Transcript Communication Systems IK2506

Communication Systems
IK2506
Anders Västberg
[email protected]
08-790 44 55
IK2506 Advanced
Communication Systems
• TEN1: 6 HEC.
• INL1: 1,5 HEC.
– 3 Problem Assignments
• Required reading:
– Carlson, B., et. al., Communication Systems,
McGrawHill, 2002.
• Course Webpage:
– http://www.kth.se/student/programkurser/kurshemsidor/kurser-ict/cos/IK2506/HT091?l=en_UK
Teachers
• Anders Västberg (Examiner)
– [email protected]
– 08-790 44 55
• Svante Signell
– [email protected]
– 08-790 41 46
Supplementary rules for
examination
• Rule 1: All group members are responsible for
group assignments
• Rule 2: Document any help received and all
sources used
• Rule 3: Do not copy the solutions of others
• Rule 4: Be prepared to present your solution
• Rule 5: Use the attendance list correctly
For more information, see KTH rules at:
http://www.kth.se/dokument/student/student_rights.pdf
Mathematica and MATLAB
• Download the programs from:
– http://progdist.ug.kth.se/public/
• General introduction to Mathematica
– http://www.cos.ict.kth.se/~goeran/archives/Ma
thematica/Notebooks/General/
Carlson: Communication
Systems
Signals and
Spectra
Signal
Transmission
and Filtering
Analog
Modulation
Random
Signals and
Noise
Analog
Communication
Systems
Sampling and
Pulse
Modulation
Noise in Analog
Modulation
Systems
Digital
Modulation
Information
Theory
and Channel
Coding
[Stallings., 2005]
COS Wireless Courses
IK2511 Wireless
Network Project
IK2510 Wireless
Networks
Research Project
Radio Resource Management for
Wireless Networks
Data Transmission over Radio Channels,
Error Control Coding for Radio Channels
IK2508 Wireless
Transmission
IK2507 Wireless
Communication Systems
Radio Propagation,
Link Design and Diversity,
Spectrum Resource Management
IK2506 Advanced
Communication Systems
Signals, Systems and Spectra
Modulation, Stochastic Processes
Course Aim
• Give the student the ability to analyze the
design parameters of a communication
system. That means that the student should
be able to:
– Explain the system structure of analogue and
digital communication systems
– Use mathematical tools to analyse the
performance of communication systems
– Use probability theory and stochastic processes
in communication system applications.
Communication Systems
• Main functionality: Information Transfer
• Can not cover all types of communication
systems
• Can not cover the detailed implementation
– Look at system level
Types of Communication
Systems
• Analog Communication Systems
– Analog message: “Physical quantity that
varies with time”
• Digital Communication Systems
– Digital message: “Ordered sequence of
symbols selected from a finite set of discrete
elements”
Communication Systems
Source of
information
Message
signal
Transmitter
Transmitted signal
Channel
Estimate of
message
signal
Received signal
Receiver
Information
sink
[Ahlin et. al., 2006]
Basic Structure
• Transmitter
– Modulation
– Coding
• Transmission Channel
–
–
–
–
Loss or Attenuation
Distortion
Interference
Noise
• Receiver
– Amplification
– Demodulation and decoding
– Filtering
Alteration of the Signal
• Loss or Attenuation
– Can be compensated by amplification at the receiver
• Alteration of the Signal Shape
– Distortion
• Disappears when the signal is turned off
• Linear distortion may be corrected by the use of equalizers
(special filter).
– Interference
• Contamination by other signals from human sources
– Noise
• Contamination by signals from natural processes both
internal and external to the system
Types of Communication
• Simplex (SX)
– One way communication
• Full-duplex (FDX)
– Two way communication at the same time
• Half-duplex (HDX)
– Two way communication, but not at the same
time.
Fundamental Physical
Limitations
• Bandwidth
– If a signal changes
rapidly in time, its
frequency content or
spectrum extends
over a wide range, i.e.
the signal has a large
bandwidth
– Transmission
bandwidth
• Noise
– Thermal noise
C  2B log 2 M
C  B log 2 (1  S / N )
Analog Communication
System
Source of
information
Signal
Processing
Modulator
RF-Stage
Channel
Information
sink
Signal
Processing
Demodulator
RF-Stage
[Slimane]
Modulation
• Modulating signal
– Represent the message
• Carrier Wave
– Waveform the suits the application
• Modulation is a reversible operation
– Modulation – Demodulation
• Frequency translation
Modulation
• Modulation for Efficient Transmission
– Antennas should have a dimension of at least 1/10 of
the wavelength of the radio signal
• Modulation to Overcome Hardware Limitations
– Bandwidth should be at most 1/10 of the carrier
frequency
• Modulation to Reduce Noise and Interference
– Wideband noise reduction – Increase bandwidth to
reduce signal power
• Modulation for Frequency Assignment
• Modulation for Multiplexing
– Multiple Access
Digital Communication
System
Source of
Information
Source
Encoder
Channel
Encoder
Digital
Modulator
Modulator
RF-Stage
Channel
Information
Sink
Source
Decoder
Channel
Decoder
Digital
Demodulator
Demodulator
RF-Stage
[Slimane]
Coding
•
•
•
•
•
Modulation – Signal Processing Operation
Coding – Symbol Processing Operation
Encode – Decode
Channel Coding
Source Coding
decibels
•
The bel is a logarithmic unit of power ratios. One bel corresponds to an
increase of power by a factor of 10 relative to some reference power, Pref.
P[ bel ]
•




The bel is a large unit, so that decibel (dB) is almost always used:
P[ dB ]
•
 P
 log 10 
P
 ref
 P
 10 log 10 
P
 ref




The above equation may also be used to express a ratio of voltages (or
field strengths) provided that they appear across the same impedance (or
in a medium with the same wave impedance):
V[ dB]
 V
 20 log 10 
V
 ref




[Saunders, 1999]
decibels
Unit
Reference Power
Application
dBW
1W
Absolute power
dBm
1 mW
Absolute power
P [dbW] = P [dBm] - 30
dBmV
1 mV
Absolute voltage, typically at the input
terminals of a receiver
dB
any
Gain or loss of a network
dBmV/m
1 mV/m
Electric field strength
dBi
Power radiated by and isotropic
reference antenna
Gain of an antenna
dBd
Power radiated by a half-wave
dipole
Gain of an antenna
0 dBd = 2.15 dBi
[Saunders, 1999]
Signals
• Deterministic Signals
– Periodic Signals
– Non-Periodic
• Stochastic Signals
– Stationary
– Non Stationary