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ارتباطات داده (883-40) انتقال دیجیتال باندمیانی

ارتباطات داده (883-40) انتقال دیجیتال باندمیانی. دانشکده مهندسی کامپیوتر. نیمسال دوّم 93-92 افشین همّت یار. Passband Digital Transmission. Introduction Passband Transmission Model Coherent Phase-Shift Keying Hybrid Amplitude/Phase Modulation Schemes Coherent frequency-Shift Keying

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ارتباطات داده (883-40) انتقال دیجیتال باندمیانی

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  1. ارتباطات داده (883-40)انتقال دیجیتال باندمیانی دانشکده مهندسی کامپیوتر نیمسال دوّم 93-92 افشین همّتیار

  2. Passband Digital Transmission • Introduction • Passband Transmission Model • Coherent Phase-Shift Keying • Hybrid Amplitude/Phase Modulation Schemes • Coherent frequency-Shift Keying • Detection of Signals with Unknown Phase • Noncoherent Orthogonal Modulation • Noncoherent Binary Frequency-Shift Keying • Differential Phase-Shift Keying • Comparison of Digital Modulation Schemes Using a Single Carrier • Voiceband Modems • Multichannel Modulation • Discrete Multitone • Synchronization

  3. Introduction (1) • Amplitude Shift Keying • Phase Shift Keying • Frequency Shift Keying • (with continuous phase)

  4. Introduction (2) • Digital Modulation Techniques: • Coherent • Non-coherent • M-ary Signaling Schemes: • M-ary ASK • M-ary PSK • M-ary FSK • M-ary Amplitude-Phase Shift Keying (APK) • (Special case: Quadrature Amplitude Modulation (QAM)

  5. Introduction (3) Power Spectra: Passband Signal Baseband Signal (Complex) Power Spectral Density Bandwidth Efficiency:

  6. Passband Transmission Model • Two assumptions for Channel: • Channel is linear with wide enough bandwidth no distortion • Channel noise is zero-mean white Gaussian

  7. Coherent Phase-Shift Keying (1) (BPSK: Constellation)

  8. Coherent Phase-Shift Keying (2) • (BPSK: Signal-Space Diagram)

  9. Coherent Phase-Shift Keying (3) • (BPSK: Error Probability)

  10. Coherent Phase-Shift Keying (4) • (BPSK: Generation and Coherent Detection) Binary PSK Transmitter Coherent Binary PSK Receiver

  11. Coherent Phase-Shift Keying (5) (BPSK: Power Spectra) Pulse Shaping Function: Baseband Power Spectrum

  12. Coherent Phase-Shift Keying (6) (QPSK: Constellation)

  13. Coherent Phase-Shift Keying (7) • (QPSK: Signal-Space Diagram)

  14. Coherent Phase-Shift Keying (8) • (QPSK: Example 6.1)

  15. Coherent Phase-Shift Keying (9) • (QPSK: Error Probability) for each channel of QPSK

  16. Coherent Phase-Shift Keying (10) • (QPSK: Error Probability) another way nearest and

  17. Coherent Phase-Shift Keying (11) • (QPSK: Generation and Coherent Detection) QPSK Transmitter Coherent QPSK Receiver

  18. Coherent Phase-Shift Keying (12) (QPSK: Power Spectra) Pulse Shaping Function: Baseband Power Spectrum

  19. Coherent Phase-Shift Keying (13) (OffsetQPSK) only ±90° phase transitions but twice as frequently ±180° & ±90° phase transitions QPSK Offset QPSK Possible paths for switching between message points Same probability of error Basis Functions

  20. Coherent Phase-Shift Keying (14) (π/4 Shifted QPSK) QPSK π/4 Shifted QPSK Possible paths for switching between message points

  21. Coherent Phase-Shift Keying (15) (π/4 Shifted DQPSK) Noncoherent Detector

  22. Coherent Phase-Shift Keying (16) (π/4 Shifted DQPSK: Example 6.2)

  23. Coherent Phase-Shift Keying (17) • (M-ary PSK: Signal-Space Diagram)

  24. Coherent Phase-Shift Keying (18) • (M-ary PSK: Error Probability) • (M-ary PSK: Power Spectra) Baseband Power Spectrum

  25. Coherent Phase-Shift Keying (19) • (M-ary PSK: Bandwidth Efficiency)

  26. Hybrid Amplitude/Phase Modulation Schemes (1) M-ary QAM is a two-dimensional generalization of M-ary PAM. M-ary QAM Square Constellation: (M=L2) Cartesian Product of L-ary PAM constellation PAM

  27. Hybrid Amplitude/Phase Modulation Schemes (2) (M-ary QAM: Probability of Error) Probability of correct detection: (M=L2) Probability of symbol error for L-ary PAM Probability of symbol error for M-ary QAM:

  28. Hybrid Amplitude/Phase Modulation Schemes (3) (M-ary QAM: Cross Constellation) (for odd number of bits per symbol) 2n-1 + 4x(2n-3) = 2n

  29. Hybrid Amplitude/Phase Modulation Schemes (4) (CAP: Carrierless Amplitude/Phase Modulation)

  30. Hybrid Amplitude/Phase Modulation Schemes (5) (CAP: Presentation) • The transmitted signal s(t) appears to be carrierless. • The transmitted signal s(t) represents a symbol-time-invariant • realization of hybrid amplitude and phase modulation. • Ignoring rotation 

  31. Hybrid Amplitude/Phase Modulation Schemes (6) (CAP: Properties)

  32. Hybrid Amplitude/Phase Modulation Schemes (7) (CAP: Example)

  33. Hybrid Amplitude/Phase Modulation Schemes (8) (CAP: Basic Structure)

  34. Hybrid Amplitude/Phase Modulation Schemes (9) (CAP: Basic Structure)

  35. Hybrid Amplitude/Phase Modulation Schemes (10) (CAP: Digital Implementation of CAP Receiver)

  36. Coherent frequency-Shift Keying (1) (BFSK: Constellation) (Continuous Phase FSK)

  37. Coherent frequency-Shift Keying (2) (BFSK: Signal-Space Presentation)

  38. Coherent frequency-Shift Keying (3) (BFSK: Probability of Error) Same for p01

  39. Coherent frequency-Shift Keying (4) • (BFSK: Generation and Coherent Detection) Transmitter Coherent Receiver

  40. Coherent frequency-Shift Keying (5) • (BFSK: Power Spectra) Baseband Power Spectrum

  41. Coherent frequency-Shift Keying (6) • (MSK: Minimum Shift Keying) CPFSK Angle Modulated Signal Center Frequency Deviation Ratio

  42. Coherent frequency-Shift Keying (7) • (MSK: Phase Trellis) h=1 h=0.5 h=1 πh is same as –πh No memory (minimum value for orthogonal basis) h=0.5  ±π/2 at odd multiples of Tb and 0 , π at even multiples of Tb Phase Tree Phase Trellis: Boldfaced path represents the sequence 1101000.

  43. Coherent frequency-Shift Keying (8) • (MSK: Signal-Space Diagram) Half Cycle Cosine Pulse: Half Cycle Sine Pulse:

  44. Coherent frequency-Shift Keying (9) • (MSK: Signal-Space Diagram)

  45. Coherent frequency-Shift Keying (10) • (MSK: Signal-Space Diagram)

  46. Coherent frequency-Shift Keying (11) • (MSK: Signal-Space Diagram)

  47. Coherent frequency-Shift Keying (12) • (MSK: Example)

  48. Coherent frequency-Shift Keying (13) • (MSK: Probability of Error) Same as BPSK and QPSK(BER) This good performance is the result of the detection of the MSK signal being performed in the receiver on the observation over 2Tb interval.

  49. Coherent frequency-Shift Keying (14) • (MSK: Generation and Coherent Detection) Transmitter Coherent Receiver

  50. Coherent frequency-Shift Keying (15) • (MSK: Power Spectra) 3. In-phase and quadrature components are statistically independent. Hence the baseband power spectral density is given by:

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