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Interoperable Emergency Communications Training INTEROP03 Radio Operations Unit 1

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Title: Interoperable Emergency Communications Training INTEROP03 Radio Operations Unit 1


1
Interoperable Emergency Communications
TrainingINTEROP03Radio OperationsUnit 1
Technology Issues and Concepts
  • STATE OF ALASKADivision of EnterpriseTechnology
    Services

2
Objectives
  • Describe technologies in use today for public
    safety communications systems throughout Alaska
  • Understand advantages and shortcomings of
    different technologies

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Technology
  • Technology refers to
  • Equipment/infrastructure
  • Network
  • Software applications
  • Public safety agencies use technology to exchange
    critical information when responding to
    incidents.

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Radio Signals
  • Radio waves travel in straight lines (line of
    sight). Terrain and other barriers can block
    signals.
  • Radio waves lose strength over distance.
  • Radio signals are boosted to increase signal
    strength and extend coverage range.

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Radio Waves
  • Radio waves are a repeating stream of peaks and
    valley
  • Wavelength is the measurement of distance from
    one point to another equal point in the wave
    (either peak to peak, or valley to valley)

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Radio Waves
  • Cycle is the entire pattern of the wave before it
    repeats itself
  • Frequency is the number of cycles that occur each
    second

1 Second
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Radio Spectrum
  • Frequencies are measured in Hertz (Hz) one
    Hertz is one cycle per second.
  • Kilohertz (KHz)
  • One thousand cycles per second
  • Megahertz (MHz)
  • One million cycles per second
  • Gigahertz (GHz)
  • One billion cycles per second

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Analog Radio
  • Analog can produce static, fading, and feedback

No Noise
Some Noise
Occasional Repetition
Frequent Repetition
Improving Audio Quality
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Digital Radio
  • Digital may sound metallic or fake, does not
    reproduce certain sounds properly, receives all
    or none

No Noise
Improving Audio Quality
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Radio System Architectures
  • Conventional

Trunked
Hybrid
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Conventional System Elements
  • Central Dispatch Dispatcher transmitting from a
    fixed base station. Can transmit to and receive
    from mobile units.
  • Mobile Units Portable and mobile radios used
    in the field.

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Transmitters, Receivers and Repeaters
  • Transmitter radio device that generates and
    emits a radio wave.
  • Receiver radio device that receives a radio
    wave.
  • Repeater device that receives a radio wave and
    re-transmits that wave

NOTE All devices on ALMR are TRANSCEIVERS a
combination of transmitters and receivers.
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Conventional Systems
  • Conventional uses preset/designated frequencies
  • Simplex
  • Repeater
  • Talk around (radio programmed with the repeater
    frequency can have direct communications with
    another radio without going through the repeater)

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Simplex
  • Simplex Conventional radios selected to both
    receive and transmit on a single frequency that
    never changes

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Simplex
  • Simplex Applications
  • Point to Point
  • Portables
  • Mobiles
  • Base Stations with or without remotes (consoles)

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Repeaters
  • Repeater Half-duplex radios selected to receive
    on one frequency and re-transmit on another
    frequency. The frequencies are a licensed pair
    and do not change.

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Repeaters
  • Repeater
  • Mountain tops, towers, and tall buildings
  • Higher power longer distances and better
    coverage
  • May be linked together to extend coverage

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Talkaround
  • Direct or Talkaround - transmitting on the
    repeater frequency to bypass the high power radio
    in the middle.
  • Can be programmed as a button typically added as
    a new channel

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Conventional Systems
  • Similar to a grocery store line
  • Users can only talk when their channel is clear
    to traffic

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Conventional Systems
DOT
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Conventional System Characteristics
  • Only one user at a time can transmit on a
    channel.
  • Users make manual channel selections.
  • Requires user discipline (wait for a free
    channel).
  • Call delay and call blocking increase during peak
    periods.

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Conventional System Types
Simplex
Half Duplex
Full Duplex
  • Uses 2 frequencies
  • Allows simulta- neous Tx and Rx
  • Radios are costly, use more battery power
  • Uses 2 frequencies
  • No simultaneous Tx and Rx
  • Allows base station to repeat/ amplify
    signal
  • Uses 1 frequency
  • No simultaneous transmission (Tx) and
    reception (Rx)

Most commonly used for public safety
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Typical Half-Duplex System
  • Dispatchers Tx frequency is the mobiles Rx
    frequency, and vice versa.

F1 Dispatcher Tx Mobile Rx F2
Mobile Tx Dispatcher Rx
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Trunked System
  • An electronically controlled system in which
  • A few channels are shared by many users.
  • Users can simultaneously receive and transmit.
  • User waiting times are minimal.
  • There are different types of trunked systems. We
    will look at a centralized system as an example.

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Trunked Systems
  • Trunked uses a computer to assign frequencies,
    as needed.
  • Each radio is recognized by the computer/Site
    Controller

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Trunked Systems
  • In a trunked radio system, channels are referred
    to by a Talkgroup ID as opposed to a frequency
  • The IDs are represented by a name in the radio
    called an alias

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Trunked Systems
  • Each radio gets its Site Controller information
    from the Control Channel.
  • Control Channel does not send audio traffic, it
    sends passive information (radio ID, talkgroup
    ID, and channel assignments)

1 2
3 4 Four-Channel
Trunked System
Central (Zone) Controller
Control Channel
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Trunked Systems
  • When the user presses Push-to-talk (PTT), the
    Site Controller determines which radios on that
    talkgroup need to hear the broadcast
  • The Controller assigns a frequency set at each
    repeater needed to accomplish transmission, then
    releases the frequency after the transmission is
    complete

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Trunked Systems Queuing
  • Similar to a bank teller line
  • Users are directed to the first available channel

NOTE Trunking allows many talkgroups to utilize
a limited number of repeaters.
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Trunked Systems
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Trunked System Elements
  • Trunking repeaters Multiple repeaters
    retransmit the radio signals. One repeater serves
    as the data (control) channel, the rest as voice
    channels.
  • Central controller A computer directs
    transmission traffic and assigns available voice
    channels as needed.
  • Mobile units - Portable and mobile radios are
    used in the field. Each is part of a talk
    group.

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Hybrid System
  • Conventional and trunked features in a single
    system.
  • Radios are programmed to operate in conventional
    mode, trunked mode, or both.
  • Conventional channels can be used to avoid call
    setup delay.
  • Cost advantages
  • Trunked mode serves areas of high user density.
  • Conventional sites can be placed in low density
    areas to save costs.

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Whats the Problem?
  • Advances in technology have made it easy for
    people to stay connected.
  • But for public safety agencies, talking to each
    other continues to be a major problem.
  • Why?

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Project 25 (P25)
  • A set of standards for the manufacture of digital
    radios that are compatible with analog FM radios.
  • P25-compliant radios
  • Talk to analog radios in analog mode.
  • Talk to other P25 radios in digital or analog
    mode.

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Radio Spectrum
  • Finite
  • Fragmented
  • Limited by Technology

The bands used by public safety agency radios are
spread widely across the spectrum, making
interagency communication difficult.
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Propagation and Band Characteristics
  • VHF Low Band (30-50 MHz)
  • Best propagation in undeveloped and hilly
    terrainPoor building penetration
  • VHF High Band (150-174 MHz)
  • Very good propagation in undeveloped and hilly
    terrainModerate building penetration
  • UHF (450-512 MHz)
  • Good propagation in undeveloped and hilly
    terrainGood building penetration
  • 700/800 MHz
  • Poor propagation in undeveloped and hilly
    terrainVery good building penetration
  • 700 currently subject to incumbent television
    stations in some areas
  • 800 currently subject to interference from
    commercial carriers

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2004 FCC Narrowbanding Mandate
  • on or before (revised) January 1, 2013 all
    existing licensees on the VHF and UHF spectrum
    implement equipment designed to operate on
    channel bandwidths of 12.5 kHz or less, or that
    meets a specific efficiency standard.

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Narrowbanding Defined
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800 MHz Band
  • 1987 Public Safety National Plan?
  • Allocated 800 MHz for public safety use.
  • Designated channels for mutual aid use.
  • Set trunking and system consolidation
    requirements.

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700 MHz Initiative
  • 700 MHz band is being reallocated from commercial
    TV to public safety.
  • 10 designated for nationwide interoperable
    communications.
  • Equipment developed for 700 MHz use must be
  • Non-proprietary.
  • Compatible with all current 800 MHz equipment.

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D Block Allocation
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Technology Issues and Concepts
  • Any Questions?

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