NBS Special

Publication

480-19

A111D3 OTISQS

NAn INST OF STANDARDS & TECH R.I.C.

A1 11 03091 505

Urban Sciences, Inc/Dlgltal data transmi QC100 .U57 NO.480-, 19, 1977 C.1 NBS-PUB

Digital Data

Tests on

Voice Channels

Law Enforcement

Equipment

Technology

U.S. DEPARTMENT OF

COMMERCE

National Bureau of

Standards

/ W \

'If

'180-19

17
ACKNOWLEDGMENTS

This report was prepared by the Law Enforcement Standards

Laboratory of the National Bureau of Standards under the

direction of Marshall J. Treado, Program Manager for Communications Systems, and Jacob J. Diamond, Chief of LESL.

The principal investigator on this project was John Furze of Urban

Sciences, Inc. The assistance and cooperation of the personnel of

Allegheny County, Pennsylvania, is deeply appreciated.
Data

Tests on

Voice Channels

by

Urban Sciences, Inc.

1 77 Worcester Street

Wellesley, Mass. 02181

prepared by

Law Enforcement Standards Laboratory

Center for Consumer Product Technology

National Bureau of Standards

Washington, D C. 20234

prepared for National Institute of Law

Enforcement and Criminal Justice

Law Enforcement Assistance Administration

U.S. Department of Justice

Washington, D. C. 20531

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

, NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director
Library of Congress Catalog Number: 77-6 00023 National Bureau of Standards

Special Publication 480-19

Nat. Bur. Stand. (U.S.), Spec. Publ. 480-19, 63 pages CODEN:XNBSAV

\

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For sale by the Superintendent of Documents,

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(Order by SD Catalog No. 013.10:480-19). Stock No. 003-01773-6 Price $2.10

(Add 25 percent additional for other than U.S. mailing).
FOREWORD

The Law Enforcement Standards Laboratory (LESL) of the National Bureau of Standards (NBS) furnishes technical support to the National Institute of Law

Enforcement and Criminal Justice (NILECJ) program to strengthen law enforcement and

criminal justice in the United States. LESL's function is to conduct research that will assist law enforcement and criminal justice agencies in the selection and procurement of quality equipment.

LESL is: (1) Subjecting existing equipment to laboratory testing and evaluation

and (2) conducting research leading to the development of several series of documents,

including national voluntary equipment standards, user guidelines, state-of-the-art surveys, and other reports.

This document is a law enforcement equipment report developed by LESL under

the sponsorship of NILECJ. Additional reports as well as other documents are being

issued under the LESL program in the areas of protective equipment, communications

equipment, security systems, weapons, emergency equipment, investigative aids,

vehicles, and clothing.

Technical comments and suggestions concerning the subject matter of this report

are invited from all interested parties. Comments should be addressed to the Law

Enforcement Standards Laboratory, National Bureau of Standards, Washington, D.C.

20234.

Jacob J. Diamond, Chief

Law Enforcement Standards

Laboratory

iii

CONTENTS

Page

Foreword iii 1. Introduction 1

2. General Discussion of the Tests 2

2.1. General 2

2.2. Description of Base Site and Test Routes 2

2.3. Description of Radio Equipment 7

2.4. Description of Data Equipment 7

3. Test Procedure 11

3.1. General 11

3.2. Preliminary Tests 11

3.3. Modem—Radio Interface 12

3.4. Frequency Response Tests 13

3.5. Data Transmission Tests 14

4. Mobile Digital Data Transmission 15

4.1. General 15

4.2. Bandwidth Limitations 16

4.3. Power Limited Errors 18

4.3.1. General 18

4.3.2. Overall Signal-to-Noise Effects 18

4.3.3. Fading and Impulse Noise 19

4.3.4. Time of Day Variations 19

5. Test Results 19

5.1. Measured Error Rates 19

5.2. Comparison of Theoretical and Empirical Results 21

6. Conclusions 22

Appendix A. References 23

Appendix B. Frequency Response Measurements 25

Appendix C. Test Results 29

LIST OF TABLES

Page

Table 1. Downtown route locations 2

Table 2. North suburban route locations 4

Table 3. South suburban route locations 4

Table 4. VHF data tests 15

Table 5. UHF data tests 15

Table 6. Comparison of theoretical and measured results 21

V

DIGITAL DATA TRANSMISSION TESTS

ON VOICE CHANNELS

To study the transmission and reception of digital data over typical voice channels, a series of tests was performed in Allegheny County, Pennsylvania, using existing local government

transmitting sites and a specially equipped mobile unit. Carrier frequency, digital data transmission rate, modulation technique, range of transmission, speed of the mobile unit, and

time of day were varied. The tests were conducted in both urban and suburban environments. Key words: Data transmission tests; digital data transmission; mobile digital transmission equipment; voice channels for digital transmission.

1. INTRODUCTION

This report presents the details of tests of digital data transmission over typical

voice grade FM mobile radio channels. The main objective of the tests was a determination of certain aspects of digital data propagation in the FM mobile radio

environment. These tests were conducted in Allegheny County, Pennsylvania, during

the period November 1973-January 1974.

Of significant importance to the operation of law enforcement digital

communication equipment is the requirement that it interface with existing pohce radio

networks. These networks provide the existing voice communications for police

operations and will also provide the media for almost all future communications. The

frequencies which compose these networks are selected from both the VHF and UHF

bands allocated for law enforcement land-mobile usage. Each of these frequency bands

have different propagation characteristics which affect digital data transmission in different ways. As a result of a prior study [8]' it was found that the data rates which

are used to transmit information digitally vary from about 300 to 3000 bits/second

depending on the type of channel involved and the capability of the equipment being

offered.

It was mainly because of these two variables that tests were undertaken to measure the message error rate at these two frequency bands and at various data rates. Other parameters which were varied during the tests were modulation technique, speed

of vehicle, distance of vehicle from base station, and time of day. The amplitude and

envelope delay vs. audio frequency responses of the two radio systems used in the tests were also measured. Test results are included in this report as appendices.

In addition, a general description of the tests is included along with a discussion of the location of the transmitting sites and the routes used during the tests. Characteristics of the FM radio equipment are also discussed along with the data

modems and the data generating terminal equipment.

The section on test procedures includes those used in the alignment and

adjustment of operating levels of the radio equipment. The detailed interface parameters

between the modems and the radios are also described. Test methods for the frequency

response and the digital data tests may also be found in this section.

The section on test results includes a comparison of the various data and a discussion of the effects of impulse noise, fading, and the speed of the test vehicle and

carrier frequencies with respect to errors in the data. A comparison between the

theoretical calculations and the empirical data with respect to probability of bit error is also provided.

Vicurei in brackela indicate the literature referencea at the end of ihia paper.

1
2. GENERAL DISCUSSION OF THE TESTS

2.1. General

The testing consisted primarily of transmitting a known digital data message of fixed block length from a base site to a test vehicle. The test vehicle received and

decoded the data and compared the received data with a replica of the transmitted data,

thereby determining the error rate. The test vehicle was driven on predetermined routes and a test pattern transmission was initiated from the base location when the vehicle was at the selected test points.

Co-located VHF and UHF transmitters were used for the tests. The VHF

transmitting frequency was 39.02 MHz, and is presently operational as the dispatching

channel for the County of Allegheny Police. The UHF frequency used was licensed to the County Health Department at 453.8 MHz. Both transmitting sites were located on

top of a knoll overlooking the city of Pittsburgh.

A number of parameters were varied during the tests in addition to the carrier

frequency of operation (i.e., 39 vs. 454 MHz). The tests were performed with two

modulation techniques, noncoherent frequency shift keying (FSK) and noncoherent

phase shift keying (PSK), i.e., DPSK. Three d^ta rates were investigated with FSK and

two with DPSK, with one common data rate. The reasons for the selection of the data

rates are discussed in paragraph 3.5. Vehicle speed was varied from 0-45 miles per hour

at distances up to 10 miles.

2.2. Description of Base Site and Test Routes

The base transmitting site was located at the La Grande Apartments at Grandview

Avenue and Sweetbriar Street in the Duquesne Heights area of Pittsburgh,

Pennsylvania. This site is southwest of the downtown Pittsburgh area, and the

apartment building consists of eight floors and is at a natural elevation of 1180 feet,

giving an antenna height of approximately 1250 feet. The terrain of the greater

Pittsburgh area becomes evident when it is observed that there is more than a 400-foot

drop from the antenna site to the Ohio River in approximately two-tenths of a mile.

Three routes were selected for the mobile data tests; a downtown route, a north

suburban route, and a south suburban route. The locations of the base transmitting site and the downtown route are shown in figure 1. There are 10 test points in the downtown

route, as designated on the map. These test points are also listed in table 1. The north

suburban and south suburban routes are shown in figure 2. Both routes consist of over 20 test points, as indicated on the map and in the lists of locations in tables 2 and 3.

Table 1. Downtown route locations

Location Description

1 Strawberry Way & Grant

2 Grant & Oliver 3 Grant & 4th 4 Blvd. of Allies & Smith Field 5 Blvd. of Allies & Market St. 6 Stanwix & 3rd

7 Stanwix & Market St. 8 Liberty & Market St. 9 7th & Garrison

10 7th & William Penn

2
Figure 1. Downtown route.

In addition to the maps of the test areas, photographs of the area surrounding the

test site were taken and are included to show the terrain; all were taken from the roof of the apartment building. The first photograph, figure 3, was taken looking east toward

the downtown Pittsburgh area. Figures 4 and 5 are both of the north suburban route. The former is a photograph of the first leg of the route traveling northwest edong the

Ohio River, while the latter is of the return leg down the AUegheny River. Figure 6 was

taken looking due south, the cross-country leg of the south suburban route being behind

the first group of hiUs.

3
Table 2. North suburban route locations

Location Uescnption

1 Saw MiU Run & Rte 60

2 Ohio River Blvd. & Marshall Ave. 3 Ohio River Blvd. & McKees Rocks Brdg. 4 Ohio River Blvd. & Bellevue

5 Ohio River Blvd. & Fisk 6 Ohio River Blvd. & Creenbelt

7 Greenbelt & Crawford

8 Creenbelt & Lawries Run

9 Creenbelt & Heis Run

10 Creenbelt & Rte 19

11 Greenbelt & McKnight

12 Creenbelt & Duncan

13 Creenbelt & Hubbard

14 Creenbelt & Rte 8

15 Rte 8 & EUin wad

16 Rte 8 & Spencer

17 Rte 8 & Saxonburg

18 Rte 8 & Etna

19 Rte 8 & Parker

20 Rte 8 & Hoffman

21 Rte 8 & Herrs Island 22 Rte 8 & Heinz

23 9th St. & Railroad Brdg.

Table 3. South suburban route locations

Location Description

1 Merimao St. 2 South 51 & Liberty Tubes

3 Rte 51 & Edgebrook

4 Rte 51 & Rte 88

5 Rte 51 & Brownsville Rd.

6 Rte 51 & Whitehall Boro Bldg.

7 Rte 51 & Curry HoUow Rd.

8 Curry Hollow & Brownsville 9 Broughton & E. Park

10 Broughton & Library

11 Connor & Oregon Trail 12 Washington & Mt. Lebanon Blvd. 13 Rte 19 & Washington

14 Rte 19 & Beverly

15 Rte 121 & Creentree

16 Main St., Carnegie

17 Entrance to Rte 79

18 Rte 279 & Chartiers 19 Rte 279 & Carnegie Exit 20 Rte 279 prior to Creentree

21 Rte 279 after Creentree

22 Rte 279 & Rte 51

4
5
Figure 3. View looking east from transmitter site.

Figure 5. View looking northeast from transmitter site

6
Figure 6. View looking south from transmitter site

2.3. Description of Radio Equipment

Both the county police VHF system and the county health UHF system base

station and mobile transceivers were of the same manufacture. They were hybrid

equipment, primarily solid-state with a tube-type power amplifier.

The VHF base transmitter was floor mounted and rated at 330 watts of rf output

power. It was connected to the rooftop antenna by 100 feet of 50 ohm aluminumsheathed foam-filled cable. The antenna was a monopole antenna with gain equal to a half-wave dipole. The mobile transceiver used was rated at 100 watts of output power

with a 12 dB SINAD sensitivity level of 0.25 /xV. The 0 dB omnidirectional gain mobile

antenna was mounted on the trunk.

The UHF base transmitter was also a floor mount installation located in the same

room as the VHF base station. It was rated at 250 watts of output power. The antenna

system consisted of a colinear array with 10 dB omnidirectional gain and was coupled to the base transceiver with 100 feet of 50 ohm corrugated copper foam-filled cable. The

output power of the mobile transceiver was 75 watts and it had a 12 dB SINAD

sensitivity level of 0.35 /u,V. The mobile trunk mount antenna had an omnidirectional

gain of 5 dB. The base antennas are shown in figure 7 (camera looking northeast), while

the mobile antennas are pictured in figure 8.

2.4. Description of Data Equipment

The base station data generating equipment was required to form a known bit pattern at baseband, convert the bit pattern into an analog signal by either of the two

desired modulation techniques, transmit the data at each required transmission rate, and provide an analog signal compatible in level and frequency content with the radio

equipment. The mobile data receiving equipment was required to decode the data at all transmission rates and accept the analog signal for decoding from a suitable output at the radio receiver, convert the analog signal into baseband data at each modulation

technique, and determine the bit error rate. The terminal equipment and modems, which were leased, consisted of two TLA3000 Telephone Line Analyzers, two 1800B Data Modems and two 2400B-1 Data

Modems.

One TLA-3000 served as the source of the baseband data, a 511-bit pseudo-random

pattern normally used for checking error rates on telephone lines. The second telephone

line analyzer served as a receiver of the baseband data in the test vehicle. The mobile

telephone line analyzer also made a comparison between the received data and the

known transmitted pattern (stored in memory) in order to determine the bit error rate

7

Both of the TLA-3000 terminal units were interfaced with the modems by means of standard connectors [2]. The 1800B data modem was an asynchronous FSK modem with an externally

clocked variable data rate from 300 to 1800 bits per second. The analog transmit output

provided the FSK information at 0 dBm at 600 CI. The receiver of the modem was

capable of decoding any compatible FSK signal within a dynamic range of 0 to -50

dBm.

The 2400B-1 modem employed a synchronous (internally clocked) DPSK

modulation scheme. It operated at two data rates, 1200 and 2400 bits per second. Since

it was a four-phase modem, this signaling rate was equivalent to 600 and 1200 baud. The

analog transmit output and the received dynamic range were similar to the 1800B.

Both the TLA-3000's provided the necessary functions to determine the amplitude

and envelope delay vs. audio frequency response of the FM radio system. The details of these tests are given in paragraph 3.4. Because of equipment voltage requirements, a

dc-to-ac converter (inverter) was used to provide the 120 Vac, 60 Hz power in the test vehicle.

The receive analyzer and modem and the transmit analyzer and modem are shown

in their test positions in figures 9 and 10. Basic block diagrams of the transmit and

receive configurations are shown in figures 11 and 12.

Figure 9. Receive analyzer and modem in vehicle

9
Figure 10. Transmit analyzer and DPSK modem at base station

TELEPHONE

LINE ANALYZER

MODEM

'600 a ,0 dBm

TRANSFORMER SWITCH

UHF

MICROPHONE INPUT VHF

•USED FOR AMPLITUDE AND ENVELOPE DELAY RESPONSE TESTS

Figure 11. Data transmit configuration .

10
l2Vdc- INVERTER

UHF

120 Vac

HIGH SIDE

VOLUME CONTROL

VHF

SWITCH TRANSFORMER

600

•A

120 Vac

MODEM

TELEPHONE

LINE

ANALYZER

600

•LEVEL AT POINT A TO BE WITHIN DYNAMIC RANGE OF RECEIVE MODEM.

USED FOR AMPLITUDE AND ENVELOPE DELAY RESPONSE.

Figure 12. Data receive configuration

3. TEST PROCEDURE

3.1. General

The initial tests were performed on the mobile transceivers that were used to receive the data in the test vehicle. The radio manufacturer's adjustment and alignment

procedure for the mobile receiver was followed. Both base transmitters had had

preventive maintenance servicing within 3 months of the tests so they were not adjusted

or aligned solely for the data tests. Tests were performed to determine the modulation

index and signed levels needed to provide good data transmission quality. The effective

radiated power of both transmitters was obtained (see par. 3.2). In order to provide the proper interface between the modem and the transmitter

and receiver, pads and transformers were selected so that the proper input/output levels would be achieved. The signal generator/power meter mode of the telephone line analyzer was very helpful in determining these values.

Test procedures were developed for the measurement of the amplitude and

envelope delay response of each of the radio systems. The information recorded from

these two tests was used for characterizing the channel with respect to bandwidth

limitations. The frequency response information was also used to determine the

equaUzer settings on the modems.

3.2. Preliminary Tests

Initial tests were performed on both the VHF and UHF mobUe receivers using

procedures recommended by the manufacturer. The receiver edignment included

discriminator and oscillator checks, rf ampUfier and selectivity adjustments, and a rf frequency adjustment. The audio power output and distortion, usable sensitivity, and

the modulation acceptance bandwidth were also measured and were found to be within

acceptable limits.

11
The base station transmitters had received a service check 3 months prior to their use in the data tests so the transmitter alignment procedures were not instituted. The

service check had indicated that both transmitters were within manufacturer's

specifications. As the power output of the final power amplifier is a frequently adjusted

variable, measurements of the incident and reflected power of both systems were made.

The results of the measurements indicated that the effective power reaching the antenna

terminals, accounting for all mismatches and line losses, was 100 watts in the VHF

mode and 150 watts in UHF. The gain of the VHF monopole was approximately 2 dB,

while the gain of the UHF colinear array was approximately 10 dB, above an isotropic

radiator. Taking the antenna gains into account, the effective radiated power of each

system, referenced to! an isotropic radiator, becomes 160 watts for VHF and 1500 watts

for UHF.

3.3. Modem—Radio Interface

The transmit and receive modem—FM radio interface required the use of

impedance matching transformers and resistive attenuators in order to provide the

proper signal levels for data transmission. However, the first step in the interface

problem was the determination of the proper signal level at the transmit microphone

input in order to produce a reasonable modulation index.

The 2400B-1 DPSK modem uses a carrier frequency of 1800 Hz while the mean of the two frequencies used in the 1800B FSK modem is 1700 Hz. The audio power output

of both modems is 0 dBm. A variable level test tone at 1750 Hz was chosen because it was a tone central to the power spectra of all the data of both modems.' A

communications monitor was used to receive and display the test tone on a calibrated

scale. With the deviation displayed, the signal level at the microphone input of the

transmitter was increased untU distortion of the received test tone was observed on the

display. The distortion occurred at a deviation of ±2.8 kHz for both the VHF and UHF

radio systems. The input signal level required to produce the highest distortionless

deviation was read from the telephone line analyzer and recorded. Knowing this required input level and the standard output of the modems (0 dBm), an impedancematching transformer and resistive attenuator were chosen.

The transmit connection to the modems (600 fi balanced, 0 dBm) fed a 600 ft balanced "H" attenuator which provided 40 dB of loss. A 500 ft to 50 Kft audio

transformer provided the impedance match to the microphone input. The microphone

input was bridged by the data transmit line in order to retain the capability to provide

voice communication to the mobile and manual transmitter keying for data transmission.

The receiver interface was made to the high side of the audio volume control of the mobile radios. This point was chosen for two reasons: first, ease of accessibihty

(located in the front of the vehicle while the discriminator output was located in the

trunk) and second, this point was prior to de-emphasis of the recovered audio. The level requirements for this, the data receive point, were not severe since the receive modem

has a wide dynamic range. The receive data requirement was reduced to the problem of stripping the recovered audio data from the volume control without appreciably

degrading voice coverage and yet coupling at least —45 dBm of signal into the receive

modem. This was achieved by bridging the volume control with a 10 Kft to 500 ft audio

transformer. Again the transmit telephone hne analyzer was used as a test tone source

at 1750 Hz in order to deviate the transmitters. However, since the input attenuator and

matching transformer were connected to the microphone input, the output level was set

at 0 dBm to simulate the audio level of the transmit modem. The second telephone line

analyzer was used at the receiver as a power meter in order to determine whether or not

the received audio power was within acceptable limits. With the previously mentioned

audio transformer in place, the receive level at 1750 Hz was -19 dBm, well within the

12
range of the modem. These interface considerations pertained to both the VHF and

UHF base transmitters and receivers so the same interface circuitry was used for both

pieces of equipment.

3.4. Frequency Response Tests

Two independent tests of the frequency response of the VHF and the UHF radio

systems were made. In one of the tests the variation in the received audio ampUtude

with frequency was recorded while an audio signal of constant power but variable

frequency was used to modulate the transmitter. In a second test, the relative envelope

delay vs. frequency was measured. As in the amplitude response test, an audio signal of constant power and variable frequency was used to modulate the transmitter. However,

in the case of the envelope delay test, the audio test frequency was modulated to produce known sidebands, which when received, facilitated the actual measurement of the envelope delay.

The amplitude response and the envelope delay response were measured using the

two telephone line analyzers. In the case of the amplitude response measurement, the

transmit analyzer was set to a mode in which it served as a variable frequency signal

generator. The audio output of the transmit analyzer was a constant 0 dBm and the

frequency was swept manually from 300 to 3000 Hz. The receive analyzer was used as a frequency selective power meter when the amplitude response mode was selected. It provided a digital readout of the frequency and the absolute power level of the received

audio test tone within a short settling time. In performing the actual tests, the

transmitter was keyed and then the test tone was applied, resulting in the received tone

level being displayed in the mobile unit. These tests were performed at several discrete

frequencies throughout the 300 to 3000 Hz range. The relative received levels (referenced to the received level at 1750 Hz; -19 dBm) are plotted vs. frequency for both the VHF and the UHF systems in appendix B. The envelope delay measurements were made in a similar manner except for the

fact that the test tone was modulated to create sidebands. This modulated audio carrier was detected at the receive analyzer and the phase distortion introduced into the

sidebands due to the frequency sensitive envelope delay of the channel was measured

and displayed as relative envelope delay in microseconds. The telephone line analyzers were capable of making simplex envelope delay measurements through the use of a receiver synchronization technique. The initial tone transmission was made at 1800 Hz,

and after a synchronization time in which the receive analyzer oscillator circuitry was

corrected, the test was initiated. The transmit frequency was varied, searching for a minimum envelope delay reading on the receive analyzer. The frequency at which the

minimum was found was used as the reference frequency. At this point, the

synchronization process was repeated at the new reference frequency. Once the receive

analyzer display was stabilized, the correction factor was inserted into memory by

depressing a button on the receive analyzer. The transmit frequency was then varied

throughout the audio range, and the received frequency and the relative delay in microseconds were recorded at the mobile unit. These tests were performed in early

morning hours to avoid interfering with the normal dispatching procedures carried out on the radio systems. The envelope delay characteristics of the VHF and UHF radio

systems are presented in appendix B. The frequency responses of both systems were

quite similar. Therefore, their individual influences on data quality were considered

sufficiently alike to allow a valid comparison of the propagation characteristics of VHF

and UHF.

Since both amplitude and envelope delay distortion, when present to a significant

degree, are detrimental to data quality, each modem was equipped with channel

equalization. In the case of the DPSK modem, the equalization levels were strap

13
selectable to discrete levels. The level of equalization selected was the minimum

provided by the modem, that is, the equalization level for C2 conditioned, dedicated

lines. The effect of this line equalization will be discussed later. When the FSK modem

was used, the minimum or dedicated line equalization was selected by adjustment of a potentiometer.

3.5. Data Transmission Tests

In order to perform the data tests, one of the modems was inserted between the

telephone line analyzer and the radio. The interface from the modem to the radio was

identical to the interface used between the analzyers and the radios in the frequency

response tests. The interface between the telephone line analyzer and the modem was made with a cable that met the requirements of [2]. To initiate a test transmission, the transmit and receive radio systems were

selected at the base and at the mobile. Upon a voice request for data from the mobile,

the transmit sequence was initiated. The transmit sequence consisted of depressing the

push-to-talk switch on the proper microphone, muffling the microphone in a rubber pad,

and initiating the transfer of baseband data from the telephone line analyzer to the

modem by selecting a toggle switch. The baseband data was a 511-bit pseudo-random

m-sequence generated pattern.

When the data were transferred between the analyzers and the modem, the

modem began to convert the baseband bit stream into a corresponding analog pattern,

either DPSK or FSK, at the required bit rate. In the case of the asynchronous FSK

modem, the clocking signal was provided by the telephone line analyzer and provided

continuously variable data rates from 300 to 1800 bits per second. With the DPSK

modem, the clocking signal was interneJly generated and provided two fixed selectable

rates: 1200 and 2400 bits per second. When the data were received at the mobile and

coupled into the receive modem, the analog modulation was decoded into baseband data

and transferred into the receive telephone line analyzer. After a short synchronization

time, the two counters on the analyzer were zeroed. After release of the zeroing

controls, one of the counters indicated the number of bits received while the other

recorded the number of bits in error. The two modulation techniques used, binary FSK and four phase DPSK, were

selected because they corresponded to those readily available in standard modems. The

DPSK modem had a standard data rate of 2400 bits per second with an optional

selectable rate of 1200 bits per second; both rates were used. Three data rates were

used for the FSK tests: 600, 1200, and 1800 bits per second. The choice of 600 and 1200

bits per second for FSK data rates provided a direct correspondence with the 1200 and

2400 bits per second rates of the DPSK modem. This correspondence exists because the

baud rates of the two modems are identical at 600 baud and 1200 baud. The 1800 bit per

second rate for FSK was chosen to try to evaluate the bandwidth limitations of the

channel, as FSK at this rate occupies the greatest bandwidth of all the modulation

techniques. The bit block length selected for each transmission was 3000 bits. Three test routes were chosen for the error rate measurements. The downtown

route was driven 5 times at each frequency, taking 10 data points each time, switching

between VHF and UHF on alternate trips. This procedure was repeated for each

modulation scheme and data rate. Due to the high vehicular traffic density, data were

taken at most of the test points while the vehicle was stopped or traveling at approximately 15 miles per hour. A total of 500 test transmissions were made in the

downtown area. Test data, including the number of errors in each 3000-bit transmission,

are shown in appendix C.

Both the north and south suburban routes were broken into three legs: one radially

outward from the base site, one cross-country leg, and a return leg. The total length for

14
each route was approximately 25 miles, with reception locations at spacings of roughly 1 per mile. Each of the routes was driven twice. The first time a radial outgoing route was

tested, the VHF transmitter was used, switching to UHF on the cross-country route, and

reselecting VHF on the return leg. This sequence of data transmission was chosen to avoid continued use of a single channel over an extended period of time. The second

time a suburban route was tested, the procedure was reversed.

At each test point, the data were taken three times at three different vehicle

speeds. These speeds, along with the location, date, and time of test, data rate, modulation scheme, transmitter frequency, and measured errors are also given in appendix C. In order to account for time of day variations, certain portions of the

suburban routes were rechecked on different dates. A total of over 1300 test transmissions was made on the suburban routes. Tables 4 and 5 summarize the error

rates for each modulation scheme/data rate combination used in the tests.

Table 4. VHF data tests

Measured

error

Route \v

FSK DPSK

600 bps 1200 bps 1800 bps 1200 bps 2400 bps

Downtown

South Suburban

North Suburban

Both Suburban Rtes.

All Data Tests

2.0X10"^ 4.7X10^^ 6.7X10"^

1.2X10"* 8.3X10'^ 5.7X10"^

1.5X10"^ 1.5X10" 1.7X10*

6.5X10"^ 1.2X10 * 1.2X10 * 5.3X10"^ 9.8X10'^ 1.0X10'*

5.3X10'^ 5.3X10"^

1.0X10'* 1.1X10*

6.8X10"^ 9.2X10'^

8.5x10'^ 1.0X10*

7.6X10'^ 8.7X10"''

Table 5. UHF data tests

Measured

error \^ate

Route

FSK DPSK

600 bps 1200 bps 1800 bps 1200 bps 2400 bps

Downtown

South Suburban

North Suburban

Both Suburban Rtes.

All Data Tests

6.7X10"'' 6.7X10'* 2.7X10'^ 8.3X10'^ 1.4X10* 1.8X10* 3.2X10* 9.3X10* 1.3X10'^ 2.0X10* 5.5X10'* 7.7X10*

1.5X10* 4.0X10* 5.7X10*

6.7X10"* 1.3X10'^ 8.9X10"^ 1.8X10'* 5.1X10* 1.3X10'^ 3.1X10'* 7.5x10'* 2.2X10* 5.5X10'*

4. MOBILE DIGITAL DATA TRANSMISSION

4.1. General

The major purpose of the tests was to determine empirically the error rates encountered with digital data transmission over a typical FM voice-grade mobile radio

channel. Errors in data transmission are usually caused by two effects: bandwidth

limitations, which result in intersymbol interference, and low predetection signal-to-noise

ratios caused by low signal levels or high ambient noise, or both. In order to perform a

valid comparison of propagation effects on data quality between two carrier frequencies,

such as 39 MHz and 454 MHz, the bandwidth limitations and their effect on errors must

15
be taken into account. The bandwidth characteristics of both the VHF and the UHF

transmitters were measured prior to the data transmission tests. The resuUs of these

tests are presented in appendix B. The error rate performance is presented in figure 13 as a probability of bit error

vs. an average predetection signal-to-noise ratio based on statistical considerations. The

noise model used in these calculations assumed a Gaussian distribution. Because

skepticism often exists on how well calculated results compare with the actual

performance of a real system, empirical data were obtained to support these theoretical

results. A direct comparison for various points along the test routes is included in this report.

Other phenomena which affect data transmission over a radio channel are fading

and impulse noise. Fading occurs when more than one signal from the same transmitter

reaches the receiver and causes either a nulling or reinforcement of the direct-path

signal. The secondary received signals are generally reflected into the vicinity of the

receiver by nearby manmade structures. Fading phenomena are often characterized by a

specific type of multiple signal reception termed Rayleigh fading. Rayleigh fading can be

accounted for on an average basis by specifying that the values of the received signal

follow a specific distribution based on certain assumptions. Generally, all calculated

results presented are based on the assumption of slow and nonselective fading. Many

times this first-order model is not applicable due to the fact that for every Rayleigh

fading channel there are instants of time during which the signal fades to near the zero

value. If the test vehicle were located at such a nuU (highly unlikely, since a voice

request from the mobile has to be received at the base to initiate data transmission), all bits sent would have a high probability of being in error. The more likely effect would

be short bursts of errors occurring during the time when a moving test vehicle passes

through these deep fades.

Impulse noise is also of importance. This type of noise is usually generated by

phenomena such as vehicle ignition and switching transients, and can result in very high

probabilities of error. Most common instances of bit errors due to this phenomenon are due to high levels of impulse noise caused by buses or trains. Both fading signal and impulse noise phenomena occur to different degrees

depending on the carrier frequency of operation. These factors, along with the speed of the test vehicle and the data rate, cause the observed variations in the measured bit error rates. Other matters considered in this report are variations due to changes in the time

of day and the type of modulation scheme used. The time of day variations were

relatively insignificant, but the effects of the modulation techniques are evident in the

results. The relative transmission ranges of digital data and voice are also considered.

4.2. Bandwidth Limitations

In the analysis of most data channels, time dispersion effects of transmitted pulses can be attributed to the imperfect transfer characteristics or frequency response of the

channel. In the case of the telephone line, for example, the transfer function is usually

expressed in terms of attenuation and delay as a function of frequency. The envelope or group delay iUustrates the relative arrival time of various frequency components of the

transmitted signal. Attenuation distortion occurs when the relative magnitude of the

various frequency components of the original signal is varied.

The frequency components of a binary FSK waveform are not limited to the two

signaling frequencies but are spread throughout an infinite bandwidth due to the

discrete nature of the signaling process. With this in mind, infinite-bandwidth channels

might be considered necessary in order to receive a true replica of the transmitted

waveform. However, it has been shown that the amount of bandwidth required is

16
17
theoretically equal to the baud rate of the transmitted waveform. These results assume a

perfect characteristic within this bandwidth, e.g., no amplitude or envelope delay

distortion. Practical bandwidths of x hertz will not necessarily support data rates of x baud, due to intersymbol interference.

If the effects of bandwidth limitations can be eliminated, either by using low

signaling rates, transmitting over a reasonably good channel, or equalizing a poor

channel, the bulk of the observed errors can be attributed to low signal-to-noise ratios and other related effects. This is believed to be the case with the results presented in

this report.

The amphtude and envelope delay responses of both the VHF and UHF radio

systems used for the data tests are shown in appendix B. On examination of these

curves, it is evident that severe distortion of the transmitted waveforms should not occur

at the modulation rates and audio carrier frequencies used by the modems. These

curves were examined by the modem manufacturer, and the bandwidth limitations of the two channels were deemed no more severe than those encountered on C2

conditioned telephone lines. The main reason for the consultation was to ascertain the

recommended equalizer settings for the FSK and the DPSK modems. The recommended

settings were those that produced essentially no line equalization but did compensate for the distortion introduced by the modem circuitry itself. These settings resulted in a pattern of least intersymbol interference when the modems were operated back-to-back.

The transfer characteristics of the two radio channels were not considered severe enough to cause a significant amount of distortion, even at the higher data rates. However, it was found that bandwidth limitations did cause some of the errors recorded,

and they did have a tendency to cause more errors at FSK than at DPSK at the same

baud rates. This was due to the fact that FSK occupies more bandwidth due to the tone

separation. The effects of sUght differences in bandwidth limitations of the VHF and the

UHF radio systems would not be recognizable, since the characteristics of the two

systems are nearly identical, as shown in the graphs in appendix B.

4.3. Power Limited Errors

4.3.1. General

Most of the errors other than those caused by finite bandwidths are attributable to low signal-to-noise ratios. Poor signal-to-noise ratios can be due to factors such as high

path loss, high values of instantaneous noise, and deep fading. These, in combination

with other factors such as the carrier frequency of operation, time of day variations, and

the speed of the vehicle result in significant variations in decoding errors. The

interdependence of signal and noise effects, along with possible intersymbol

interference, is very difficult to isolate empirically. Generally, results are stated in terms

of gross variations or trends in the number of errors. The discussion of the error rates measured during these tests is included in section 4.4.

4.3.2. Overall SignaUto-Noise Effects The signal strength received at a mobile FM receiver depends on the attenuation

the radiated signal experiences traveling between the transmitter and the mobile. For a given effective radiated power, this loss depends on many factors, such as the frequency

of operation and the distance and terrain between the two antennas. Average expected

signal strengths at the mobile receiver can be measured or calculated through the use of proven methods and experience.

Based on average values of manmade noise and given the needed characteristics of the receiver, the expected detected noise level can be determined. When data

transmission is under consideration, this noise power is usually defined by a Gaussian

distribution of signal values. The behavior of digital data of a known modulation

18
technique, transmitted .d subsequently received at a constant signal strength

corrupted by Gaussian noise, is calculable. Such calculations are often carried out in order to compare the performance of the various modulation techniques to a first-order approximation

The average received signal and noise power at a mobile receiver vary considerably when the VHF and UHF frequency bands are compared. Differences in the

free space, flat-earth, and shadow losses encountered in radio transmission when using

these two bands are the most significant contributors to these variations. These effects are so great that in practice high gain antennas along with higher power base stations are needed to provide UHF coverage comparable to lower frequency VHF coverage.

Considerable variation in the level of manmade noise can also be expected, with the

higher noise power levels at VHF.

4.3.3. Fading and Impulse Noise

The received rf signal strength and the level of manmade noise fluctuate

considerably about their respective mean expected values. Multiple reflections from

buildings and other vehicles produce an rf standing wave pattern throughout the

coverage area. The values of the signal level in this pattern can be either higher or lower than the expected line-of-sight value due to signal reinforcement or cancellation.

The depth and width of the resultant fade patterns show definite variations with radiated

frequency due to the difference in wavelength of the signals and the reflection

coefficients of the structures. If the mobile is positioned near the minimum of a deep

fade, it is possible for the data quality to be extremely poor due to an extremely low

peak value of signal-to-noise ratio. This effect was probably insignificant because the

probability of stopping the vehicle in a very deep fade was low. The most prevalent

fading errors occurred as a moving vehicle passed through these deep fades.

Impulse noise is characterized by the fact that during certain periods of time the

noise voltage makes significant deviations from the mean. Urban manmade noise is very

impulsive and appears even more transient when a moving vehicle passes by a localized source of manmade noise.

Both multipath fades and impulse noise can cause multiple bit errors or bursts of errors depending on their time duration and severity. These error bursts can vary in size not only because of changes in the fade depth and width but also because identical

fades occupy more bit positions at higher data rates. At reasonable data rates, these

effects are probably more significant factors in the increase of errors at higher data

rates than bandwidth limitations. The size of the burst errors caused by multipath

propagation and impulse noise are influenced by the speed of the vehicle. The vehicle's

speed affects the percentage of time a fade or noise burst occupies the bit period.

4.3.4. Time of Day Variations

The multipath and manmade noise characteristics of channels vary with time of

day. The reflective surfaces which create the standing wave pattern may move or change reflection coefficient. Manmade noise phenomena vary considerably with the

time due to the daily life cycles of the populace. Some other noted variations are changes in intermodulation and co-channel interference.

5. TEST RESULTS

5.1. Measured Error Rates

The data in appendix C have been compiled into tables 4 and 5. Table 4 contains

the condensed results of the VHF tests, while table 5 presents the UHF data.

19
The UHF test results follow an expected pattern. The modulation techniques listed

in the order of increasing number of errors are: 600 bps FSK, 1200 bps DPSK, 1200 bps

FSK, 2400 bps DPSK, and 1800 bps FSK. The 600 bps FSK had the lowest error rate, as expected. The 1200 bps DPSK had a lower error rate than the 1200 bps FSK because

the longer signaling intervals associated with 1200 bps DPSK (600 baud DPSK) allowed

longer integration times through short fade and noise bursts than the 1200 baud FSK.

This effect was more than enough to compensate for the fact that errors occurred in bursts of two bits with DPSK signaling. The fact that the 1200 bps DPSK occupied less bandwidth than the 1200 bps FSK also contributed to the difference in error rate. The

signaling methods with equivalent baud rates, such as 600 bps FSK and 1200 bps

DPSK, were comparable in performance but, in general, the 1200 bps DPSK had more

errors due to the tendency for errors to occur in bursts of 2 because of the differential phase reference. Through similar arguments, the relative number of errors that occurred

at each data rate can be explained. This ordering of data was the same for both

suburban routes and the downtown route. In the case of the VHF tests, the preceding rationale is not exactly true. The

pattern followed with respect to increasing error rate for the tests was: 600 bps FSK,

1200 bps DPSK, 2400 bps DPSK, 1200 pbs FSK, and 1800 bps FSK. The relative

positions of the 2400 bps DPSK and the 1200 bps FSK are interchanged with regard to the expected results. Such a result is possible in limited testing when a relatively small

sample size is used and a very small difference in error rate is involved. This result,

along with the fact that 600 bps FSK had the highest error rate in the south suburban

tests, was probably due to external factors. When the 600 bps FSK south suburban tests and the 1200 bps FSK north suburban tests were being done, there was some evidence

of co-channel interference from another mobile unit on the same frequency. This type of interference was very detrimental to data quality in weak signal areas. However, in high

data signal strength situations, it did not hamper reception due to the FM capture

effect.For aU the data rates and modulation techniques, the downtown tests indicate

better data quality at UHF. Since the base transmitter was relatively close to the

downtown route, the bulk of the measured errors occurred in areas of high impulse

noise in combination with a deep fade. This situation is more likely to occur in the VHF

band due to the higher values of manmade noise. Most of the errors occurred in bursts

of one to four bits, with the length of the bursts tending to increase with signaling rate. The errors recorded with DPSK generally occurred in bursts of at least two bits except

in the cases when the error occurred on the last bit of the memory block. Some of the

specific instances of error occurred when the test vehicle was close to a neon sign at point 7 on the downtown route and when a bus or trolley passed nearby. However,

errors caused by bus and troUey noise were not frequent.

In most of the suburban tests, the measured error rates were lower at VHF.

Although both systems were designed to cover the same area, the VHF system provided

better signal strength at most of the test points due to the lower path and shadow loss. However, at a few test points, the UHF performance was superior to VHF. The

additional errors at VHF in these cases were caused by manmade noise. One particular

instance occurred when a passing train caused a burst of errors at VHF while testing in Carnegie.

When all the data are considered, VHF provided the lowest overall error rate at all data rates and modulation techniques. However, these tests were weighted by the fact that more data points were taken in suburban areas where the VHF coverage lyas

significantly better. In any case, consideration of these results might lead to second

thoughts about conversion to a UHF channel when the law enforcement agency is a County Police Department which spends little time patrolling urban areas.

20
In performing the tests, a qualitative estimate of the data vs. voice coverage was

made. The results indicated that they were approximately the same, although in some

instances data were rer«»' ed when no voice contact was possible. In these cases the

received data were very tughly prone to error. The variation in error rate performance due to changes in the data rates and

modulation techniques tested were not significant on an overall basis. Of course, there were isolated instances where wide variations did occur. The information throughput of the channel was not reduced at either VHF or UHF as the data rate was increased to 1800 and 2400 bits per second. Therefore, the point of severe bandwidth limitation was

not reached. Although the higher data rates achieved more information throughput, the

amount of errors also increased at the same time. In such cases, error detection and

retransmission or, even better, error correction would be needed in order to utilize the

increased throughput.

5.2. Comparison of Theoretical and Empirical Results

A path loss analysis was performed to calculate the values of signal-to-noise ratio

at three selected points along the suburban routes. These values of signal-to-noise ratio were converted into probabilities of bit error for FSK signaling with Rayleigh fading in Gaussian noise using the graph in figure 13. These two sets of values are presented in table 6 along with the average measured error rates (averaged with respect to speed) for those points at the nominal data rate of 1200 bps FSK. The three selected test sites are coded in the following manner: S15 121 & Greentree

S8 Curry & Brownsville

N13 Greenbelt & Hubbard

Table 6 also shows the "actual signal-to-noise ratio," converted from the measured

error rate through the use of figure 13. This was done so that the theoretical and actual

data could be compared as a difference in signal-to-noise ratio, shown in the last column

of the table. The agreements between the actual and calculated values are within ±10

dB.

Table 6. Comparison of theoretical and measured results

Calculated Calculated Actual Actual Location Frequency S/N ratio error rate error rate S/N ratio

VHF 40 dB 1.0X10'* 7.7X10"* 31 dB 9 dB

SIS UHF 37 dB 2.0X10"* I.IXIO"' 30 dB 7 dB

VHF 34 dB 4.0X10* 2.2X10"* 36 dB -2 dB

S8

UHF 31 dB 8.0X10"* 3.3X10"* 35 dB -4 dB

VHF 27 dB 2.0X10"^ 5.5X10"* 33 dB -6 dB

N13

UHF 22 dB 5.0X10"' 1.3X10"' 29 dB -7 dB

21
6. CONCLUSIONS

The following is a summary of the results determined from the evaluation of the

test data:

° At all data rates tested (i.e., from 600 to 2400 bps) the bulk of the bit errors were

caused by power-limited effects rather than by bandwidth limitations.

° Most of the downtown route bit errors were attributed to manmade noise effects,

which resulted in more errors with the VHF carrier frequency. The burst errors tended

to occur in groups of one to four bits.

° In general, the VHF carrier frequency provided superior data transmission

performance on the suburban routes except in the rare cases when severe manmade

noise was present.

° At UHF, the number of detected errors increased with increasing signaling rate. This was primarily due to the fact that the longer signaling intervals associated with the

lower data rates allow for longer integration times through fades and noise bursts. The

fact that the higher data rate signals occupy more bandwidth made a secondary

contribution to the ordering of the various data rates with respect to increasing errors.

° In the case of VHF, the pattern of increasing error rate with increasing data rate was not exactly reproduced. This was probably due to the fact that co-channel

interference was present at certain periods of time during the VHF tests. Co-channel

interference was found to be very detrimental to the data quality when the mobile unit was in weak signal areas. However, in high data signal strength situations, it did not hamper reception due to FM capture.

° In general, the number of errors recorded at a particular test point decreased

with increasing vehicle speed in the 10 to 40 mph range of the tests.

° The burst length of the errors was generally less than 7 bits and never more than

10 bits.

° Variation in co-channel interference was the most significant "time-of-day

variation."

° High quality data reception was generally coincident with high quality voice

reception.

" Even at the highest bandwidth occupancy (i.e., 1800 bps FSK), the bulk of the

errors was not attributable to bandwidth limitation but to the fact that the fades or impulse noise spikes occupied more bit positions at the higher data rates.

° Although the higher data rates allowed more total information throughput, the

number of errors increased to such an extent that error detection and retransmission, or

error correction, would be required in order to utilize the increased throughput at the

higher rates.

° The variations in measured error rate with changes in data rate and modulation

technique were not considered significant enough to warrant avoiding the use of high

data rates for FM radio data communication. Even though the 1800 bps FSK occupied

considerable bandwidth, the limitations of the channel were not reached. The

information throughput was stiU increasing at the higher data rates. At 600 bps FSK, 89

percent of the messages were received without error, while at 1800 bps FSK, 81 percent were received error free. Therefore, the throughput was 2.7 times higher at 1800 bps.

° The theoretical and empirical signal-to-noise ratios agreed within ±10 dB.

22
APPENDIX A

References

[1] Bruchert, E. J., and Sangster, J. H., The Effects of Fading and Impulse Noise on

Digital Transmission Over A Land Mobile Radio Channel , (Decemher 1969).

[2] EIA Standard RS-232-C, Interface Between Data Terminal Equipment and Data

Communications Equipment Employing Serial Binary Interchange , (August 1969).

[3] Kelly, T. C, and Ward, J. E., Investigation of Digital Mobile Radio

Communications, (Stock No. 2700-00233, U.S. Government Printing Office,

Washington, D.C., October 1973).

[4] Lucky, R. W., Salz, J., and Weldon, E. J., Jr., Principles of Data Communication

,

(McGraw Hill, New York, N.Y., 1968).

[5] Peterson, W. W., and Weldon, E. J., Jr., Error Correcting Codes, (MIT Press,

Cambridge, Mass., 2d Edition, 1972).

[6] Stein, S., and Jones, J. J., Modern Communications Principles , (McGraw Hill, New

York, N.Y., 1967).

[7] Thomas, J. B., Communication T^ieory , (Wiley, New York, N.Y., 1969).

[8] Urban Sciences, Inc., Final Report on a Study of Digital Communications

Equipment for Law Enforcement t/se , (WeUesley, Mass., October 1973).

23

APPENDIX B

Frequency Response Measurements

2 ,4 .6 .8 1,0 1.2 1.4 1,6 1,8 2,0 2.2 2.4 2.6 2.8 3.0 FREQUENCY (kHz)

Figure Bl. Relative attenuation vs. audio frequency — VHF

25
CD

.2 .4 .6 ,8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2-6 2.8 3.0 FREQUENCY (kHz)

Figure B2. Relative attenuation vs. audio frequency — UHF

Figure B3. Relative envelope delay vs . audio frequency — VHF

26
320

280

.2 .4 .6 .8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 FREQUENCY (kHz)

Figure B4. Relative envelope delay vs. audio frequency — UHF

27

APPENDIX C

Test Results

DOWNTOWN AREA

DATA RATE: 600 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-12/27 FREQ: UHF

Location Speed (mph) Errors

DATA RATE: 600 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/3 FREQ: UHF

Location Speed (mph ) Errors

1 0 0 1 0 0

2 15 1 2 15 0

3 15 0 3 15 0

4 15 0 4 15 0

5 15 0 5 15 0

6 15 0 6 15 0

7 15 0 7 15 0

8 15 0 8 15 0

9 15 0 9 15 0

10 15 0 10 15 0

. 8:00 to 12:00 a.m -12/27 FREQ: VHF-low band Time: 8.00 to 12:00 a.m -1/3 FREQ: VHF-low b

1 0 0 1 0 0

2 15 0 2 15 0

3 15 0 3 15 0

4 15 0 4 20 0

5 15 0 5 20 0

6 15 0 6 0 0

7 15 0 7 15 0

8 15 0 8 15 1 9 15 0

9 15 0

10 15 0 10 15 0

Time: 8:00 to 12:00 a.m.-12/27 FREQ: UHF Time: 8:00 to 12:00 a.m.-l/3 FREQ: UHF

1 0 0

1 0 0

2 15 0 2 15 0

3 15 0

3 15 0

4 15 0 4 15 0

5 15 0 5 20 0

6 15 0 6 20 0

7 15 0 7 25 0

8 15 0 8 20 0

9 12 0 9 20 0

10 15 0 10 15 0

: 8:00 to 12:00 a.m -12/27 FREQ: VHF-low band Time: 8:00 to 12:00 a.m -1/3 FREQ: VHF-low b

1 0 0 1 0 0

2 15 0 2 15 0

3 15 0 3 10 0

4 20 0 4 20 0

5 15 0 5 12 0

6 15 0 20 0

7 15 0 7 30 0

8 20 0 8 15 0

9 15 0 9 15 0

10 15 2 10 10 0

29
DOWNTOWN AREA

DATA RATE: 600 bps MOD: FSK DATA RATE: 1200 bps MOD: FSK

Time: 1:00 to 5:00 p.in.-l/3 FREQ: UHF Time* 1*00 to S'OO n m -1/8 FREQ: UHF

Location Speed (mph ) Errors Location Speed (mph) Errors

1 0 0 1 0 0

2 15 0 2 15 0

3. 15 0 3 15 0 4 20 0 4 15 0

5 . 15 0 5 15 0 6 15 0 6 15 0

7 t; n 71 15 AU

8 20 0 8 15 0

9 15 0 9 15 0

10 15 0 10 15 0

Time: 1:00 to 5:00 p.m.-l/3 FREQ: VHF-low band Time: 1:00 to 5:00 p.m.--1/8 FREQ: VHF--low band

1 0 0 0 0

2 - ' 20 0 2 15 0

3 15 0 3 15 0 4 20 0 4 15 0 5 15 0 5 15 0 6 10 0 6 15 0

'7 0 0 7 15 U 8 15 0 8 15 0 9 15 0 9 5 0

10 15 0 10 15 0 Time: 1:00 to 5:00 p.m.--1/8 FREQ: UHF

1 0 0

2 15 0

3 15 4 15 0 5 25 0

- 6 15 0

7 15 0

8 20 0

9 15 0

10 15 0

Time: 1:00 to 5:00 p.m. I/O FREQ: VHF-low band

1 0 0

2 15 0

3 15 0 4 20 0

5 15 0 6 15 0

7 15 0 8 20 2 9 20 0

10 15 0

30
DOWNTOWN AREA

D \T \ RATE: 1200 bps MOD: FSK

Time: 6:00 to 12:00 p.m.-l/8 FREQ: UHF

Location Speed (mph) Errors

2

1 15GO0

3 15 1 4 15 0

5 15 0

6 15 0

7 10 0

8 15 0

9 15 0

10 10 0

Time: 6:00 to 12:00 p.m.-l/8 FREQ: VHF-low band

1 0 3

2 15 0

3 15 0 4 15 0

5 15 0

6 15 0

7 10 0

8 15 2

9 15 0

10 15 0

Time: 6:00 to 12:00 p.m.-l/8 FREQ: UHF

1 0 0

2 15 0

3 20 0 4 15 0

5 15 0

6 18 0

7 15 0

8 20 0

9 15 0

10 15 0

Time: 6:00 to 12:00 p.m.-l/8 FREQ: VHF-low band

1 0 0

2 15 0

3 20 0

4 25 0

5 20 0

6 0 0

7 15 0

8 15 0

9 15 0

10 15 0

DATA RATE: 1200 bps MOD: FSK

Time: 6:00 to 12:00 p.m.-l/8 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 15 0

3 15 0 4 25 0

5 25 0

6 15 0

7 15 0

8 15 0

9 15 0

10 15 0

Time: 6:00 to 12:00 p.m.-l/8 FREQ: VHF-low band

1 0 0

2 15 0

3 15 0

4 15 0

5 15 0

6 15 0

7 15 0

8 15 0

9 15 0

10 15 1

31
DOWNTOWN AREA

DATA RATE: 1200 bps MOD: DPSK

Time: 6:00 to 12:00 p.m.-l/23 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 15 0

3 15 0 4 15 0

5 15 0

6 15 0

7 15 0

8 15 0 9 20 0

10 15 1 Time: 6:00 to 12:00 p.m.-l/23 FREQ: VHF-low band

1 0 0

2 15 0

3 15 0

4 25 0

5 20 0 6 15 0

7 15 0

8 10 0

9 20 ' 0

10 15 0 Time: 6:00 to 12:00 p.m.-l/23 FREQ: UHF

1 0 0

2 15 0

3 15 0

4 15 0

5 20 0

6 15 0

7 15 0

8 15 0

9 0 0

10 18 0

Time: 6:00 to 12:00 p.m.-l/23 FREQ: VHF-low band

1 0 0

2 15 2

3 15 0

4 15 0

5 15 0

6 15 0

7 18 0

8 20 0

9 .15 0

10 15 0

DATA RATE: 1200 bps MOD: DPSK

Time: 6:00 to 12:00 p.m.-l/23 FREQ: UHF

Location Speed (mph) Errors

1 A0 U

2 20 0

3 15 0 4 15 0

5 0 0 6 20 0

7 18 0

8 10 0 9 15 0

10 15 0

Time: 6:00 to 12:00 p.m.-l/23 FREQ: VHF-low band

1 0 0

2 20 0

3 20 0 4 25 0

5 15 0

6 10 0

7 15 0

8 15 2 9 15 0

10 15 0

: 1:00 to 5:00 p.m.-l/24 FREQ: UHF

1 0 0

2 15 0

3 20 0 4 25 0

5 15 0

6 15 0

7 15 0

8 0 0 9 15 0

10 15 0

Time: 1:00 to 5:00 p.m.-l/24 FREQ: VHF-low band

1 0 0

2 20 0

3 20 0 4 20 0

5 22 0

6 15 0

7 15 0

8 20 2 9 15 0

10 15 2

32
DOWNTOWN AREA

DATA RATE: 1200 bps MOD: DPSK

Time: 1:00 to 5:00 p.m.-l/24 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 20 0

3 15 0

4 25 0

5 15 0 6 15 0

7 15 0 8 15 0

9 15 0

10 15 0

Time: 1:00 to 5:00 p.m.-l/24 FREQ: VHF-low band

1 0 0

2 15 0

3 15 0

4 15 0

5 25 0

6 15 0

7 0 0

8 15 0

9 15 0

10 20 0

DATA RATE: 1800 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/16 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 15 0

3 15 0

4 15 0

5 20 0

6 15 0

7 15 0

8 15 0

9 15 0

10 15 0

Time: 8:00 to 12:00 a.m.-l/16 FREQ: VHF-low band

1 0 0

2 15 0 3 20 " 4 5 ^

5 18 0 6 15 0

7 ' . 0

8 o 0

9 18 0

10 15 0

Time: ".^i 10^ 12:00 a.m.-l/16 FREQ: UHF

0

2 10 0

3 16 0

4 20 0

5 20 0

6 15 0

7 15 0

8 20 0

9 15 0

10 15 1

Time: 8:00 to 12:00 a.m.-l/16 FREQ: VHF-low band

1 0 0

2 15 0

3 10 0 4 15 0

5 25 3 6 20 0

7 15 0

8 15 0

9 10 0

10 10 0

33
DOWNTOWN AREA

DATA RATE: 1800 bps MOD: FSK

Time: 1:00 to 5:00 p.m.-l/16 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 12 0

3 15 0 4 20 0

5 25 0

6 16 2

7 0 0

8 0 0 9 15 0

10 15 0 Time: 1:00 to 5:00 p.m.-l/16 FREQ: VHF-low band

1 0 0

2 15 0

3 15 0

4 15 0

5 20 0

6 12 0

7 5 0

8 15 0

9 20 0

10 15 0 Time: 1:00 to 5:00 p.m.-l/16 FREQ: UHF

1 0 0

2 20 0

3 15 1 4 10 0

5 15 0

6 15 0 7 10 0

8 18 0

9 15 0

10 15 0 Time: 1:00 to 5:00 p.m.-l/16 FREQ: VHF-low band

1 0 0

2 15 0

3 0 0

4 20 0

5 15 0

6 15 0

7 15 0

8 15 3 9 20 0

10 15 0

DATA RATE: 1800 bps MOD: FSK

Time: 1:00 to 5:00 p.m.-l/16 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 15 0

3 15 0 4 15 0

5 20 0 6 10 0

7 0 0

8 15 0

9 15 0

10 15 0

Time: 1:00 to 5:00 p.m.-l/16 FREQ: VHF-low band

1 0 0

2 15 0 3 15 0

4 15 0

5 20 0

6 0 0

7 15 0 8 15 0 9 15 0

10 15 0

34
DOWNTOWN AREA

DATA RATE: 2400 bps MOD: DPSK

Time: 8:00 to 12:00 a.m.-l/28 FREQ: UHF

Location Speed (mph ) Errors

DATA RATE: 2400 bps MOD: DPSK

Time: 8:00 to 12:00 a.m.-l/28 FREQ: UHF

Location Speed (mph ) Errors

1 0 2

2 15 0

3 15 0

4 15 0

5 15 0

6 15 0

7 10 0

8 5 0

9 15 0

10 15 0

iTime: 8:00 to 12:00 a.in.-l/28 FREQ: VHF-low band

1 0 0

2 10 0

3 20 0 4 15 0

5 18 0

6 20 0

7 10 0

8 15 2 9 15 0

10 15 0

Time: 8:00 to 12:00 a.in.-l/28 FREQ: UHF

1 0 0

2 15 0

3 20 0

4 10 0

5 15 0

6 15 0

7 5 0

8 15 0

9 15 0

10 20 0

rime: 8:00 to 12:00 a.ni.-l/28 FREQ: VHF-low band

1 0 0

2 0 0

I 3 15 0

4 15 0

5 20 0

6 10 0

7 15 0

8 25 0 (19 20 0

I 10 10 0

1 0 u

2 15 0

3 10 0

4 15 0

5 20 0 6 0 0

7 15 0

8 20 0

9 15 0

10 15 0

Time: 8:00 to 12:00 a.m.-l/28 FREQ: VHF-low band

1 0 0

2 15 0

3 15 0 4 10 5

5 15 0 6 15 0

7 15 0

8 0 1 9 15 0

10 15 0

: 1:00 to 5:00 p.m -1/28 FREQ: UHF

1 0 0

2 15 0

3 15 0 4 15 0

5 15 0

6 20 0

7 10 0

8 15 0 9 5 0

10 15 0

Time: 1:00 to 5:00 p.m.-l/28 FREQ: VHF-low band

1 0 0

2 15 0

3 15 0

4 15 0

5 15 0

6 15 0

7 15 0

8 15 0

9 15 0

10 15 0

35
DOWNTOWN AREA

DATA RATE: 2400 bps MOD: DPSK

Time: 1:00 to 5:00 p.m.-l/28 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

2 15 0

3 20 0

4 25 0

5 25 0

6 20 0

7 12 0

8 20 0

9 10 0

10 15 0 Time: 1:00 to 5:00 p.m.-l/28 FREQ: VHF-low band

1 0 0

2 15 0

3 20 0

4 20 0

5 25 0

6 20 0

7 20 0

8 15 0

9 15 0

10 15 0

36
DATA RATE: 600 bps

SOUTH SUBURBAN ROUTE

MOD: FSK DATA RATE: 1200 bps MOD: FSK

Time: 1:00 to 5:00 p.in.-12/27 FREQ: UHF

Location Speed (mph) Errors

1 0 0 20 1 30 0

2 0 0 20 0

30 0

3 0 0

20 0

30 0

4 0 0

30 0

40 0

5 0 0

30 0

45 0

6 0 0 20 0

35 0

7 0 0

Time: 8:00 to 12:00 a.m.-l/2 FREQ: VHF-low band

1 0 0 20 0 35 0

2 0 0

15 0

30 0

3 0 0 20 0 35 0

4 0 0

20 0 35 0

5 0 0 20 0 35 0

6 0 0

25 0

35 0

7 0 0

Time: 8:00 to 12:00 a.m.-l/9 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

20 0 35 0

2 0 0

15 0 30 0

3 0 0

20 0

30 0

4 0 0 20 0

35 0

5 0 0

30 0

40 0

6 0 4

25 2 35 3

7 0 0

Time: 1:00 to 5:00 p.m.-l/lO FREQ: VHF-low band

1 0 0 20 0 40 0

2 0 0

20 0

30 0

3 0 0

20 0

30 0

4 0 0

15 0

40 0

5 0 0

25 0

30 0

6 0 0

30 0

40 0

7 0 0

37
SOUTH SUBURBAN ROUTE

DATA RATE: 1200 bps MOD: DPSK

Time: 8:00 to 12:00 a.m.-l/23 FREQ: UHF

Location Speed (mph) Errors

1

'

' AU 0 ZU U oU nU

nZ U U on AU

QnoU AU

AuAU 20 Q 35 n 4 0 0 10 0 20 0

5 0 0 20 0 35 0 6 r 0 0

15 2 30 2

7 0 0

6:00 to ]2:00 p.m -1/24 FREQ: VHF-low 1

I 0 0

15 0

35 Q

2 0 0

5 0

25 0

3 0 0 zu nV

n

A»

A A

10 0 20 0

5 0 0

10 0

20 0

6 0 0 20 0

35 2

7 0 0

DATA RATE: 1800 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/12 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

OA 0

Ob A0

o A 1 OA At

oo o

ooAuAU

AU dn**u A\3 4 0 0 30 0 40 0

5 0 0

20 0 30 0

6 0 1 15 2 30 2

7 0 0

8:00 to 12:00 a.m -1/14 FREQ: VHF-low

\ Q Q 20 \0

2 0 0

Q 30 0

o

<> nV Q

Zd AUnU

4

A

u Au

30 0 40 0

5 0 0 20 0 40 0

6 0 0 20 0 35 0

7 0 0

38
SOUTH SUBURBAN ROUTE

DATA RATE: 2400 bps MOD: DPSK

Time: 8:00 to 12:00 a.m. -2/1 FREQ: UHF

Location Speed (mph) Errors

.1 0 0 20 0

35 2

2 G O 20 0 35 0

3 0 0 20 0

35 0 4 0 0 20 0

35 0

5 0 0

20 2 30 4

6 0 0 20 0 30 0

7 0 0 Time: 8:00 to 12:00 a.m.-2/2 FREQ: VHF-low band

1 0 0

15 0 30 0

2 0 0 20 0

35 0

3 0 0

20 0 30 0

4 0 0

5 0

35 0

5 0 0 20 0

40 0

6 0 0 20 2 25 0

7 0 0

39
SOUTH SUBURBAN ROUTE

DATA RATE: 600 bps MOD: FSK

Time: 1:00 to 5:00 p.ra.-l/2 FREQ: UHF

Location Speed (mph) Errors

8 0 0

20 3 30 0

9 0 0

10 0 30 0

10 0 0 20 0

30 0

11 0 0 20 0 30 0

12 0 0 30 0 40 0

13 0 0

15 6

30 6

14 0 0

20 i 32 1 15 0 0

20 6

35 3

16 0

20

30

0

r 00

17 0 0

20 0

45 0

DATA RATE: 600 bps MOD: FSK

Time: 8:00 to 12:00 a.in.-12/28 FREQ: VHF-low ban

Location Speed (mph ) Errors

8 0 0 20 5 40 2 9 0 0

15 0 30 1 10 0 0

20 0

30 2

11 0 0

20 3 40 0

12 0 0

20 0

30 0

13 0 0

25 0 30 1 14 0 0

25 1 40 0

15 20GO4 30 3

16 0 0

20 0 30 0

17 0 0 20 0 50 0

40
SOUTH SUBURBAN ROUTE

DATA RATE: 1200 bps MOD: FSK

Time: 6:00 to 12:00 p.m.-l/lO FREQ: UHF

Location Speed (mph) Errors

DATA RATE: 1200 bps MOD: FSK

Time: 1:00 to 5:00 p.m. -2/9 FREQ: VHF-low band

Location Speed (mph) Errors

8 0 0 8 0 0 20 2 10 2 35 1 25 0

9 0 0 9 0 0 20 0 10 1 30 0 25 0

10 0 0 10 0 0

25 0 30 0 35 0 40 0

11 0 0 11 0 0

10 0 20 1 25 0 30 1 12 0 0 12 0 0

30 0 10 0 40 0 25 0

13 0 0 13 0 0

25 1 20 1 30 0 40 0

14 0 0 14 0 0

15 2 15 0 25 0 30 1 15 0 1 15 0 0

20 7 15 4

30 2 25 3

16 0 0 16 0 0

15 0 20 0 30 0 40 0

17 0 0 17 0 0

5 0 20 2

20 0 35 0

41
SOUTH SUBURBAN ROUTE

DATA RATE: 1200 bp8 MOD: DPSK DATA RATE: 1200 bps MOD: DPSK

Time: 8:00 to 12:00 a.in.-l/25 FREQ: UHF Time: 1:00 to 5:00 p.m.-l/23 FREQ: VHF-low band

Location Speed (mph ) Errors Location Speed (mph ) Errors

8 0 0 8 0 0

10 0 15 4 40 0 35 3 9 0 0 9 0 0

15 0 10 0

25 0 25 2 10 0 0 10 0 0 20 0 15 0 30 0 25 0

11 0 0 11 0 0

12 0 10 0

30 0 15 0

12 0 0 12 0 0 20 0 15 0

35 0 25 0

13 0 0 13 0 0

5 0 10 0

25 0 30 2

14 0 0 14 0 0

10 2 20 1 35 2 25 0

15 0 0 15 0 0

15 4 10 2 25 3 25 2

16 0 0 16 0 0

10 0 20 0 35 0 30 0

17 0 0 17 0 0

20 0 10 0 30 0 25 2

i

I

42
SOUTH SUBURBAN ROUTE

DATA RATE: 1800 bps MOD: FSK

Time: 1:00 to 5:00 p.m.-l/U FREQ: UHF

Location Speed (mph) Errors

8 0 0

15 3 30 1 9 0 0

15 0 30 1 10 0 0 30 0

40 1 11 0 0

20 0 30 2

12 AU A

15 A

25 A

13 0

Au

15 0

30 0

14 Au

25 A 35 0

15 0 2 20 1 35 6

16 0 0

15 0 30 0

17 0 0

15 0

25 0

DATA RATE: 1800 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/12 FREQ: VHF-low band

Location Speed (mph ) Errors

8 0 0

15 0

30 0

9 0 0

20 0

30 2

10 0 0 30 0

40 0

11 0 0

25 0

40 0

12 0 0

15 AU 30 0

13 0

A0

15 0

35 0

14 0 0

15 0

30 1 15 0 0

20 1 35 2

16 0 0

15 0

30 0

17 0 0

20 3 40 1

43
DATA RATE: 2400 bps

SOUTH SUBURBAN ROUTE

MOD: DPSK DATA RATE: 2400 bpi MOD: DPSK

Time: 1:00 to 5:00 p.m.-2/2 FREQ: UHF

Location Speed (mph ) Errors

8 0 0

25 0 40 4

9 0 0

20 0

35 0

10 0 0

l r 10 0

35 0

1

0 0

16 0

45 0

1

u 0

1 c lO Au

OO 8

13 gxu

ZD 0

1 14 AU A

ZD (15

15 0 0

15 0

40 4

16 0 0

15 0

35 0

17 0 Q

35 0

50 2

Time: 8:00 to 12:00 a.m. -2/1 FREQ: VHF-low band

Location Speed (mph) Errors

8 0 0 20 0

35 0

9 0 0

15 0

35 0

10 0 0

15 0

35 0

11 0 0

15 0 30 0 0 0

9A AU OA 0

1 3 A 0 25 0 40 0

A A

OAZU 0 30 0

15 0 0

15 2 40 2 16 0 0

15 5 30 0

17 0 0 20 0 45 2

44
SOUTH SUBURBAN ROUTE

DATA RATE: 600 bps MOD: FSK DATA RATF- l^nflKn 8 MOD: FSK

Time: 1:00 to 5:00 p.m.--12/28 FREQ: UHF Time: 8:00 to 12:00 a.m.-1/10 FREQ: UHF

Location Speed (mph) Errors Location Speed (mph) Errors

18 u U 18 0 0

OA Au 25 u W A

u 40 Au

19 fxu

Au 19 0 u oo AU 20 1 CA 11 40 u

on U- AU 20 0 u

QA A 20 AU

c^A AU 40 A

tl U

AU 21 0 AU

30 0 30 0

45 0 45 0

22 0 0 22 0 0

15 0 20 0

25 0 35 0

Time: 6:00 to 12:00 p.m -1/2 FREQ: VHF-low band lime: o:UU to IZ.W p.m —1/lU rnc-y: VHF -low ba

io AU

Au 18 0 nu

zo n\3 20 Q to A\3 35 0

1Q n\i AVf 19 0 0 9A A\3 15

1 35 0

AU

AU 20 0 0

Q 25 0

Q 45 0

91 nu

AV 21 0 0

zU AU 30

40 0 45 0

22 0 0 22 0 0

! 20 0 15 0

30 0 35 0

45
SOUTH SUBURBAN ROUTE

DATA RATE: 1200 bps MOD: DPSK DATA RATE: 1800 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/24 FREQ: UHF Time: 1:00 to 5:00 p.m.-l/12 FREQ: UHF

Location Speed (mph) Errors Location Speed (mph) Errors

18 0 0 18 0 0

15 0 20 0 40 0 50 1 19 0 0 19 0 0 20 0 15 0 30 0 40 0 20 0 0 20 0 0 20 2 20 0 25 0 40 0 21 0 0 21 0 0 15 0 30 0 25 0 45 0 22 0 0 22 0 0 20 0 25 1 30 0 40 0

: 1:00 to 5:00 p.m. -1/25 FREQ: VHF-low band Time: 1:00 to 5:00 p.m -1/14 FREQ: VHF-low ht

0 0

1

Q

U U

OA AU

nvl u

nu

1Q nU A

T 10 nu u

13 0 u

OO 0 u

U 0

on u

Au

20 0 25 0 45 0 45 0

21 0 0 21 0 0

15 0 35 0 40 0 45 0 22 0 0 22 0 0 10 0 15 0 25 0 30 0

46
SOUTH SUBURBAN ROUTE

DATA RATE: 2400 bps MOD: DPSK

Time: 1:00 to 5:00 p.m.-2/l FREQ: UHF

Location Speed (mph ) Errors

18 0 0 20 0

50 0

19 0 0

40 0 45 0

20 0 0 25 2 40 0

21 0 0

25 0 40 0

22 0 0 30 0 40 0 Time: 1.00 to 5:00 p.m.-2/2 FREQ: VHF-low band

18 20GO0 45 0

19 0 0 30 0 45 0 20 0 0 25 0 50 0

21 0 0 25 0 30 0

22 0 0 20 0 30 0

47
NORTH SUBURBAN ROUTE

DATA RATE: 600 bps MOD: FSK

Time: 8:00 to 12:00 a.in.-l/4 FREQ: UHF

Location Speed (mph ) Errors

1 0 0 20 0 30 0

2 0 0

15 0 25 0

3 0 0 20 0 30 0

4 0 0

10 0 25 0

5 0 0

15 0 30 0

6 0 0

10 0 20 0 Time: 1:00 to 5:00 p.m.-l/3 FREQ: VHF-low band

1 0 0

15 0 30 0

2 0 0 20 0 40 0

3 . 0 0

5 0

15 0 4 0 0

15 0 35 0

5 0 0 20 0 25 0 6 0 0

15 0 30 0

DATA RATE: 1200 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/7 FREQ: UHF

Location Speed (mph) Errors

11 U

A

U An

oz nU

zo ftAu

o Q

AV

15 0 32 0

4 0 0

15 0 35 1 co U

A

cO A

Q C OO A

o U A

15 AU 30 0

8:00 to 12:00 a.m. -1/11 FREQ: VHF-low 1

1 0 0 20 0

35 1 2 0 0 20 0 40 0

3 0 0

15 0 oO A\J 4 0 0 25 0 35 0

5 0 0

15 0 30 0 6 0 0

15 0 30 0

48
DATA RATE: 1200 bps

NORTH SUBURBAN ROUTE

MOD: DPSK DATA RATE: 1800 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/22 FREQ: UHF

Location Speed (mph) Errors

1 0 0 25 0

40 0

2 0 0

15 0

25 0

3 0 0

15 0

40 0

, 4 0 0

15 0

I 30 0

5 0 0 20 0 40 0

6 0 0 20 0 40 0

Time: 8:00 to 12:00 a.m.-l/21 FREQ: VHF-low band

1 0 0

15 0 20 0

2 0 0

10 0

25 0

3 0 0

20 0

25 0

4 0 0

i 15 0

; 40 0

I 5 0 0

S 15 0

i| 40 0

I 6 0 0

I 25 0 35 0

Time: 8:00 to 12:00 a.m.-l/15 FREQ: UHF

Location Speed (mph ) Errors

1 0 0

25 0

30 0

2 0 0

15 0

40 0

3 0 0

10 0

35 0 4 0 0

20 0

30 0

5 0 0

5 0

15 0

6 0 0

20 0

35 2 Time: 8:00 to 12.00 a.m.-l/18 FREQ: VHF-low band

1 0 0

5 0

40 0

2 0 0

15 0

25 0

3 0 0

25 0 35 0

4 0 0

30 0

40 0

5 0 0

15 0

30 0

6 0 0

10 0

35 0

!

49
NORTH SUBURBAN ROUTE

DATA RATE: 2400 bps MOD: DPSK

Time: 8:00 to 12:00 a.m.-l/30 FREQ: UHF

Location Speed (mph) Errors

1 0 0

15 1 30 0

2 0 0 20 0 40 0

3 0 0 20 0

45 0

4 Q

15 0

35 0

5 0 0 20 0 40 0 6 0 0

15 0

30 0

8:00 to 12:00 a.m -1/31 FREQ: VHF-low 1

1 0 0 20 0 30 0

2 0 0 20 0 40 0

3 0 0

20 0 35 0

4 0 0

15 0

30 0

5 0 0 25 0 45 0 6 0 0 20 0 35 0

50
NORTH SUBURBAN ROUTE

DATA RATE: 600 bps MOD: FSK DATA RATE: 1200 bps MOD: FSK

Time: 6:00 to 12:00 p.m.-1/3 FREQ: UHF Time: 1:00 to 5:00 p.m.-l/ll FREQ: UHF

Speed (mph) Errors Location Speed (mph ) Errors

7 u I u U

15 U

OA U

30 U 09 A 8 0 U o U

A\J

1 25 9 9n A

1 35 1 3Coo O 9 0 ll O» Au

O

z 20 o ZU eO 35

1 0 AU in n 9

,1 20 0 aU 0 35 O

i 0 U 111 J. nu

20 O ZU Aw

1 35 A 0

'1 12 0

nu 12 0 0 20 in 1 35 U

AV

0

AU 14lO nu 0

20 Au zu9(1 Q

35 Au 40 3

! 0

AU Id 0 38

15 14 15 27

i 35 6 30 42

|Time: 8:00 to 12:00 a.m.-1/4 FREQ: VHF-low band

1 7 0 0

i 20 0

I 30 0

8 0 0

20 0 40 0

9 0 0

20 0

35 0

10 0 0

25 1 35 0

11 0 0

15 0

1 30 0

12 0 0 20 0

35 0

13 0 0

15 2 30 0

14 0 0

20 0

35 0

51
DATA RATE: 1200 bps

NORTH SUBURBAN ROUTE

MOD: FSK DATA RATE: 1200 bps MOD: DPS

Time: 1:00 to 5:00 p.m -1/7 FREQ: VHF--low band Time: 1.00 to 5:00 p.m -1/21 FREQ: UHF t Location Speed, (mph) Errors Speed (ntph) Errors t

7 0 0 7 0 20 0 20 4 30 0 35 3 8 0 0 8 0 0 1 20 0 15 3

- 35 0 25 2 9 0 0 9 0 0

15 2 25 3 30 0 40 4

10 0 0 10 0 0 1 25 2 30 7 35 0 40 5 , 11 0 7 11 0 2 25 0 15 0 35 0 30 0

12 0 0 12 0 0 20 0 15 2 40 1 35 0

13 0 0 13 0 0 30 3 15 2 40 2

o c 6b u

14 0 0 14 0 4

15 1 15 12 30 0 30 21

52
NORTH SUBURBAN ROUTE

DATA RATE: 1200 bps MOD: DPSK

Time: 1:00 to 5:00 p.m.-l/22 FREQ: VHF~low band

I Location Speed (mph) Errors

I U U

1 C u

nu

ao n nU

20

Au

9 0 n

10 0

25 0

10 0 0

15 0 35 0

11 0 0

20 3 30 0

12 0 0

5 0

25 0

13 0 0 20 2 35 2

14 0 0

15 2 30 0

I

DATA RATE: 1800 bps MOD: FSK

Time: 1:00 to 5:00 p.m.-l/18 FREQ: UHF

Location Speed (mph ) Errors

7 0 0 20 17 35 14 8 0 0 25 5 35 4

9 0 1 25 6

35 4

10 0 4

15 26

35 14

11 0 0

20 5 30 4

12 0 2 20 5 35 0

13 0 0

20 4

30 2

14 0 25

15 42 30 27 Time: 1:00 to 5:00 p.m.-l/15 FREQ: VHF-low band

7 0 0

25 0

35 0

8 0 0

15 1 40 0

9 0 0

15 0 35 0

10 0 0

20 3

35 0

11 0 0

20 0

30 3

12 0 0

15 0 25 0

13 0 0

20 3 35 0

14 0 0

20 5 35 9

53
NORTH SUBURBAN ROUTE

DATA RATE: 2400 bps MOD: DPSK

Time: 1:00 to 5:00 p.m.-l/31 FREQ: UHF

Location Speed (mph ) Errors

7 0 0

20 14 35 12 8 0 0 20 5 40 4

9 0 0

30 5 35 5

10 0 0

30 20 35 15

11 0 0

15 0

30 8

12 0 0

20 11 35 0

13 0 0

15 0

35 0

14 0 0

30 6

40 4 Time: 1:00 to 5:00 p.m.-l/30 FREQ: VHF-low band

7 0 0

15 0

35 0

8 0 0

15 0 40 2 9 0 0

15 0

35 0

10 0 0

10 0

30 0

11 0 0

10 0

30 0

12 0 0

15 0

35 0

13 0 0

20 0

35 0

14 0 0 30 8 35 7

54
NORTH SUBURBAN ROUTE

DATA RATE: 600 bps MOD: FSK

rime: 1:00 to 5:00 p.m.-l/4 FREQ: UHF

I Location Speed (mph) Errors

15 0 0

20 7

16 0 2 20 6 30 4

17 0 0

15 2 30 1 18 0 0

10 1 35 0

19 0 0

20 0 40 0

20 0 0

15 0 30 0

21 0 0

15 0

30 0

22 0 0 20 0

30 0

23 0 0

15 0

30 0

'ime: 6:00 to 12:00 p.m.-l/3 FREQ: VHF-low band

15 0 0 20 0

30 0

16 0 0

15 0

30 0

17 0 0

15 0 30 0

18 0 0 20 0

30 0

19 0 0

10 0 35 0

20 0 0

20 0

35 0

21 0 0

15 0

35 0

22 0 0

15 0 35 0

23 0 0

10 0

30 0

DATA RATE: 1200 bps MOD: FSK

Time: 8:00 to 12:00 a.m.-l/8 FREQ: UHF

Location Speed (mph ) Errors

15 0 0

20 1 35 3

16 0 12 30 6 40 0

17 0

' 0 20 4

35 2

18 0 0

15 0

40 1 19 0 0 20 0

35 0

20 0 0 20 0

40 0

21 0 0 20 0

30 0

22 0 0

20 0

35 0

23 0 0

20 0

30 0

55
NORTH SUBURBAN ROUTE

DATA RATE: 1200 bps MOD: DPSK

Time: 1:00 to 5:00 p.in.-l/21 FREQ: VHF-low band

Location Speed (mph ) Errors

15 0 0 20 0

35 0

16 0 0

15 0 20 0

17 0 0

15 3 30 2

18 0 0 20 0 35 0

19 0 0

15 0

25 0 20 0 0 20 0 30 0

21 0 0

15 0

25 0

22 0 0 20 0 35 0

23 0 0

25 0 35 0

DATA RATE: 1200 bps MOD: DPSi

Time: 1:00 to 5:00 p.m.-l/22 FREQ: UHF

Location Speed (mph) Errors

15 20 12

16 0 0

25 10 30 6

17 0 0

15 2 30 0

18 0 0 20 2 40 0

19 0 0

15 0 30 0 20 0 0 20 0 35 0

21 0 0 10 0 25 0

22 0 0

15 0 35 0

23 0 0 20 0 35 0 I

56
NORTH SUBURBAN ROUTE

DATA RATE: 1200 bps MOD: FSK DATA RATE: 1800 bps MOD: FSK

"ime: 1:00 to 5:00 p.m.-l/ll FREQ: VHF-low band Time: 6:00 to 12:00 p.tn.-l/15 FREQ: UHF

Location Speed (mph ) Errors Location Speed (mph ) Errors

15 0 0 15 0 0 20 0 25 2 40 0 35 5

16 0 0 16 0 5 25 0 20 17 40 0 40 7

17 0 2 17 0 0 20 0 15 14 40 0 35 6

18 0 0 18 0 0

20 1 20 2 40 0 35 0

19 0 0 19 0 0 20 0 25 0 30 0 40 0

20 0 0 20 0 0 30 0 15 3 45 0 35 0

21 0 0 21 0 0

1 ^ ^ u 20 0* 35 0 35 0

22 0 0 22 0 0

20 0 20 0

25 0 30 0

23 0 0 23 0 0

15 0 20 0

25 0 35 0 Time: 1:00 to 5:00 p.m.—1/11 FREQ: VHF-low ba

15 0 0

25 0

35 0

16 0 0

20 5 35 2

17 0 0 20 1 30 0

18 0 0

15 3 35 1 19 0 0

20 0

35 0

20 0 0

20 0

30 0

21 0 0

15 0

35 0

22 020 0

25 0

23 0 0

15 0

35 0

57
NORTH SUBURBAN ROUTE

DATA RATE: 2400 bps MOD: DPSK

Time: 6:00 to 12:00 p.m.-l/30 FREQ: UHF

Location Speed (mph ) Errors

15 20 42

16 0 58 40 38

17

"0 0 20 5 40 12 18 0 0 15 0 40 0

ioly u u oo Au wAl\ AU

Au

OA oZ 40 0

21 0 0

20 0

30 0

22 0 0

20 0

30 0

23 0 0

20 0

25 0

: 6:00 to 12:00 p.m.-l/31 FREQ: VHF-low

15 0 0

20 0

35 0

16 0 0 20 0 40 0

17 0 0 20 0 40 0

18 0 0

15 0 40 2 19 0 0 30 0 47 0 20 0 0 30 0

45 0

21 0 0 30 0 35 0

22 0 0

30 0 35 0

23 0 0 20 0 30 0

58
TIME OF DAY DATA

DATA RATE: 1200 bps MOD: FSK

DOWNTOWN AREA

Time o{ day variations are included in the original data. SOUTH SUBURBAN

Time: 6:00 to 12:00 p.m.-l/16 FREQ: UHF

Location Speed (mph ) Errors

020

35

0 Time: 8.00 to 12:00 a.m.-l/18 FREQ: UHF

020

35 Time: 6:00 to 12:00 p.m. -1/16 FREQ: VHF low band

025

350

0

1525

Time: 8:00 to 12:00 a.m.-l/18

Location

NORTH SUBURBAN

FREQ: UHF

Speed (mph ) Errors

7 0 0

7 20 3

7 35 2 8 0 0

8 20 3 8 30 2 9 0 1 9 20 5

9 30 3

8.00 to 12:00 a.m -1/18/74 FREQ: VHF loi

7 0 0

7 20 0

7 30 0 8 0 0

8 20 0

8 35 0

9 0 0

9 20 1 9 30 0

59

<r U.S. GOVERNMENT PRINTING OFFICE : 1977 0-214-513
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