1. Lecture I Introduction to Digital Communications 1.Overview of comm. channels and digital links 2.Signal propagation through baseband PAM Links (ch. 1 – part 0 “Notes”) Following Lecture II next week: 2. …signal propagation through baseband PAM Links 3. Finite Energy Signal Space representations 4. Matched Filtering in AWGN for PAM antipodal links Read-ahead: Ch. 2 – part 0 “Notes”

2. “ The communication technology of a sufficiently advanced civilization is indistinguishable from magic”

3. Defining communications 1.What does it mean to communicate? Derived from the Latin communicare : to share to impart or to transmit Communication is the activity associated with transfering, distributing or exchanging information (usually spanning a distance) –One-way (one-to-one / one-to-many) –Two-way (one-to-one / many-to-many) Interactive Simultaneous

4. What do we communicate (information/messages)? Data / Text / Graphics / Voice / Music / Video How do we communicate? electro-magnetic signals carry the messages: 1.Analog signals (waveforms = continuous functions of time, assuming any value) 2.Digital signals (discrete-time and discrete-valued) binary bit-streams (…10011011010111001…) symbol-streams (…  …)

5. Digital Communication Link 1.Transmitter (TX) משדר 2.Medium (Channel תווך (ערוץ 3.Receiver (RX) מקלט DADAADAD

6. Medium (Channel תווך (ערוץ Wireless (Free space - vacuum / air); Radio, microwave, satellite, cellular, Wireless LAN Wireline: Telephone wires (twisted pairs) LAN (twisted pairs) RF cable (coaxial) Fiber optics May include active repeaters Satellite transponders Fiber optic repeaters

7. A digital Communications Link: bitstream-> TX->Analog Medium->RX > bitstream All media in Nature are analog – –A purely digital medium exists only in math. “Underneath every digital communications link there resides an analog medium” The TX: Digital->Analog The RX: Analog->Digital The objective of a communication link: Receiving a bitstream at the TX and faithfully reproducing it at the RX at maximum rate and with minimum power Bitstream: a finite or possibly infinite sequence of random bits out of the set {0,1}, representing the information to be carried (see Appendix to Lesson 1)

8. Two-way (full-duplex) links with modems

9. Telephony – Alexander Graham Bell receives a patent for the telephone (1876) the earliest form of “analog electrical communications”

10. Telegraphy (1843) the earliest form of “digital electrical communications” What’s wrong with this picture?

11. Data sources and pulse modulators

12. הדס 4

13. P-MOD example: QPSK transmitter mapping pairs of bits to one of four signals -

14. The transmitter’s most important block: P-MOD

15. Low-pass vs. Bandpass Media LowPass – Passes DC and low freq. –LowPass media: Telephone, LAN wires (RJ11/45) HighPass/Bandpass –Passes a passband of freq. –Wireless media don’t carry low freq. radiation efficiency negligible at low freq. –Certain wireline media are bandpass e.g. coaxial amplifiers are AC coupled

16. Model for LTI-AWGN medium Additive White Gaussian Noise

17. Model for zero-distortion idealized AWGN medium Frequency response B

18. End2end digital communication link Analog pulses Symbols (coded bits) uncoded bits (messages) Symbols (coded bits) uncoded bits (messages) Analog waveforms bits2symbols symbols2bits symbols2pulses waveforms2symbols

19. Complete digital communication link (more detail) A/D QUANTIZATION Data compression Redundant check-bits insertion

20. DATA LINK EXAMPLE

21. 16 QAM waveform code

22. Digital transmission formats for a binary stream

23. ASK, PSK, FSK Amp./Phase/Freq. Shift-Keying PSKFSK ASK

24. FSK transmitter

25. FSK Receiver

26. PAM – Pulse Amplitude Modulation P-MOD: PAM:

27. 4-level PAM transmission

28. Pulse Amplitude Modulation (PAM) k k Figure 1.12:

29. PAM modulator output waveform

30. Special case: Impulse Amp. Modulation (  PAM) – an ideal modelling device k k Figure 1.12:

31. “Single shot” @ t=0 – Isolated Pulse Amplitude Modulation P(t) t

32. General PAM Link Analysis Figure 1.17: (“multiple shots” analysis in TA classes…)

33. מועד א ' מערכת תקשורת ספרתית משדרת אחת מצורות הגל למשך זמן, כל T שניות ( הזמן t נמדד מחדש בתחילת כל קטע של T שניות ). קצב הסיביות ( מספר הביטים לשניה ) המשודר ע " י המערכת הוא : הפקולטה להנדסת חשמל8.7.2003 כיוונים בהנדסת חשמל (044115)