pulse 4 bits pulse 4W bits per second Electromagnetic Spectrum 102 10 10 2 1014 1016 1018 10 4 10 6 Wavelength meters 10 8 10 10 1020 1022 1024 gamma rays 1012 ultraviolet light broadcast radio 104 1010 visible light 108 infrared light 106 106 microwave radio 104 power telephone 102 x rays Frequency Hz 10 12 10 14 Twisted Pair Attentuation vs Frequency 26 gauge 30 24 gauge 27 Attenuation dB mi 24 22 gauge 21 18 19 gauge 15 12 9 6 3 1 10 100 1000 f kHz Figure 3 37 Coaxial Cable Center conductor Dielectric material …