principles of communications 通訊原理

Principles of Communications通訊原理

Textbook : Communication Systems , 4th Edition

by Simon Haykin

John Wiley & Sons , Inc

歐亞書局代理Midterm 45% Final 45% Homework 10%

Contents

Background and Preview · Communication Process · Communication Networks

· Channels · Modulation Process · Analog and Digital Communications · A Digital Communication Problem · Historical Notes

Chapter 1 Random Process· Mathematical Definition of a Random Process· Stationary Processes· Mean , Correlation , and Covariance Functions · Ergodic Processes· Linear Time-Invariant Filter ( System ) · Power Spectral Density ( PSD )· Gaussian Process· Noise· Narrowband Noise· Representation of Narrowband Noise (I,Q, Envelope and phase )· Sinusoidal Wave Plus Narrowband Noise

Chapter 2 Continuous-Wave ( CW ) Modulation

· Amplitude Modulation (AM) · Linear Modulation Schemes· Frequency–Division Multiplexing ( FDM ) · Angle Modulation· Frequency Modulation ( FM ) · Nonlinear Effects in FM Systems· Superheterodyne Receiver · Noise in CW Systems ( Coherent Detection and Envelope Detection in A

M , Filtering in FM )

Chapter 3 Pulse Modulation · Sampling Process · Pulse-Amplitude Modulation (PAM)· Other Forms of Pulse Modulation (PPM,PDM) · Bandwidth-Noise Trade-off· Quantization · Pulse-Code Modulation (PCM)· Noise in PCM System· Time-Division Multiplexing (TDM)· Virtues , Limitations , and Modifications of PCM· Delta Modulation · Linear Prediction· Differential PCM (DPCM) , Adaptive DPCM (ADPCM)

Chapter 4 Baseband Pulse Transmission

· Matched Filter· Bit Error Rate ( BER ) Due to Noise· Intersymbol Interference ( ISI )· Nyquist’s Criterion for Distortionless Baseband Bi

nary Transmission· Correlative-Level Coding ( Partial-Response) · Digital Subscriber Loop· Optimum Linear Receiver· Adaptive Equalization

Chapter 5 Signal-Space Analysis

· Geometric Representation of Signals

· Conversion of the Continuous AWGN Channel into a Vector Channel

· Likelihood Functions

· Coherent Detection of Signal Noise:

Maximum Likelihood Decoding

· Correlation Receiver

· Probability of Error (BER)

Chapter 6 Passband Transmission

· Passband Transmission Model · Coherent Phase-Shift Keying (PSK)· Quadrature-Amplitude Modulation (QAM)· Coherent Frequency-Shift Keying (FSK)· Detection of Signals with Unknown Phase· Noncoherent Orthogonal Modulation· Noncoherent Binary FSK· Comparison of Digital Modulation Schemes Using

a Single Carrier

Background And Preview

0.1 The Communication Process (Statistical)- Communication anywhere , anytime , involving

transmission of information from one point to other places, (Broadcasting , Point-to-point) generation and description of signals, encoding, transmission, decoding and recovering.

0.2 Primary Communication Resources

- transmitted power - channel bandwidth

Due to noise , the ratio of the average signal power to the average noise power (SNR) is an important system parameter (in terms dB) , but not the only one

0.3 Sources of Information

- Speech

production , propagation , perception

- Music

melodic structure 旋律 harmonic structure 音調和諧 - Picture

0.4 Communication Networks

- Open Systems Interconnection (OSI) Reference Model

Internet A specific worldwide internet. A machine is on the Internet if it runs the TCP/IP protocol stack , has an

IP address, and has the ability to send and receive IP packets to all the other machines on the Internet.

The network technology is decoupled fromthe applications.

· The applications are carried out independently of the technology · The network technology is capable of evolving without affecting the applications

Broadband Networks

Driving forces : demand for new services(video , multimedia ) and enabling technologies (optical fibers, packet digital switches )

ATM, SONET, SDH, PDH (Plesiochronous Digital Hierarchy )

0.5 Communication Channels

- Guided Propagation

a. Telephone Channels

(twisted pair of wires)

b.Coaxial Channel ( 50Ω ,75Ω )c.Optical Fiber (single mode, multimode) 125 μm

cladding 8 μm core ·Enormous potential bandwidth (70 x 1012 Hz ) ·Low transmission losses (0.158 db/km at 1.55μm )·Immunity to electromagnetic interference·Small size and weight· Ruggedness and flexibility

d. Wireless broadcast channels (AM,FM,TV) superheterodyne receiverse. Mobile radio channels multipath fading , dispersivef. Satellite channels (geosynchronous , low orbit) Broad-area coverage, reliable transmission lines,wide transmission bandwidth

Classification of channelsa. Linear, nonlinear (e.g. satellite)b. Time invariant, time variantc. Bandwidth limited (e.g. telephone channel) Power limited (e.g. satellite)

0.6 Modulation and Demodulation Processes a. Continuous-Wave (CW) modulation - amplitude modulation ( AM ) - frequency modulation ( FM ) - phase modulation ( PM ) b. Pulse modulation - pulse-amplitude modulation ( PAM ) - pulse-duration modulation ( PDM ) - pulse-positive modulation ( PPM )

c. Pulse-code modulation ( PCM,digital ) - Sampling , quantization , coding - Properties of PCM · Robustness in noisy environments · Flexible operation · Integration of diverse sources into a common format (0.1) · Security of information

0.7 Multiplexing a. Frequency-division multiplexing ( FDM ) b. Time-division multiplexing ( TDM ) c. Code-division multiplexing ( CDM )

0.8 Analog and Digital Types of Communications a. Guidelines of designing the transmitter and the receiver - Encode/modulate the signal,transmit it over the channel and produce an ’’estimate” of the original signal at the receiver output that satisfies the requirements - Do all of this at an affordable cost b. The design of an analog communication system is conceptually simple but difficult to implement

c. The digital communication system

- Source encoder-decoder

- Channel encoder-decoder

- Modulator-demodulator

0.9 Shannon’s Information Capacity Theorem

C = B · log2(1+SNR) b/s (1)

C : Channel capacity

B : Channel bandwidth

SNR : Signal-to-noise ratio

Efficiency of a digital communication system

= R/C R: actual signaling rate

Equation 1 provides a basis for the trade-off between B and SNR and an idealized framework for comparing modulation schemes

0.10 A Digital Communication Problem (band pass)

The random signal m(t) consists of symbols 1 and 0 with duration T.For PSK,

s(t)= -Ac cos(2fct+m(t) )

where 0 t T , the carrier frequency fc= , k=integer, Ac is the amplitude.

Assume the channel is distortionless but noising , the received

signal x(t) is

x(t)=s(t)+w(t) (3)where w(t) is the additive channel noise (e.g., AWGN).

The output of the correlator is

Decision rule :

If yT 0 output symbol=1

yT 0 output symbol=0

T

k

TwA

wA

c

c

2

2 T (5)=

for m (t) =1

for m (t) = 0

TwdttftsyT

cT 0 )2cos()( (4)

(2)

Important Issues a. time-bandwidth product of a pulse signal is constant, e.g., the bandwidth of a rectangular pulse of duration T is inversely proportional to T

b. frequency shifting (Fourier Transform) c. signal rate on d. justification of the receiver structure

e. relation between wT and w(t) f. BER(modulation,channel,noise,demodulation) g. choice of modulation schemes, coding, synchronization

TB

1

Tsb 1

0.11 Historical Notes

1837 Morse, Telegraph , Morse Code1875 Baudot, Fixed length code (five elements)1964 Maxwell, EM theory1987 Hertz, Radio wave 1894 Lodge, Wireless communication1901 Marconi, Long distance radio communication1875 Bell, Telephone1897 Stowger, Step-by-step switch 1904 Fleming, Vacuum tube diode1906 Lee de Forest, Vacuum tube triode

1918 Armstrong ,Superheterdyne radio receiver1936 Armstrong, Frequency modulation1928 Nyquist, Nyquist’s criteria1937 Reeves, Pulse-code modulation ( PCM )1947 Kotel’nikov, Representation of signals1948 Shannon, Information Theory1949 Golay, Error-correcting codes1950 Hamming, Hamming codes1948 Brattain, Bardeen, and Schockley,Transistor1958 Noyce, IC1962 Bell Labs, TI carrier system1946 Univ. of Penn, Computer1976 ARPA, Computer networks 1955 Pierce, Satellite communication1966 K.C. Kao and Hockham, Fibers