NCJ Number
11423
Date Published
1973
Length
141 pages
Annotation
RESULTS OF A ONE-YEAR TECHNICAL STUDY OF DIGITAL DATA TRANSMISSION OVER LAND-MOBILE RADIO CHANNELS.
Abstract
THERE HAS BEEN CONSIDERABLE ACTIVITY OVER THE PAST FEW YEARS IN THE DEVELOPMENT AND TESTING OF VEHICLE PRINTERS AND TWO-WAY DATA TERMINALS FOR USE IN LAW ENFORCEMENT MUCH OF THE REPORT IS DEVOTED TO DESCRIPTION AND ANALYSIS OF THE TWO MAJOR PROBLEMS OF THE RADIO CHANNEL-MULTIPATH FADING AND AMBIENT IMPULSIVE NOISE - AND THEIR RELATIVE EFFECTS ON ERROR RATES FOR VARIOUS TYPES OF DATA MODULATION. IT IS CONCLUDED THAT MULTI-PATH FADING IS THE DOMINANT LIMITATION AND THAT BOTH SPACE AND FREQUENCY DIVERSITY TRANSMISSION SHOULD BE INVESTIGATED AS A MEANS OF COMBATTING ITS EFFECTS AND IMPROVING THE RELIABILITY OF HIGH-SPEED DATA TRANSMISSION. A DATA RATE OF 2,0002,400 WORDS PER MINUTE IS SUGGESTED AS A REASONABLE GOAL FOR LAW ENFORCEMENT DIGITAL COMMUNICATIONS, BOTH TO SPEED UP CALL-RESPONSE CYCLES AND INCREASE CHANNEL CAPACITY AS COMPARED TO VOICE TRANSMISSION. OTHER TOPICS DISCUSSED ARE CODING FOR ERROR DETECTION AND CORRECTION, OPERATIONAL AND SPECTRUM UTILIZATION ISSUES, THE ROLE OF PORTABLES IN A DIGITAL WORLD, AND ECONOMIC FACTORS. INFORMATION AND VIEWPOINTS GAINED IN DISCUSSIONS WITH EQUIPMENT MANUFACTURERS AND POLICE DEPARTMENTS AND A GLOSSARY OF TERMS ARE CONTAINED IN SEVERAL APPENDICES. (AUTHOR ABSTRACT MODIFIED) (SNI ABSTRACT)