Wireless Communications & Spread Spectrum Design

Professional Development Short Course On:

Wireless Communications & Spectrum Design

Instructor:

Scott R. Bullock

ATI Course Schedule: http://www.ATIcourses.com/schedule.htm
ATI's Wireless Communications: http://www.aticourses.com/wireless_communications_spectrum_design.htm

Wireless Communications & Spread Spectrum Design
March 24-26, 2009
Beltsville, Maryland
$1490 (8:30am - 4:00pm)
Course Outline
quot;Register 3 or More & Receive $10000 each
Off The Course Tuition.quot;
1. Transceiver Design. dB power, link budgets,
system design tradeoffs, gains/losses, Signal-to-Noise,
Probability of Error, Bit Error Rate, Eb/No, link margin,
Summary tracking noise and signal level through a complete
system, effects and advantages of using spread
This three-day course is designed for wireless
spectrum techniques.
communication engineers involved with spread
2. Transmitter Design. Various types and system
spectrum systems, and managers who wish to enhance
designs of spread spectrum transmitters, PSK, MSK,
their understanding of the wireless techniques that are
QAM, OFDM, Other, Pseudo-Random code generator,
being used in all types of communication systems and
multiple access TDMA/CDMA/FDMA, antenna sizing,
products. It provides an overall
transmit/receive, local oscillator, upconverters,
look at many types and
sideband elimination, power amplifiers, standing wave
advantages of spread
ratios.
spectrum systems that are
designed in wireless systems 3. Receiver Design. Dynamic range, image
today. This course covers an rejection, limiters, minimum discernable signal,
intuitive approach that provides superheterodyne receivers, importance of low noise
a real feel for the technology, amplifiers, 3rd order intercept point for intermodulation
with applications that apply to products, two tone dynamic range, tangential
both the government and sensitivity, phase noise, mixers, spurious signals,
commercial sectors. Students filters, A/D converters, aliasing and anti-aliasing filters,
will receive a copy of the digital signal processors DSPs.
instructor's textbook, Transceiver and Systems Design 4. Automatic Gain Control Design & Phase Lock
for Digital Communications. Loop Comparison. AGCs, linearizer, detector, loop
filter, integrator, using control theory and feedback
systems to analyze AGCs, PLL and AGC comparison.
Instructor
5. Demodulation. Demodulation and despreading
Scott R. Bullock, P.E., MSEE, specializes in Wirelss techniques for spread spectrum systems, pulsed
Communications including Spread Spectrum Systems matched filters, sliding correlators, pulse position
and Broadband Communication Systems for both modulation, CDMA, coherent demod, despreading,
government and commercial. He holds numerous carrier recovery, squaring loops, Costas and modified
patents in communications and published several Costas loops, symbol synch, eye pattern, inter-symbol
articles in various trade magazines. He was active in interference, phase detection, Shannon' s limit.
establishing the data link standard for GPS SCAT-I
6. Basic Probability and Pulse Theory. Simple
landing systems and developed spread spectrum
approach to understanding Probability, Gaussian
landing systems for the government. He is the author of
process, quantization error, probability of error, bit error
two books, Transceiver and System Design for Digital
rate, probability of detection vs probability of false
Communications & Broadband Communications and
alarm, error detection and correction, digital pulsed
Home Networking, Noble Publishing. He has published
systems, pseudo-random codes for spread spectrum
numerous technical articles, is an adjunct professor at
systems.
ITT and a guest lecturer for Polytechnic University on
7. Multipath. Specular and diffuse reflections,
Direct Sequence Spread Spectrum and Multiple Access
Rayleigh criteria, earth curvature, pulse systems,
Technologies.
vector and power analysis.
8. Improving the System Against Jammers. Burst
What You Will Learn jammers, digital filters, adaptive filters simulations and
actual design results, quadrature method to eliminate
• How to perform link budgets for types of spread
unwanted sidebands, orthogonal methods to reduce
spectrum communications?
jammers, types of intercept receivers.
• How to evaluate different types of wireless
9. Global Navigation Satellite Systems. Basic
communication transceivers?
understand of the Global Positioning System GPS and
• What methods are used for spread spectrum
the spread spectrum BPSK modulated signal from
modems, multiple access, OFDM, error detection
space, Satellite transmission, signal structure, GPS
/ correction for digital communication systems?
receiver, errors, narrow correlator, selective availability
• What is multipath and how to reduce multipath SA, carrier smoothed code, Differential DGPS, Relative
and jammers? GPS, widelane/narrowlane, carrier phase tracking
• What is a Global Positioning System? KCPT, double difference.
• How to solve a 3 dimension Direction Finding 10. DF & Interferometer Analysis. Positioning and
system using interferometry? direction finding using a simpified interferometer
From this course you will obtain the knowledge analysis, direction cosines, basic interferometer
and ability to evaluate and develop the system equation, three dimensional approach, antenna
design for wireless communication digital position matrix, coordinate conversion for moving
transceivers including spread spectrum systems. baseline.

Register online at www.ATIcourses.com or call ATI at 888.501.2100 or 410.956.8805 Vol. 95 – 43

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Digital vs. Analog Comms
Digital System
Digital
5V 5V
PSK, FH, etc.
Demod
A/D Mod Sampler D/A

5V analog = Digital 101 LO LO Digital 101 = 5V analog

Perfect Reconstruction of the Digital Waveform Assuming No Bit Errors

Analog System

AM/FM etc
Demod
Mod

LO LO 1
Analog Analog + Noise
Bullock Engineering Research Copyright 2008

Digital Modulation

2


FSK and MSK Spectrums

MSK

Reduce Frequency Separation or Increase the Frequency Minimum Shift Key Rate - MSK
3


Continuous Phase - Phase Shift
Keying CP-PSK
Sinusoidal transitions from one phase state to another
•

No zero crossing, No AM
•

Remains at a phase state for a period of time
•

Used for packet radio and other burst type systems
•

Minimum Spectral Re-growth due to non-linearities
•

+90
+45
+135
0
R 0,0
Q Channel
1,0
R

180 I Channel 0
1

R R
Q
1,1
1 0,1
-135 -45
-90
4


Spectral Re-growth

Output of
Modulator

Filtered
Output
Sidelobes
Reduced

Spectral
Re-growth
(Sidelobe
Regeneration)
5


Practical Digital Waveform
Impulse Response
Ideal filter is the Sinx/x which is impossible to build These filters approx.
this ideal filter

Sinx/x

Raised Cosine

Raised cosine
squared

MSK
Gaussian Filter

6


Direct Sequence Spread
Spectrum Jammer

Fast PN
Signal Code
Jammer
Spread
Spectrum
Signal
Signal
Spread Spread
Spectrum Spectrum
Spreader Receiver

Fast PN
Code
Jammer
Signal

Filter
Signal Spread Jammer
Spectrum
despreader
7


FH Spread Spectrum
Jammer

PN Hopping Spread Spectrum Signal
Signal Spread Spectrum Signal
Synthesizer Jammer

Spread Spread
Spectrum Spectrum
Spreader Receiver

PN
Spread Spectrum Signal Spread Spectrum Jammer
Dehopping
Jammer Signal
Synthesizer
Filter

Spread
Spectrum
despreader
8


Multiple User Techniques
System 1 System 2 System 3

1 2 3 1 2 3
time
a. Time division multiple access
.

Code 1 System 1

System 2
Code 2
System 3
Code 3

b. Code division multiple access.

f1 f2 f3

Frequency
System 1 System 2 System 3

9
c. Frequency division multiple access.


Costas Loop

Signal 1

Signal 2

10


OFDM Spectrum
1.2
1
Amplitude

0.8
Channel 2
0.6 Channel 3
0.4 Channel 1
0.2
0
-10 -5 0 5 10
Frequency

11


Chapter 3 The Receiver

Superheterodyne
To
Digital
Processor
Image T/R Power A/D
IF BPF LPF
IFAmp
Limiter LNA
Reject Switch Divider Converter
Filter

LO AGC LO

Transmitter

12


Phase Noise, Log-Log Scale
Short term frequency/phase instability

Random walk FM 1/(f*f*f*f)
So(f)
dBc
Flicker FM 1/(f*f*f)
So(f) = power spectral density white FM 1/(f*f)
(radians2/Hz) dBc/Hz Flicker noise 1/f
white noise f

1 10 100 1 kHz 10 kHz
Frequency

1/(f*f*f*f) = close to carrier, difficult to measure, vibration, shock, temperature, environmental.
1/(f*f*f) =, observable in high quality oscillators, masked in low quality oscillators, not fully
understood, physical resonance mechanism or actual parts in the oscillator.
1/(f*f) = common in passive-resonator like cesium and rubidium standards.
1/(f) = transistors, amplifiers, etc., noisy electronics, LNA helps.
f = produced like the 1/f noise, stages of amplification is mainly responsible, broadband noise.
13


Group Delay
Linear
Receiver

Constant Group Delay

ISI Dispersion
Non-
Linear
Receiver
Non-Constant Group Delay

14


Group Delay Compensator

Filter Response ______

Constant Group Delay Filter Group _______
Delay
Group Delay ______
Compensator

15


Aliasing

ts ts ts ts ts
Sample points in time

Waveform is sampled at the Nyquist rate
Estimated Frequency
Waveform does not meet Nyquist criteria
Alias frequency produced by under-sampling the high frequency
16


Control Theory Analysis and
Root Locus Plot

17


AGC/PLL Comparison
V/dB filter DC offset gain 1/S dB/V
dBm + dBm
Kd F(s) Threshold Integrator Ko
Kc

- dB Amp control curve

a. AGC control system analysis block diagram.

V/phase filter no offset gain phase/V
phase phase
+ error Threshold
Ko/S
Kd F(s) Kc
=0
-
VCO control curve
phase

b. PLL control system analysis block diagram.

18


Bode Plot for Negative
Feedback Systems
+20dB

Gain
0dB
-10 dB

-1000
Phase
-1800

-2700

Frequency (log scale)

Instability & oscillation criteria for negative feedback systems, 0dB Gain, -1800 phase shift

Gain Margin (-1800 phase shift) = 0dB – (-10dB) = 10 dB

Phase Margin(0dB gain) = -1000 – (-1800) = 800
19


Cascaded PN-code Matched Filters for
Increased Process Gain and Margin
11 1 11 1 1 11 1
-1 -1 -1
-1-1 -1 1 delay 1 delay 1 delay 1 delay
1 -1 1 1
1 -1 1 1
PN- Code
1 1 1 1

44 4
sum

1 delay 1 delay 1 delay 1 delay
Additional PN- Code 4 -4 4 4
(Or retrieve data direct) 1 -1 1 1
-4
4 4 4 4

sum 16
4
4
4
4
Position of Pulse output
provides data information
20


Comparison between Absolute
and Differential PPM
Data Lost
Reference Pulse
TOA Pulse 1 TOA Pulse 3
TOA Pulse 2
..
Dead Time
Dead Time Dead Time

t0 t1 t2 t3
t0 t1 t2 t3 t4 t5 t6 t7
t0 t1 t2 t3 t4 t5 t6 t7
Time Slots of PPM
No Pulse detected Time Slots of PPM
in Time Slots Data output 000
Data output 011
No Data Output

Absolute PPM
Data Lost
Data Lost
TOA Pulse 2
Reference Pulse TOA Pulse 1
TOA Pulse 3
No Dead Time
Dead Time Dead Time
No Time Slots of PPM

t0 t1 t3 t4 t5 t6 t7
t0 t1 t3 t4 t5 t6 t7 t2
t2 t0 t1 t2 t3
No Pulse detected Received Pulse ok but Time Slots of PPM
in Time Slots No time reference Data output 000
No Data Output No Data output
But Provides reference
For next pulse

Differential PPM
21


Coherent vs Differential
Bit Errors
Bit error

Sent digital data 11 0 1 011 0 111 000 1 0 1 0
Received digital data 11 0 1 011 1 111 000 1 0 1 0
One Received data error
Coherent System

Bit error

Sent digital data 10 1 1 1 10 1 100 100 1 1 1 1
Received digital data 10 1 1 1 10 0 000 100 1 1 1 1
Two Received data errors
Differential System

22


Sliding Correlator

23


Intersymbol Interference (ISI)
One received symbol interfering with adjacent received symbols
•
Caused by Dispersion
•
– Pulse stream/pulse consists of many frequencies – Fourier
Series/Transform
– Frequencies propagate at different delays – non-constant group delay
ISI
Dispersion
Non-
Linear
Receiver
Non-Constant
Group Delay

Vh = highest Vpeak center of the eye.
Vl = lowest Vpeak center of the eye.

ISI = -20log(Vh/Vl)
24


CDF Equation For Gaussian
Distribution
Probability Density Function for Gaussian Distribution Cumulative Distribution Function for Gaussian Distribution

x = -1  x = +1  1 or 100%
Fx (x) CDF
Probability of
Occurrence .159
95.4%.
.023
x=-2 x = +2  fx (x) for x = -1 
fx (x) for x = -2 
Value x

f

Fx(x) = 1/2[1+erf(x/( 2 ))], mean = 0
•
Fx(x) = 1/2[1+erf(-2/( 2 ))]
•
=1/2[1+erf(- 2 )]
–
– erf(-x) = -erf(x), -erf(1.414) = -.954
– Fx(x) = 1/2[1- .954] = .023
– Probability +/- 2 = 2*.023 =.0456
– Probability inside curve = 1-.0456 = .954 = 95.4%.
25


Probability of Error Curves
1.00E+00

1.00E-01

1.00E-02

Coherent BPSK
1.00E-03 Coherent QPSK
Pe

DPSK
Coherent FSK
1.00E-04
NonCoherent FSK

1.00E-05

1.00E-06

1.00E-07
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9

Eb/No (dB)

26


Probability of Detection and
False Alarms Curves
Cumulative distribution function determines probabilities of one sided
•
noise and S+N gaussian probability density functions
– CDF from the right – sum probabilities from the right.
0 1.00E+00 0.00102259 #NAME? #NAME? 1 5 6.99 7.78
0.1 1.20E+00
9.97E-01 1.34E-03 #NAME? #NAME? 1 5 6.99 7.78
0.2 9.89E-01 1.75E-03 #NAME? #NAME? 1 5 6.99 7.78
Threshold Pfa Pd
0.3 1.00E+00
9.76E-01 2.28E-03 #NAME? #NAME? 1 5 6.99 7.78
0.4 9.57E-01 2.94E-03 #NAME? #NAME? 1 5 6.99 7.78
Probability of Occurance

0.5 9.33E-01 3.78E-03 #NAME? #NAME? 1 5 6.99 7.78
0.6 8.00E-01 Noise
9.06E-01 4.83E-03 #NAME? #NAME? 1 5 6.99 7.78
Signal + Noise 5
0.7 8.74E-01 6.14E-03 #NAME? #NAME? 1 6.99 7.78
0.8 6.00E-01
8.38E-01 7.76E-03 #NAME? #NAME? 1 5 6.99 7.78
0.9 8.00E-01 9.76E-03 #NAME? #NAME? 1 5 6.99 7.78
1 4.00E-01
7.59E-01 1.22E-02 #NAME? #NAME? 1 5 6.99 7.78
1.1 7.17E-01 1.52E-02 #NAME? #NAME? 1 5 6.99 7.78
1.2 6.73E-01 1.87E-02 #NAME? #NAME? 1 5 6.99 7.78
1.3 2.00E-01
6.28E-01 2.30E-02 #NAME? #NAME? 1 5 6.99 7.78
1.4 5.83E-01 2.82E-02 #NAME? #NAME? 1 5 6.99 7.78
1.5 0.00E+00
5.38E-01 3.43E-02 #NAME? #NAME? 1 5 6.99 7.78
0
0.6
1.2
1.8
2.4
3
3.6
4.2
4.8
5.4
6
6.6
7.2
7.8
8.4
9
9.6
10.2
10.8
11.4
12
12.6
13.2
13.8
1.6 4.94E-01 4.14E-02 #NAME? #NAME? 1 5 6.99 7.78
1.7 4.51E-01 4.98E-02 #NAME? #NAME? 1 5 6.99 7.78
Energy

27


FEC Code Generation
n bit code word
Block
k Information Bits
n = Block Length
Encoder

Maps k information bits
into an n-symbol output block

Block Codes (Hamming, Cyclic, Reed Solomon Codes)
Figure 6.7.2.2a Block Codes (Hamming, Cyclic, RS Codes)

XOR

Tapped Delay Line
Output Symbols
Information
1234567 Two times the
Input Bits
Input Rate
7-bit shift Register switch

XOR

•Convolutional code, rate ½, constraint length 7
Figure 6.7.2.2b Rate 1/2 Convolutional Encoder
28


Example of Generating a Linear
Systematic Block Code (7,4)
Generator Matrix Message Modulo-2
(1000011) 1 (1000011)
(0100110) 0
(0010111) 1 (0010111)
(0001101) 0
Systematic Code Word =(1010100)
–4 bits of data Identity Matrix
Messages Codewords (7,4)
–3 parity bits (0000) (0000000)
(0001) (0001101)
(0010) (0010111)
(0011) (0011010)
(0100) (0100110)
(0101) (0101011)
(0110) (0110001)
(0111) (0111100)
(1000) (1000011)
(1001) (1001110)
(1010) (1010100)
(1011) (1011001)
(1100) (1100101)
(1101) (1101000)
(1110) (1110010)
(1111) (1111111) 29


Error Correction
H-T
Error Vector Coset, error vectors
e6,e5,e4,e3,e2,e1,e0 * 011 0 e6 e6 1000000
110 e5 e5 0 0100000
111 = e4 e4 e4 0010000
101 e3 0 e3 0001000
100 e2 0 0 0000100
010 0 e1 0 0000010
001 0 0 e0 0000001
e5+e4+e3+e2 = 0
e6+e5+e4+e1 = 0
e6+e4+e3+e0 = 1
0 0 1
3 equations, 7 unknowns (7-3=4), possible solutions = 24
Solve for a solution with the most zeros = all zeros except for e0 = 0000001
e6=e5=e4=e3=e2=e1=0 and e0 = 0000001 satisfies the three above equations with most zeros
Correct Code sent = 1010100
Vc = r+e = 1010101+ 0000001 = 1010100 Corrected bit in code word

30


Trellis Diagrams



1st merge, need to make a decision
 2 possible paths






Constant Mod hi = 1/4


 1st merge







Multi-h [1,2/4], [hi] = [1/4,2/4] 31


Turbo Codes
Turbo Encoder
Mux Parallel/Serial
PAD Turbo Encoded Output
Information Bits
Puncturing
PAD appends n – k tail bits
for all zeros state, x0 Encoder 1 Recursive Systematic Code Generator

Interleaver Encoder 2
+
Input Z-1 Z-1 Z-1 Z-1

+

Turbo Decoder

De-Mux
Turbo Encoded Decoder 1 Interleaver Decoder 2 De-Interleaver Estimated
Serial/Parallel
Input Sequence
Insertion
De-Interleaver

32


Diffuse Reflection over a
Glistening Surface
Receiver

R

hr
Reflected rays
Off Glistening Surface
Transmitter

ht

Glistening
Surface

33


Antenna Diversity

34


Quadrature GSO System
OMNI Antenna
(Jammer only) Jammer Only
I
PD
PD

0 wi
int
PD LO

90
- I signal out
error i
Q
+

Directional Antenna
(Signal + Jammer) Jammer Only
PD
PD

0
wq
int
PD LO

90
- Q signal out
error q
+

35


Wideband Adaptive Filter
10 dB
High Freq Wideband
Wideband + Narrowband Signal Only
-10 dB Narrowband
Signal Estimate -10 dB -10 dB
Signal
Residual
10 dB 10 dB
Synthesizer Narrowband
Signal
LO
BPF

BPF
10 dB
BPF
30 dB
BPF BPF
o o
0 -90
4-port
10 dB PD

LPF
LPF LPF

30 dB 30 dB 15 dB 15 dB
15 dB
Update shared weights

Digital
LPF
Q-channel Filter

Digital
LPF
Filter
I-channel
15 dB
LMS

36


GPS Landing Systems

D8PSK LPI/Anti-jam Data Link
Sends GPS Corrections

37
Relative GPS for moving platforms (Aircraft Carriers)
Bullock Engineering Research Kinematic Carrier Phase Tracking KCPT for CATIII landing systems Copyright 2008

Need to Provide a Military
Communications Network

MILCOM

38


Interferometer

Antenna 1
Phase 1

INTERFEROMETER
Baseline

Phase 2

Antenna 2

Measures the phase difference between two antennas
39


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