SPREAD SPECTRUM SYSTEMS
WITH
COMMERCIAL APPLICATIONS
ROBERT C. DIXON
SUMMARY
The spread spectrum world has changed radically since the last edition of this
classic professional resource was published. Now military applications have levelled
off commercial applications have taken of and numerous consumer products are in
development. This new edition keeps you right up to date with…
A complete new section on commercial applications-featuring direct
·
sequence versus frequency hopping operation below ambient noise level
error correction coding near-far performance linear signal requirements and
synchronozation
·
Full treatment of CDMA-including the number of signals to a band-windth
frequency division multiplex time-division multiplex code division multiple access
receiver sensitivity multipath rejection direct sequence fading rate and more
·
Coverage of relevant FCC regulations- presenting excerpts from FCC regulations concerning spread spectrum and low-power
operation in the ISM bands a summary of Part 15 of the Spread Spectrum Rules and a discussion of spread spectrum operation by
radio amateurs
·
Details on current consumer and commercial systems
Essential to the next generation of mobile cellular cordless and other personal communications systems… vital to the future of
communications data transmission message privacy signal hiding and position location spread spectrum technology has never been
so important to professionals in the field.
CONTENTS
PART I GENERAL SPREAD SPECTRUM SYSTEMS
1
1
3
The Whats and Whys of Spread Spectrum Systems
1.1
1.2
1.3
2
3
9
10
Spread Spectrum Techniques
18
2.1
Direct Sequence Systems
Characteristics of Direct Sequence Signals
Radio-Frequency Bandwidth in Direct Sequence Systems
Direct Sequence Process Gain
Direct Sequence Code and Spectrum Relationships
The Minimum Shift Key Technique
Frequency Hopping
Characteristics of Frequency Hopping Signals
Determining Frequency Hopping Rate and Number of Frequencies
Avoiding the Repeat Jammer
18
19
24
28
30
31
32
32
36
44
2.3
Time Hopping
46
2.4
Pulsed FM (Chirp) Systems
Characteristics of Chirp Signals
Hybrid Forms
Frequency Hopped/Direct Sequence Modulation
Time-Frequency Hopping
Time-Hopping Direct Sequence
48
48
50
51
55
56
2.2
2.5
3
What Is a Spread Spectrum System?
Why Bother?
Process Gain and J amming Margin
Coding for Communications and Ranging
60
3
Coding for Communications and Ranging
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
4
114
4.1
115
123
123
126
126
128
132
138
141
143
143
145
146
148
155
4.3
Balanced Modulation
Effects of Carrier and Code-Rate Spurious(Lack of Suppression)
Quadriphase Modulation
Carrier Modulation Trade Offs
Effect of Synch Acquisition
Sidelobe Energy Output
Frequency Synthesis for Spread Spectrum Modulation
Indirect Synthesis
Synthesis from Digital Words
Sending the Information
Carrier Modulation
Clock Rate Modulation
Code Modification
Digitizing Methods
Frequency Hopping Code Modifiers
Correlation and Demodulation
159
5.1
159
160
162
164
168
174
177
188
192
193
198
198
202
204
205
209
211
216
5.2
5.3
6
62
64
65
67
70
70
77
85
85
89
90
91
93
98
103
105
109
110
Modulation and Modulators: Generating the Wideband Signal
4.2
5
Maximal Sequences
Run-Length Distribution
Autocorrelation
Linear Addition Properties
State Exhaustion
Linear Code Generator Configuration
Autocorrelation and Cross-Correlation of Codes
Composite Codes
Gold Code Sequence Generators
Syncopated-Register Generators
JPL Ranging Codes
Chip Rate and Code Length
Choosing a Linear Code
Generating High Rate Codes
Software-Implemented Codes
Code Selection and Signal Spectra
Code Baseband Spectra
Error Detection and Correlation Codes
60
Remapping the Spread Spectrum
ln-Line Correlation
Heterodyne Correlation
Code Timing Effects on Correlation
Effect of Nonsynchronous Input Signals
Correlator Output with Interference
Direct Sequence Reaction to Interference
Frequency Hopping Reaction to Interference
Baseband Recovery
Phase- Lock Loops
Squaring Loops
Costas Loop Demodulation
Frequency Modulation Feedback Demodulators
PDM Demodulation
Frequency Hopping Demodulation
Integrate-and-Dump Filters
The Dehopped Signal
M-ary Detection
Synchronization
220
6.1
220
222
224
227
228
230
232
232
233
233
235
240
254
254
259
6.2
Sources of Synchronization Uncertainty
Initial Synchronization
The "Sliding" Correlator
Synchronization Preambles
Frequency Hop Synchronization
Transmitted-Reference Methods
Universal Timing
Burst Synchronization
Sequential Estimation
Special Coding for Synch Acquisition
Matched-Filter Synchronizers
Synch Recognition
Tracking
Tau-Dither Tracking
Delay-Lock Tracking
Delay-Lock Tracking
Coherent Carrier Tracking
Split-Bit Tracking
Coherent Loss Due to Bandpass Filtering
7
The RF Link
267
7.1
7.2
7.3
268
272
278
278
280
280
281
285
285
287
289
289
290
291
291
295
7.4
8
Noise Figure and Cochannel Users
Dynamic Range and AGC
The Propagation Medium
Line-of-Sight Loss
Adsorptive Losses
DifferentiaI Phase Delay
MuItipath
Overall Transmitter and Receiver Design
The Transmitter
Power Amplification
VSWR
Receiver RF Considerations
Receiver Signal Handling Capacity
Wideband Front Ends
The Ideal RF Section
Bandwidth and Phase-Shift Effects
Navigating with Spread Spectrum Systems
297
8.1
297
301
302
304
304
306
307
312
312
8.2
9
Ranging Techniques
Tone Ranging
Sources of Range Error
Frequency Hopping Range Measurement
More on the Selection of a Clock Rate
Selecting the Ranging Code
Hybrid-Ranging System
Direction Finding
Special Antennas
Applications of Spread Spectrum Methods
Space Systems
Avionics Systems
Test Systems and Equipment
Message Protection
Position Location
Real Systems
10
259
260
263
264
Test and Evaluation of Spread Spectrum Systems
319
319
330
335
338
338
340
341
Sensitivity
Selectivity
Jamming Margin
341
343
344
Synch Acquisition
Loss of Synchronization
Signal-to-Noise Ratio vs. Interference Level
346
346
347
Process Gain
On Testing Spread Spectrum Systems to Determine Their Process Gain
The FCC Method
Cross Correlation
Transmitter Measurements
General
347
348
352
352
353
355
PART Il COMMERCIAL APPLICATIONS OF SPREAD SPECTRUM SYSTEMS
359
11
361
Tradeoffs in Commercial Applications of Spread Spectrum Systems
11.1
11.2
Excerpt from FCC Regulations Concerning Spread
Spectrum and Low Power Operation in the ISM
Bands
Summary of Part 15 Spread Spectrum Rules
Spread Spectrum Operation by Radio Amateurs
Comparison of Military and Commercial Advantages
of Spread Spectrum
Direct Sequence Versus Frequency Hopping
Range Resolution
Interference to Other Systems
Operation Below Ambient Noise Level
Error Correction Coding
Near-Far Performance
361
365
365
366
367
368
368
370
371
374
11.3
11.4
11.5
11.6
11.7
12
14
374
375
375
375
376
377
378
380
383
383
386
386
387
391
392
392
394
395
396
397
Multiple Access Snake OH and Fairy Tales
399
12.1
399
399
402
404
406
409
410
412
414
12.2
13
Near-Far Performance
Linear Signal Requirements
Synchronization
Conclusion
Frequency Hopping in Commercial and Consumer
Applications
Frequency Hopping Systems Interfere with Other Users
Over a Longer Distance
Self- Interference
Just What Is Jamming Margin?
Multipath Rejection and Spread Spectrum Signals
Direct Sequence
Frequency Hopping
Fading Rate
Frequency Division in Spread Spectrum Applications
Use of Spread Spectrum Signals in Conjunction with Conventiona1 Cellular
Telephone Signals A Workable Example of Spread Spectrum Overlay
Spread Spectrum Telephone Characteristics
Cellular IFH Overlay
Cellular IDS OverIay
Interference from Cellular Towers
Operation of Spread Spectrum Microcell Receiver Onside Building)
Interference from 7 Watt Mobile Cellular Telephones
The Number of Signals in a Bandwidth
Frequency-Division Multiplex
Time-Division Multiplex
Code-Division Multiple Access
Summary-Bits Is Bits or There Is No Magic (Too Bad)
Receiver Sensitivity in COMA Systems
COMA and Jamming Margin
Frequency Hopping and COMA
COMA and "Soft" Handoff
Current Consumer and Commercial Systems
416
Global Positioning System Receivers
Personal Communications
Vehicle Location Systems
417
420
422
Local Area Networks
Sure-Comm Voice System
423
424
Turning the (Spread Spectrum) World Upside Down
426
14.1
14.2
The PCS Idea
Choices in PCS Design
Operating Band
Signal Format
The Capacity Game
Average Data Rate
Sectorization
The Impact of "Capacity"
Today's Needs
A Final Word
427
429
429
430
430
430
431
431
432
432
Appendix 1
Glossary of Terms
434
Appendix 2
Bibliography on Spread Spectrum Systems and Related Technology
440
Appendix 3
Equivalence of Simple and Modular Sequences
485
Appendix 4
Multiplication of Direct Sequence Signals
487
Appendix 5
Linear Code-Sequence Vulnerability
489
Appendix 6
The Relation Between W N and w 3 dB
495
Appendix 7
Gold Code Selection
500
Appendix 8
Typical Error Correction Coding Integrated Circuits
504
Appendix 9
Typical Integrated-Circuit Frequency Synthesizers
512
Appendix 10
Report on Spread Spectrum and Other Interference with Respect to its Effect
on Standard Microwave Communications Links
521
Answers to Problems
557
Index
569
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