Spectrum Management System

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					         Montana
 Department of Administration


       Information
         Services
         Division




 Spectrum
Management
  System
        October 28, 1996

           Produced
              by
          GeoSpectrum, Inc.
            1821 Choteau
         Helena, MT 59601
             gsi@MT.net
           (406) 443-6576



                                i
TABLE OF CONTENTS


INTRODUCTION                                                             1



GENERAL NOTES                                                            1

ARCVIEW’S CONCEPT                                                        1
ARCVIEW USER INTERFACE ADDITIONS                                         2

PROJECT MANAGEMENT                                                       4



PROPAGATION STUDY MANAGEMENT                                             4



PROPAGATION MODELING                                                     6

PROPAGATION PARAMETERS                                                   6
CATALYST FILE                                                            9
CONTOUR SELECTION                                                       10
GAIN COUPLING                                                           10
ANTENNA FILES                                                           11
COMMAND LINE EXECUTION                                                  12

APCO DATABASE INTEGRATION                                               12

PROCEDURE                                                               13

PROGRAMMING NOTES                                                       13



APPENDICES                                                              14

APPENDIX A
RADIO PROPAGATION ABOVE 40 MC OVER IRREGULAR TERRAIN - THE EGLI MODEL
APPENDIX B
NTIA DEFINITIONS AND RELATIONSHIPS OF TELECOMMUNICATION SYSTEM TERMS
APPENDIX C
SOFTWRIGHT TAP TIPS: CALCULATING TALK-OUT AND TALK-BACK
MOBILE RADIO TECHNOLOGY: FIELD INTENSITY FORMULAS AND THEIR USE

                                                                         i
Figures
Figure 1 - User Interface Additions.................................................................................. 2
Figure 2 - SMS Menu ...................................................................................................... 3
Figure 3 - Directory Hierarchy ......................................................................................... 3
Figure 4 - Propagation Study Manager ........................................................................... 5
Figure 5 - Catalyst File Management .............................................................................. 5
Figure 6 - Intermediate File Management ....................................................................... 5
Figure 7 - Study Fileset Management ............................................................................. 5
Figure 8 - Modeling Parameters Input ............................................................................. 6
Figure 9 - Sample Antenna Data File ............................................................................ 11
Figure 10 - Command Line Usage ................................................................................ 12
Figure 11 - APCO Site Data Refresh............................................................................. 13



Tables
Table 1 - Antenna and Gain Factor Applicability............................................................. 7
Table 2 - Propagation Parameters Details ...................................................................... 8




                                                                                                                          ii
Introduction

        The ISD Spectrum Management System (ISD-SMS) is a hybrid software tool, combining
a commercial off-the-shelf geographic information system (GIS) package with custom
propagation modeling and transmitter site data import libraries. Environmental Systems Research
Institute, Inc., (ESRI) provides ArcView® 3.0, a 32-bit GIS package. ArcView provides a host
of sophisticated spatial analysis tools presented through a graphical user interface optimized for
Win32 operating systems (Windows 95 and NT). GeoSpectrum, Inc., (GSI) provides the
dynamic link library (DLL) extension to ArcView that makes propagation modeling an integral
part of the GIS. GSI also provides a special, highly compressed terrain database and ArcView
Avenue® program scripts that further extend the package.


General Notes

        The Spectrum Management System preserves all features of ArcView. It produces
propagation model and site databases layers in ArcView’s native formats: shapefiles, indexes, and
xBase-standard attribute files. Though other data formats can be displayed and manipulated with
ArcView, none are as fast and flexible as these native formats.
        As provided to ISD, the SMS includes a number of cosmetic layers - layers used for
display/reference purposes - that have been derived from Montana State Library sources. The
Natural Resources Information Systems (NRIS) office of the State Library provided county
boundary, highway, waterways, 1 km Digital Elevation Model (DEM), and other layers in both
projected and unprojected forms, necessary for different purposes as discussed below. National
and international layers are provided by ESRI in its ArcView distribution. A statewide 3” DEM
for Montana has been created by GSI directly from USGS sources and is included, as well.

ArcView’s Concept
        ArcView conceptually organizes all of its offerings into projects. Only one project can be
active at any time and all information describing the project - including which windows were left
open, what the different user interfaces look like, which data sources fill themes, what user
graphics have been drawn on the screen, and much more - is stored in a text file of the form
projectname.apr where projectname is that given by the user. This file can be browsed and even
edited, but great care must be taken since its structure is complex.
        The SMS is packaged as an ArcView project whose components can be copied and
renamed into an endless number of customized projects. The “Project Management” section
below contains further details.
        From the basic map display, the user can put all of ArcView’s powerful geographic
analysis tools to work. These tools are what separate a true GIS from a simple mapping program.
The SMS extensions specifically add capabilities for incorporating FCC site data as provided by
APCO and interactively creating georeferenced site coverage map layers. These data layers can
be used for displays and paper maps, but more importantly they can be used in sophisticated
analyses to answer questions such as, “How many miles of secondary highway are within the 100
dB loss contour of this site?”, or “What’s the population density within this contour?”

                                                                                                 1
         ArcView User Interface Additions
                The standard user interface of ArcView is preserved throughout each of its
document types: Views,
Layouts, Tables, Charts,                       Select tool         Propagation tool
and Scripts. SMS                                                                       SMS Menu
functionality is contained
within a single drop down
menu, an enhanced View
‘Select’ tool, and a new
tool on the View toolbar for
initiating propagation
studies. The SMS menu
appears on the Project,
View, and Script user
interfaces. Figure 1 shows
additions to the View user
interface.
         The standard View
‘Select’ tool has been
enhanced to display
latitude, longitude, and
elevation on the main
window status line
                               Figure 1 - User Interface Additions
whenever it is clicked on a
View display. This feature overcomes the low-resolution of ArcView’s interactive coordinate
display to the right of the View toolbar. It further provides ground elevation in meters above
mean sea level (AMSL), returning the value ‘-9999’ if no elevation data exists for that location.
Elevations are taken from the same GSI terrain files used for propagation studies.
         A new tool is provided to initiate study calculations by clicking on the View display. It
appears on the tool menu that contains graphics drawing choices. Details of its use are provided
in the “Propagation Modeling” section below.
         Four choices are provided on the common SMS menu:

          Show Project Dictionary
             Displays the project dictionary and global variables

          Manage Propagation Studies
             Provides the initial dialogue for managing propagation study files

          Set Propagation Parameters
              Provides a dialogue for selection of file parameters that determine whether
              existing intermediate files will be used when a propagation is initiated

          Refresh Site Data
              Provides a dialogue for selecting an input file for updating the FCC site database

                                                                                                     2
                                                                         Later sections
                                                                 explain selections on this
                                                                 menu The project
                                                                 dictionary is discussed
                                                                 under “Programming
                                                                 Notes”. “Propagation
                                                                 Study Management” and
                                                                 “APCO Database
                                                                 Integration” include
                                                                 explanations of the others.
                                                                         Figure 3 shows the
                                                                 SMS directory hierarchy.




  Figure 2 - SMS Menu
                                 MT-GSI Propagation terrain data (Montana),
                                        in 1 degree x 1 degree blocked files

                                 SMS Root directory for the Spectrum Management
                                     System, containing the standard SMS project file
                                     (sms.apr), a read-only back-up (sms_raw.apr), and
                                     user projects
                                    BIN    Binary code for the SMS, including the DLL,
                                           a command line executable version of the
                                           propagation program, and a list of error codes

                                    CODE       Copies of Avenue scripts used within the
                                               SMS, here saved as text files
                                    PERMDATA           Permanent geographic and attribute
                                                       data, including APCO sites
                                       ANTENNAS Directional antenna information
                                       INFO     ESRI database files associated with grid datasets
                                       RELIEF       Statewide, 1km Digital Elevation Model (DEM)
                                                    Arc/Info® grid format. Approximately 650 KB
                                       TERRAIN      Statewide, 3” Digital Elevation Model (DEM)
                                                    Arc/Info® grid format. Approximately 100 MB

                                    STUDIES         User area for propagation studies
                                    TEMPDATA            Volatile files that will be deleted
                                    TOOLS Various tools used within the SMS,
                                          including a sample catalyst file for batch
                                          calculations, ArcView legend files, sample
                                          FoxPro site data queries, and projection
Figure 3 - Directory Hierarchy            information on the NRIS reference layers

                                                                                                    3
Project Management

        The SMS with its standard user interface, Avenue scripts, and DLL extension are stored
as an ArcView project. This approach allows the user to customize their installation and even
save different versions for different purposes. One read-only copy of the standard project
(sms_raw.apr) is saved in the \Win32app\SMS subdirectory (see hierarchy above). It provides a
known starting point for new projects and helps prevent corruption of the SMS installation.
        Though ArcView’s approach to creating and saving projects is very flexible, projects can
grow and objects can be added of which the user may be unaware.. For this reason, it is
recommended that new projects be created by first loading sms_raw.apr and then copying it
under a new name, using the Save_As selection of the File menu.

        Six “views” are included in the standard project: Projected and unprojected views of the
world, the nation, and the state. Different data layers are included at each scale. The unprojected
views are provided so the 3” DEM layer can be viewed, analyzed, and contoured; ArcView is
unable to project raster-based data (such as the DEM) on the fly as it is able to do with raw
vector sources (e.g. highways). A projected version of the coarser, 1 km DEM is provided for
use at a state scale. Different views and projects share these reference data layers, so any
modification of one is bound to affect other views and projects.
        A special, compressed version of the 3” terrain database exists to speed propagation
modeling calculations. This data is stored in 1°x1° blocks in the \Win32app\mt-gsi subdirectory.
Though this results in a duplication of data to some extent 1, modeling is greatly speeded. The
run-length limited (RLL) encoding used by ESRI produces raster datasets 100% larger than those
produced by GSI. Modeling algorithms take advantage of available RAM to cache terrain blocks
rather than reading each elevation value separately from disk.


Propagation Study Management

        The ‘Manage Propagation Studies’ selection of the main ArcView SMS menu provides
choices to manage files created in the modeling process. That process begins either interactively
through application of the GUI propagation tool on a View display or by launching modeling
from the MS-DOS command line. Subsequent sections detail each approach. The catalyst file,
described fully on page 9, carries parameters to the modeling engine in either method.
        The modeling process is designed to save catalyst files, intermediate output data, and
ArcView shapefile sets upon completion. By default, the catalyst and ArcView files are saved
under sms\studies, while the intermediate terrain, loss, and azimuth/distance files go into
sms\tempdata where they can and will be deleted without harm. Figure 4 shows the initial
dialogue. Figures 5-7 show subsequent choices.
        Catalyst files are considered part of the study fileset, thus can be copied, renamed, and
deleted under two different dialogues. Use ‘Study Fileset Management’ when all files that make
up a particular study are to be manipulated. Use ‘Catalyst File Management’ when the input
parameter files alone are of interest.

1
    The ArcView grid and GSI terrain files are created directly from the same USGS source.

                                                                                                    4
Figure 4 - Propagation Study Manager                  Figure 6 - Intermediate File Management




Figure 5 - Catalyst File Management                   Figure 7 - Study Fileset Management

         The ‘Intermediate File Dialogue’ provides means to inspect, copy, rename, delete, and
otherwise clean up these by-products of propagation modeling. Over time, contour shapefiles will
be deleted from the sms\studies subdirectory while their original intermediate files are left in
sms\tempdata. This dialogue has a selection for cleaning out these orphaned files.
         The ‘Set Propagation Parameters’ dialogue from the main SMS menu provides global
control over how intermediate files are used. These file parameters are distinct from those set for
individual runs and are in effect under a given project until set differently. If multiple runs from
the same site are planned, selecting the option here for re-using terrain extraction files will reduce
runtime. Similarly, if the same site and transmit parameters are to be used, selecting the option to
re-use loss files simply causes a new set of loss contours to be generated from a prior run. In
either case, the study name is used to determine if any previous terrain and loss files exist.
         Unique study names should be used for each separate site and for different system
configurations. No coordinate or other parameter checking is done to insure reused intermediate
files are for the same site and configuration. When in doubt, model from scratch. In every case,
propagation modeling runs will be done entirely from scratch if intermediate files of the same
study name do not exist.

                                                                                                    5
Propagation Modeling

         In 1957, John Egli’s model was presented to the radio world as a plane earth model where
statistical variance was used to account for irregular terrain effects2.
         The Egli model originally used in the Arc/Info® version of ISD’s Spectrum Management
System was implemented by Communications Engineering Technology (CET) of New Smyrna
Beach, FL. It was found to be grossly flawed in several respects, including as a result of
programming errors. The Modified Egli Model, as CET referred to it, was overhauled by Dan
Hawkins, now principal of GeoSpectrum, Inc., while employed with ISD.
         This implementation was further refined by GSI and is presented in the ArcView SMS as
the Revised Egli Model. It includes shadow losses, earth curvature effects, and incremental
height above average terrain (HAAT) calculations, thus making it more of a rough earth model.
Egli’s standard location variability (50%) is employed in determining where contours lie and the
user is still referred to his publication for correction factors where other variability is desired3.
         All the various tools for propagation modeling and depiction are included in the single
SMS dynamic link library (DLL) attached to ArcView. When a user clicks on a map location
with the propagation tool, a dialogue below is presented for input of model parameters.


Propagation Parameters
         Model shapefiles, their
intermediate source files, and initial text
catalyst files are named according to the
“study name” input by the user. The
interactive dialogue offers a defaults for
each parameter. A default study name
of form “Siten” is provided in the
parameters dialogue, where “n” is a
number chosen by the program
according to what names are currently
used in the sms\studies subdirectory.
         Latitude and longitude are the
geographic coordinates in decimal
degrees (DD) at the point clicked on the
View display. The values can be
changed in the dialogue box and will be
accurately represented through all
subsequent calculations and display of
results.                                    Figure 8 - Modeling Parameters Input

2
  J.J. Egli, “Radio Propagation Above 40 MC Over Irregular Terrain”, Proc. IRE, vol. 45, pp 1383-1391, October
1957. Attached here as Appendix A.
3
  Ibid, Fig. 4, p. 1386. The Revised Egli Model still incorporates a “factor 1” (0 dB) correction for 50% location
variability, though the model is no longer purely statistical. The user is advised to consider the referenced table if
other variability factors are sought. For example, Egli suggests using a 20 dB field strength margin beyond the
calculated 50% value for 99% location reliability at 150 MHz.
                                                                                                                     6
        The loss contour (151 dB) is that which would depict a receive threshold of -137 dBW (1
µV into 50Ω) coverage from a 25 watt transmitter with a unity gain antenna and no other TX/RX
gains. [See the subsequent section, “Contour Selection” for further details.] Up to 8 values
between 0 and 200 dB can be provided, separated by spaces, commas, or tabs.
        The default transmit frequency was chosen to match a common band used by the client.
Sub-megahertz values are not necessary for accurate modeling. The Egli Model was originally
designed for frequencies between 40 and 1000 MHz; any value in that range can be input.
        The center of radiation is typical provided as the height above ground level (AGL) in
meters at the center of the antenna radiating element.
        Gain coupling is a subject discussed more fully in the section, “Contour Selection”. If
antenna system gains are to be included in loss calculations (as opposed to being manually
considered when a contour is selected), they must be included here. All transmit and receive
system gain elements - antennas, feedlines, duplexers, etc. - are included in their respective input
boxes.
        If a directional antenna pattern is to be employed, it can only be done with gain coupling
and a supplied antenna file name. A default of ‘OMNI’ is offered for omnidirectional gain
coupling, where all system gains are applied as indicated. Any other antenna name will prompt
the modeling engine to search the sms\permdata\antennas subdirectory for a file of that name
which describes the pattern. If none is found, an omnidirectional pattern is employed.
        TX and RX antenna system gains are only applied when gain-coupling is used. Included
are the sums of all system factors the user wishes to take into account along the signal path. This
may include feedline, connector, and cavity losses (negative gains) as well as antenna and pre-
amplifier gains. When using a directional antenna, include only non-antenna factors in the TX
system gain input box. Values between -25 and 25 dB are considered valid.


                                           Omnidirectional                Directional
                                             Antenna                       Antenna
    Gain Coupled
       Antenna File Name                    OMNI [default]         From sms\permdata\antennas
       TX Antenna System Gain                     Π                  Only non-antenna gains
       RX Antenna System Gain                     Π                            Π
       Downtilt
                                                  Π                            Π
       Vertical Beam Width
                                                  Π                            Π
       Directional Antenna Azimuth
                                                  -                            Π
    Non-Gain Coupled
      Antenna File Name                           -                            -
      TX Antenna System Gain                      -                            -
      RX Antenna System Gain                      -                            -
      Downtilt                                    Π                            Π
      Vertical Beam Width                         Π                            Π
      Directional Antenna Azimuth                 -                            -

                      Table 1 - Antenna and Gain Factor Applicability

       Downtilt, vertical beam width, and directional antenna azimuth are all provided in
degrees. Downtilt and beam width apply omnidirectionally in any modeling run. The antenna
                                                                                                  7
azimuth is only employed with gain-coupled directional antennas and is otherwise ignored. The
SMS Revised Egli Model does not use vertical antenna patterns, per se, but does add 3 dB of path
loss to locations outside the antenna’s vertical beam. Within 500 meters of the transmitter,
locations outside the vertical beam are essentially ignored to prevent skewing of contours.
         The model extracts terrain profiles and calculates propagation on a variable number of
radials away from the transmit site. The number of radials is left up to the user, though 360 (1
degree separation) is offered as standard. Modeling speed is directly related to the number of
radials, their length, and distance between samples, so these factors can be varied to shorten
times.
         The length of radials should be chosen so that the contour(s) of interest will not extend
beyond their end. This is an educated guess by the user; error on the conservative side by
choosing long radials. If the radial length is underestimated, the contour will artificially show as
being right at the end. This artifact is necessary to preserve the integrity of the coverage polygon
and is usually apparent upon initial inspection. Radials lengths of up to 200,000 meters can be
used, though the minimum necessary is optimal.
         Similarly, sample distance in meters is optimally chosen to match that of the underlying
terrain database: 3” or 75-90 meters, depending on latitude. Greater sample resolution provides
little additional accuracy because the nearest, original USGS DEM value is chosen for each point
along the radials.
         The earth curvature factor is generally accepted as 1.3333 (4/3rds), but has here been
calculated more accurately for the client’s location.


                                                   Range and Units                     Default
          Study Name                            128 characters, no extension             ‘Siten’
          Latitude                               -90 < decimal degrees < 90                  -
          Longitude                            -180 < decimal degrees < 180                  -
          Loss Contours                                  0 < dB < 200                      151
          Transmit Frequency                          40 ≤ MHz ≤ 1000                      155
          Center of Radiation AGL                    0 < meters ≤ 1000                      10
          Gain Coupling                                 ‘YES’ or ‘NO’                     ‘NO’
          Antenna File Name                    From sms\permdata\antennas               ‘OMNI’
          TX Antenna System Gain                      -25 ≤ dB(d)4 ≤ 25                      0
          RX Antenna System Gain                       -25 ≤ dB(d) ≤ 25                      0
          Downtilt                                   -90 < degrees < 90                      0
          Vertical Beam Width                          0 < degrees < 90                     18
          Directional Antenna Azimuth                 0 ≤ degrees < 360                      0
          Number of Radials                              0 < n < 65536                     360
          Length of Radials                       1000 ≤ meters ≤ 200,000               160,000
          Sample Distance                            0 < meters ≤ 1000                      90
          Earth Curvature Factor                           1≤K≤2                           1.24

                              Table 2 - Propagation Parameters Details



4
  Ibid, p. 1384. The Egli Model is built upon plane earth power loss between dipoles, therefore antenna gain
figures should be referenced in dBd.
                                                                                                               8
Catalyst File
        Information entered through the modeling parameters input dialogue passes into the
catalyst file, a simple text file containing all parameters used by the modeling engine and serving
to document them for future reference. It is generated automatically from ArcView with
comments describing its contents as shown in the sample below, taken from sms\tools\catalyst.txt.
The catalyst file is saved in the form of “study_name.txt”, or “site1.txt” for the example shown in
Figure 8.
        Catalyst files can be created outside of ArcView for use in the command line version of
the modeling engine as described under “Command Line Execution” below. The ‘Propagation
Study Management’ section above describes dialogues available from the main ArcView SMS
menu for catalyst file management.
 / Demonstration Propagation Information File
 /
 / This file is usually generated automatically.
 /
 / Any line beginning with a '/' is considered a comment. Each propagation
 / parameter must be provided, even if it will be ignored, and must be in
 / the correct sequence.
 /
 / Study Name - Use valid file name
         demo
 / Site Latitude - decimal degrees
         46.50
 / Site Longitude - decimal degrees w/sign
         -112.01
 / Distance Between Samples - 0<meters<=1000
         90
 / Radius from Transmitter - 1k<=meters<=200k
         160000
 / Gain-Coupling - 'YES' or 'NO' to indicate coupling of antenna gain
         NO
 / Loss Contours to Produce - 0<dB<200 (up to 8 separated by spaces, commas, or tabs)
         162,156,150
 / Path to Terrain Data - e.g. c:\win32app\mt-gsi (no terminating '\')
         c:\win32app\mt-gsi
 / Path to Antenna Files - e.g. c:\win32app\sms\permadata\antennas (no terminating '\')
         c:\win32app\sms\permdata\antennas
 / Path for Intermediate Output Files - e.g. c:\win32app\sms\temp (no terminating '\')
         c:\win32app\sms\temp
 / Path for Final ArcView Output Files - e.g. c:\win32app\sms\studies (no terminating '\')
         c:\win32app\sms\studies
 / Antenna File Name - use 'OMNI' for omnidirectional or no gain-coupling
         OMNI
 / Antenna Center of Radiation Above Ground Level - 0<meters<=1000
         10
 / Antenna Downtilt - -90<degrees<90
         0
 / Antenna Vertical Beam Width - 0<degrees<90
         18
 / Directional Antenna Azimuth - 0<=degrees<360
         0
 / Transmit Antenna System Gain - -25<=dBd<=25 (ignored if not gain-coupled)
         5.25
 / Receive Antenna System Gain - -25<=dBd<=25 (ignored if not gain-coupled)
         0
 / Earth Curvature Factor (K) - 1<=K<=2 (typically 4/3)
         1.24
 / Transmit Frequency - 40<=MHz<=1000 (Egli)
         155.000
 / Number of Radials from Transmitter - 0<radials<65536 (though not recommended)
         360


 - Sample Catalyst File -

                                                                                                 9
Contour Selection
        The shapefile created by a modeling run contains one or more polygons representing the
geographic area within which propagation losses are less than the threshold values input as loss
contours. In practice, the outer boundaries of these polygons are depicted on maps, thus
appearing as contours. The original, Arc/Info-based SMS modeled propagation in terms of losses
rather than received power or field strength; this has been carried on in the ArcView version.
        Some system engineering typically takes place before a model is run. A decision is made
whether a directional antenna will be used, what the transmitter power output is, and what receive
power or field strength level is of interest. Given these parameters and TX/RX system gains, a
loss contour of interest is arrived at.


 Example:

              We’re interested in the practical VHF-high band coverage from a site for mobile
     receivers. Considering a received power level of -137 dBW (-107 dBm or 1 µV into 50Ω) as the
     margin of coverage, transmitter power and TX/RX system gains are factored for selection of an
     appropriate loss contour.
              If a 100 watt transmitter is feeding a 5.25 dBd gain base antenna through 1.25 dB of
     feedline and cavity losses to a 3 dBd gain mobile antenna, the factors would be:

                  PRX = PTX + GTX + GRX - LP, where LP = Propagation Loss

                            -137 dBW = 20 dBW + (5.25-1.25) + 3 - LP

                                               LP = 164 dB

             The loss contour of interest is 164 dB.


        Omnidirectional models are easiest to calculate, display, and adapt because all losses and
gains apply equally in all directions. The system engineer can assess different TX/RX system
configurations without having to re-run the model by simply choosing an appropriate contour to
represent the change. For instance in the example above, the 158 dB contour would depict the
same coverage level if a receive antenna of -3 dBd gain (6 dB difference) was substituted.


Gain Coupling
        The SMS propagation model provides gain-coupling of transmit and receive antenna
systems to loss figures when necessary. Gain-coupling causes antenna and system gains (or
losses) to be included in actual loss calculations and contour depictions. The use of directional
antennas in modeling requires gain-coupling because, by definition, transmitter gains aren’t
applied equally in all directions.
        Transmit and receive gains exclusive of the TX antenna do still apply omnidirectionally
and the careful system engineer can adapt models for varying TX/RX gain factors without
rerunning. By using the “Set Propagation Parameters” dialogue from the main SMS menu, the
user can create new contour sets and shapefiles very quickly without rerunning the model. This is
                                                                                                  10
a valid approach for assessing omnidirectional power and gain changes. For example, there is no
need to rerun a model to assess what effect doubling transmit power would bring; simply generate
a new contour 3 dB greater than the current one.
        The option to skip gain-coupling was included in the original SMS because it was more
efficient to apply global factors (such as omnidirectional and system gains) outside of the loss
calculations in selection of coverage contours. When gain-coupling is selected for any model but
one using a directional antenna, the same gain figure is being added to hundreds of thousands of
loss calculations. Once the engineer becomes comfortable with selecting appropriate coverage
contours for omnidirectional models, gain-coupling will probably be used only when necessary.


Antenna Files
        The Spectrum Management System uses simple text files to describe directional antenna
patterns. An example is distributed as sms\permdata\antennas\sample.dat. Figure 9 below
shows the initial portion of this file.
        Any line in the antenna data file beginning with a slash (“/”) is ignored. All other lines are
evaluated as numeric input, one value per line. The first line is considered the gain at the center of
the main lobe. All subsequent lines are considered azimuthal gains relative to the main lobe, each
equally spaced from the next in a full, clockwise 360° pattern. The number of azimuths can vary;
the spacing in degrees between azimuths is calculated from the number of valid input lines.

                / Andrew atw-c3.dat
                /
                / Main Lobe Gain (dBd)
                2.00
                /
                / Azimuthal Gain Relative to Main Lobe (dB)
                / First value is the center of the main lobe (0 degrees)
                / Last value is 360 degrees - azimuth_increment
                / (e.g. 359 where azimuth increment is 1 degree
                0.000
                -0.009
                -0.017
                -0.026
                -0.044
                -0.061
                -0.087
                -0.114
                .
                .
                [continued]

               Figure 9 - Sample Antenna Data File


        Any discrepancy in the antenna data file found by the propagation modeling engine causes
reversion to an omnidirectional, non-gain coupled model.




                                                                                                   11
Command Line Execution
       A command line version of the modeling engine is included as sms\bin\smsprop.exe. It
provides the capability for batch jobs where interactive use is not desirable. Usage and parameter
information is displayed by entering ‘smsprop’ with no arguments, as show in Figure 10.




Figure 10 - Command Line Usage

       The catalyst file has to be in the current directory or its path provided on the command
line. Terrain data, antenna, intermediate output, and ArcView output file paths used by the
engine are provided within it. Though the catalyst file is automatically named within ArcView to
match the chosen study name, that need not be so when using smsprop from the command line.
All output file names are based on the study name provided inside the catalyst file.


APCO Database Integration

         Since the ISD-SMS has been extensively customized for an APCO frequency advisor, it
was desirable to incorporate means for licensed transmitter site information to be accessible within
ArcView. The SMS main menu provides access to an Avenue script that imports dBase III-
format database extracts from the APCO frequency coordination system. This two-stage process
begins outside of ArcView by the user running a FoxPro program against the APCO database.
The resultant .dbf file contains a join of its frequency and callsign tables. Latitude, longitude,
callsign, frequency, and several other attribute fields are taken from the tables. This extracted
data is immediately readable by ArcView as a table, but requires further processing by the Avenue
script to create a site shapefile.


                                                                                                 12
Procedure
         On the computer running APCO’s coordination system, run extract.bat as provided by
GSI. This batch file initiates FoxPro with a program file that runs an SQL extract of data,
compresses the results, and saves it to diskette as apcodata.zip.
         The compressed files are transferred to the SMS machine on diskette where the user
selects ‘Refresh Site Data’ from the main SMS menu under ArcView. The dialogue below is
displayed.
         Upon selection
of the compressed
APCO site data, the
script decompresses the
file, loads the dBase-
format file as a table,
and makes a shapefile
of its sites. Any
existing themes that are
flagged as APCO site
data (as installed by this
process) are updated
and their sources over-
written.                    Figure 11 - APCO Site Data Refresh
         Note that the
paths for FoxPro, the APCO database files, and PKZIP are fixed in the batch file and FoxPro
program file; this extraction process is installation-specific. The SMS machine must have
PKUNZIP in its executable program path. A DOS shell is spawned from ArcView to decompress
apcodata.zip; no path is provided to PKUNZIP.


Programming Notes

          A “project dictionary” is used to organize and manage the array of objects created under
the Spectrum Management System. Configuration and other vital information is stored here for
accessibility anywhere within ArcView. This Avenue programming technique helps prevent
proliferation of objects that can occur within projects.
          Use the ‘Show Project Dictionary’ of the SMS main menu to see objects stored in the
dictionary and their values. The majority of items are paths used for various aspects of the
system. These paths are set by the Avenue script utl_buildprjdict that runs when an SMS project
is first loaded.
          Avenue scripts included with the SMS are formatted and documented following ESRI’s
recommendations. Extra effort has been made to make the scripts self-explanatory to users with
some programming background and familiarity with Avenue. An empty template script
(_template) has been provided for user expansion of the SMS.




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     Appendices




14
Appendix A

Radio Propagation Above 40 MC Over Irregular Terrain - The Egli Model
Appendix B

NTIA Definitions and Relationships of Telecommunication System Terms




                                                                       16
Appendix C

Softwright TAP Tips: Calculating Talk-Out and Talk-Back

Mobile Radio Technology: Field Intensity Formulas and Their Use