Interoperable Emergency Communications Training INTEROP03 Radio Operations Unit 1

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Interoperable Emergency Communications
TrainingINTEROP03Radio OperationsUnit 1
Technology Issues and Concepts

• STATE OF ALASKADivision of EnterpriseTechnology
  Services

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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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