Transcript Lecture 12a - Rowan University

S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Electrical
Communications Systems
ECE.09.331
Spring 2010
Lecture 12a
April 13, 2010
Shreekanth Mandayam
ECE Department
Rowan University
http://engineering.rowan.edu/~shreek/spring10/ecomms/
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Plan
• Pulse Amplitude Modulation
• TDM Standards
• T1 (DS-1) Line
• North American TDMA Hierarchy
• Line Encoding
• Digital Bandpass Communications
•
•
•
•
•
•
Why digital modulation?
Digital Modulation: Introduction (ASK, FSK, PSK)
Binary Phase Shift Keying (BPSK)
Quadrature Phase Shift Keying (QPSK)
M-ary PSK and M-ary QAM
Observing Digital Bandpass Signals
• Constellation diagrams
• Eye Diagrams
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
ECOMMS: Topics
Electrical Communication Systems
Signals
Discrete
Systems
Continuous
Analog
Probability
Power & Energy Signals
AM
Switching Modulator
Envelop Detector
Information
Continuous Fourier Transform
DSB-SC
Product Modulator
Coherent Detector
Costas Loop
Entropy
Discrete Fourier Transform
SSB
Weaver's Method
Phasing Method
Frequency Method
Channel Capacity
Baseband and Bandpass Signals
Frequency & Phase Modulation
Narrowband/Wideband
VCO & Slope Detector
PLL
Digital
Digital Comm Transceiver
Baseband
CODEC
Bandpass
MODEM
Source Encoding
Huffman codes
ASK
PSK
FSK
Error-control Encoding
Hamming Codes
BPSK
Sampling
PAM
QPSK
Quantization
PCM
M-ary PSK
Line Encoding
QAM
Complex Envelope
Gaussian Noise & SNR
Time Division Mux
T1 (DS1) Standards
Random Variables
Noise Calculations
Packet Switching
Ethernet
ISO 7-Layer Protocol
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Sampling
Quantization
Source
Encoder
ADC
Data
Encryption
Encoder
Error
Control
Encoder
Channel/
Line
Encoder
Modulator
Analog i/p
CODEC
MODEM
Audio
Amp
Reconstruction/
DAC
Source
Decoder
Data
Encryption
Decoder
Error
Control
Decoder
DEMUX
Analog o/p
Equalization /
Decision
Circuits
Demodulator
Multiple access channel
Antialiasing
Filter
MUX
Digital Communications Transceiver
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Time Division Multiplexing
Message 1
Quantize
&
Encode
Message 2
Channel
Message N
Message 1
LPF
Message 2
LPF
Message N
LPF
Decode
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
T1-Line TDM Format
1 Frame = (24 Channels + F) = 125 ms
Channel 1
Channel 2
F 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
193 bits
Frame Sync Bit
Even Frames:
001110
Odd Frames:
101010
Every Sixth Frame
LSB (8th bit) is a Signaling bit
Bipolar R-Z Line Encoding
Channel 24
1 2 3 4 5 6 7 8
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
North American TDMA Hierarchy
64 kbs
1 VF
DS-0
1
24
1st
M
U
X
1
4
1
2nd
M
U
X
7
1
1
3rd
M
U
X
4th
6
M
U
X
2
5th
M
U
X
DS-1
DS-2
DS-3
DS-4
DS-5
1.44 Mbs
24 VF
6.312 Mbs
96 VF
44.736 Mbs
672 VF
274.176 Mbs
4032 VF
560.160 Mbs
8064 VF
•
•
•
Figure 3-40, p. 207 in Couch
Table 3-8, p. 208 in Couch
Table 3-9, p. 209 in Couch
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Sampling
Quantization
Source
Encoder
ADC
Data
Encryption
Encoder
Error
Control
Encoder
Channel/
Line
Encoder
Modulator
Analog i/p
CODEC
MODEM
Audio
Amp
Reconstruction/
DAC
Source
Decoder
Data
Encryption
Decoder
Error
Control
Decoder
DEMUX
Analog o/p
Equalization /
Decision
Circuits
Demodulator
Multiple access channel
Antialiasing
Filter
MUX
Digital Communications Transceiver
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Line Encoding
Couch, p. 157
Couch, p. 162
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
ECOMMS: Topics
Electrical Communication Systems
Signals
Discrete
Systems
Continuous
Analog
Probability
Power & Energy Signals
AM
Switching Modulator
Envelop Detector
Information
Continuous Fourier Transform
DSB-SC
Product Modulator
Coherent Detector
Costas Loop
Entropy
Discrete Fourier Transform
SSB
Weaver's Method
Phasing Method
Frequency Method
Channel Capacity
Baseband and Bandpass Signals
Frequency & Phase Modulation
Narrowband/Wideband
VCO & Slope Detector
PLL
Digital
Digital Comm Transceiver
Baseband
CODEC
Bandpass
MODEM
Source Encoding
Huffman codes
ASK
PSK
FSK
Error-control Encoding
Hamming Codes
BPSK
Sampling
PAM
QPSK
Quantization
PCM
M-ary PSK
Line Encoding
QAM
Complex Envelope
Gaussian Noise & SNR
Time Division Mux
T1 (DS1) Standards
Random Variables
Noise Calculations
Packet Switching
Ethernet
ISO 7-Layer Protocol
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Sampling
Quantization
Source
Encoder
ADC
Data
Encryption
Encoder
Error
Control
Encoder
Channel/
Line
Encoder
Modulator
Analog i/p
CODEC
MODEM
Audio
Amp
Reconstruction/
DAC
Source
Decoder
Data
Encryption
Decoder
Error
Control
Decoder
DEMUX
Analog o/p
Equalization /
Decision
Circuits
Demodulator
Multiple access channel
Antialiasing
Filter
MUX
Digital Communications Transceiver
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Digital Bandpass
Communications
• Why digital modulation?
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Industry Trends
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Applications
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Digital Modulation
Carrier signal:
Ac cos (2pfct + f)
Modulation:
Modulated signal:
m(t)
Ac (t) cos (2pfc(t) t + f(t))
 m(t); discrete
Vary
amplitude
Vary
frequency
Vary
phase
Variations are discrete!!!!!
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Recall: Dig Comm Principle
1 0 1 0………
1
AM
FM
PM
AM &
PM
0
Digital
code
Analog
message
0
1
Digital message
1
1
0
modulate
0
Sinusoidal carrier
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Signal Vector Representation
s(t) = Ac(t) cos (2pfct + f(t))
Q
fixed!!!
S
Phase
I
I-Q
Plane
0 degrees
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Signal Changes:
Representation in the IQ Plane
Magnitude
Change
Q
Q
Phase
S2 Change
S1
S2
I
Magnitude
& Phase
Q
Change
I-Q Diagrams
or
Constellations
S1
I
Frequency
Change
S1
S2
I
???
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Binary Phase Shift Keying
(BPSK)
s(t) = Ac cos(2pfct + f(t))
f(t)
IQ
Diagram
p radians
0 radians
1
t
Q
0
I
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Quadrature Phase Shift Keying
(QPSK)
IQ
Diagram
s(t) = Ac cos(2pfct + f(t))
Q
f(t)
3p/4
01
p/4
00
-p/4
-3p/4
10
11
11
10
p/4
t
01
I
00
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
M-ary Phase Shift Keying
(M-ary PSK)
Q
I
Octophase
I-Q
Constellation
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
M-ary Quadrature Amplitude Modulation
(M-ary-QAM)
Q
I
16 QAM
I-Q
Constellation
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Different ways of looking at
a digitally modulated signal
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Time & Frequency Domain View
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Frequency & Power View
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
I-Q Constellation Diagram
Matlab Demo:
qpsk.m
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Eye Diagram
Matlab:
>>eyediagram
Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf
S. Mandayam/ ECOMMS/ECE Dept./Rowan University
Summary