radio 101 for esf #2

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Radio 101 for ESF #2Webinar Presentation for ESF #2

2pm EST, Monday, February 28, 2011Ross Merlin

DHS Office of Emergency Communications

2/28/2011

The author is a senior telecommunications specialist with the DHS Office of Emergency Communications. His Federal emergency communications experience includes disaster response with the National Disaster Medical System, FEMA wireless management, DHS spectrum management, and now the OEC Technical Assistance branch. He is the author of the National Interoperability Field Operations Guide (NIFOG). You may contact him via email: [email protected] .

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Public Safety Radio Bands

• VHF-Low Band: 30 MHz to 50 MHz• VHF-High: 138 MHz to 174 MHz• UHF: 406 MHz to 512 MHz• 700 MHz (new)• 800 MHz• 4.9 GHz (new)

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Can we talk?

• Most radios only operate in one band!– Multi-band radios are rare and expensive

• If Agency A uses VHF and Agency B uses UHF, they can’t talk to each other unless they:– Use runners– Have face-to-face interoperability – co-locate at

Command Post– Swap radios– Relay through dispatchers– Connect through a gateway

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Propagation & Band Characteristics• VHF Low Band (30-50 MHz)

– Best propagation in undeveloped and hilly terrain– Poor building penetration

• VHF High Band (150.8-174 MHz)– Very good propagation in undeveloped and hilly terrain– Moderate building penetration

• UHF (450-470; some areas 421-430 or 470-512 MHz; Federal Government 406.1-420 MHz)– Good propagation in undeveloped and hilly terrain– Good building penetration

• 700/800 MHz– Poor propagation in undeveloped and hilly terrain– Very good building penetration

• 4.9 GHz– Microwave propagation used for short range (WiFi type) or point-to-point

links2/28/2011

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Frequencies vs. Channels

• A frequency is a point in the radio spectrum– Part of what describes a channel

• A channel is a set of parameters that can include one or more frequencies, Continuous Tone Coded Squelch System (CTCSS) tones, bandwidth, modulation, name, etc.

• Example: VCALL10 is a channel with transmit and receive frequency 155.7525 MHz, transmit CTCSS tone of 156.7 Hz, no receive CTCSS tone, bandwidth 11.25 kHz

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Continuous Tone Coded Squelch System (CTCSS) Tones

• PL stands for Private Line, a Motorola trademark• Other names include Code Guard, Tone Squelch,

Call Guard, Channel Guard, Quiet Channel, Privacy Code, Sub-audible Tone, etc.

• Generic (vendor-neutral) term is CTCSS – Continuous Tone Coded Squelch System

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What Are CTCSS Tones Used For?

• CTCSS tones are used to MASK interference• They DO NOT remove interference• Useful for masking interference caused by

computers, electronics, etc.• Useful for masking interference from “skip”• Should NOT be used to block out traffic from

neighboring (nearby) departments– This is OK for taxis, etc., but not for public safety– Creates “Hidden Interference” problem – missed calls

possible

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Radio Programming

• Programming a radio is not like programming a microwave oven

• Oven: Universal programming tool (fingertip) works with all brands. Graphic User Interface (touchpad) similar

• Radio: Every brand has their own tools: cables, adapters, software. No standard for frequency (MHz or kHz), CTCSS (frequency or code), Network Access Code (NAC) (hex or decimal), etc.

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Results of Improper CTCSS Programming

• If Radio 1 is set for transmit (TX) tone only and Radio 2 is set for transmit/receive (TX/RX), both radios will hear each other. Radio 1 will hear any interference on the channel

• If Radio 1 is set for TX tone only and Radio 2 is set for no tone, both radios will hear each other. Both radios will hear any interference on the channel

• If Radio 1 is set for TX/RX tone and Radio 2 is set for TX/RX tone, both radios will hear each other.

• If Radio 1 is set for TX/RX tone and Radio 2 is set for no tone, Radio 1 will not hear Radio 2. Radio 2 will hear Radio 1

• ANY radio programmed with an incorrect TX tone will not be heard by radios using a RX tone, even though it can hear traffic from other radios

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Results of Improper Frequency Programming

• You can hear other stations but can’t be heard• You can’t hear other stations but they can hear you• You can’t hear other stations or be heard• You can hear other stations when they are close to you,

but can’t hear them when they are far away (via a repeater)

• You are transmitting on an unauthorized frequency, causing interference to a different radio system

• You are listening to a different radio system but think it is yours – you are very confused

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Simplex

• Very Reliable• Limited Range• Radio Channel uses 1 frequency

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Duplex• Radio Channel using 2 frequencies: Frequency 1 to talk

from radio A to radio B, and Frequency 2 to talk from radio B to radio A

• Each user must be line of sight with each other• Examples: Cordless Telephone systems, which both

parties can talk at the same time and listen at the same time.

f1

f2

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Base Station – Height Improves Range

Unit 1

Dispatch CenterUnit 2

Unit 3

Unit 4

Some units don’t hear transmission because of obstructions

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Base Station – Height Improves Range

Unit 1

Dispatch CenterUnit 2

Unit 3

Unit 4

Dispatcher relays message – heard by all units

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Remote Base Operation

Unit 1

Unit 2Unit 3

Unit 4

Dispatch CenterRemote Link

Microwave, Phone Line, etc.

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Conventional Repeater

• Receives a signal on one frequency and retransmits (repeats) it on another frequency

• Placed at a high location• Increases range of portable and mobile radio

communications• Allows communication around obstructions (hills,

valleys, etc.)• User radios receive on the repeaters transmit

frequency and transmit on the repeater’s receive frequency

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f1

f2 f2f2

f2f1

RX TX

Conventional RepeaterAll units within range of repeater hear all transmissions through the repeater

Unit 1

Unit 2

Unit 3

Unit 4

Dispatch Center

f2

Repeater2/28/2011

PD 2

PD 1

PD 3

PD 4

FD 1

FD 2

FD 3

PW 1

PW 2PW 3

Conventional SystemsWhen one user is talking, other users on that channel cannot talk, even though other repeaters in the area may be idle.

Communicating

Idle

IdlePD 3 cannot talk to PD 4 because PD 1 is using the repeater

Public works repeater may be idle 90% of the time, which means that frequency is largely wasted

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Trunking

• Trunking is a method of combining repeaters at the same site (often multiple sites) to “share” frequencies among users

• Spectrally efficient• Allows many more “virtual” channels (called

talkgroups) than there actually are frequencies authorized to the system

• Computer controlled

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f1

f2f2

f2f1RX TX

Trunked System

f4f3RX TX

f6f5RX TX

PD 1

PD 2

Shared Repeater Bank

PD 3

FD 1

FD 2

f3

f4

• Frequencies are dynamically assigned by system controller

• User radio may be on a different frequency every time it transmits

• Talkgroups are “virtual” channels• Possible to have many more

talkgroups than actual frequencies

• Statistically, not all talkgroups will be active at the same time

System Controller

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Trunked System Operation• User radios continuously monitor a dedicated “control channel”• When a user wants to transmit, the user’s radio makes a request to

the system controller• If a repeater is available, the system controller temporarily assigns

that repeater channel to the talkgroup making the request• Transmitting user’s radio will give a “talk beep”, indicating that a

repeater has successfully been assigned…then the user can talk• All user radios monitoring that talkgroup automatically switch to

the frequency of the assigned repeater and hear the transmission• When the transmission is complete, all radios return to monitoring

the control channel

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Multi-Site Systems

• Conventional– Repeaters on same output, different input– Linked repeaters on different frequencies– Remote Receive Sites

• Voting

– Simulcasting• Trunking

– Roaming– Simulcasting

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Repeaters on same output frequency, different input frequency (or CTCSS tone)

Users must manually change channel to different repeater depending on their physical location

Only one repeater active at a time

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Repeaters on same output frequency, different input frequency (or CTCSS tone)


Only one repeater active at a time

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Linked repeaters on different frequencies


Link (microwave, phone line, etc.)

Both repeaters active at the same time with same traffic, but on different frequencies

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Voting Receivers

Users do not need to change channel depending on location. System (voter) automatically picks best receive tower site.


RX Only Site

Voter

Central Transmitter

Voter (comparator) chooses best received signal and sends that signal to the transmitter

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Simulcasting

Transmitters must be carefully synchronized to prevent interference in overlap areas

Both repeaters transmit on the same frequency at the same time


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Caller: “The radio system is down.”You: “What kind of system?”

VHF UHF 700 800Analog Conventional Simplex

Conventional Repeater*

Trunking Repeater very rare

rare for PS

Digital Conventional Simplex Conventional Repeater Trunking Repeater

* Single site? Voted receive sites? Linked repeaters? Simulcast?

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Possible Points of Failure• User Radio

– Untrained user– Trying to use beyond coverage area, or shielded by terrain– Loss of power (base station) or dead battery (hand-held)

• Repeater– Loss of commercial power, backup battery or generator fuel

exhausted– Antenna failure (wind or ice damage)– Catastrophic site loss (tornado, fire, explosion)

• Link (T1 line, microwave link, etc.)– Loss of power– Antenna failure– Telco circuit outage (phone line, internet)

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Network Status

• In a telco or cellular telephone network there is a Network Operations Center (NOC) that knows the status of the network

• In Land Mobile Radio (LMR) there is no “the network”– Each radio system is independent– A statewide system or a trunked system may monitor the

status of some components of just that system– No one place to go to learn status of all LMR systems

• Commercial Mobile Radio Service (CMRS) networks may have a NOC; most public safety radio systems not CMRS customers, they are government-owned LMR

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Limitations of the Technology

• Radios, without infrastructure, have a short effective range – line-of-sight

• Repeaters extend range, but require power• Repeater systems and networks extend the

coverage area, but increase complexity• Trunked radio systems increase capacity, but are

much more complicated and are not easily transportable

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Regulatory & Operational Limitations

• Users can not program radios – must be done by a technician (FCC Part 90; not so for NTIA). Some agencies’ radios are password protected - if their technician is not a first responder (and won’t share the password) field programming not possible

• Rules are ambiguous and arcane; written for day-to-day operability and interoperability, not catastrophic disaster response

• All radio frequencies used by responders should be coordinated with Disaster Emergency Communications (DEC) Group Frequency Manager before use

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Programming Limitations

• Programming in the field, while under stress , is more likely to lead to errors

• Front-panel programming takes a lot of time• Programming by computer takes time to setup the first time,

then fast to program multiple radios with the same channels; model-specific hardware and software

• Cloning to program multiple radios is fast, but requires model-specific cloning cable and radio passwords

• Trunked radio system key needed to program radios, but seldom shared – system tech too busy to program key and freqs into visiting responders’ radios

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Problems You May Handle (1 of 3)

• Call from state/local (other than simple question) didn’t come through state ESF #2– Refer caller to state ESF #2

• Call about radio/telephone/Internet in Joint Field Office (JFO)– Transfer call to JFO Logistics Section, Comm. Unit

• Question about radio frequencies/channels– Transfer to your Spectrum Manager

(continued)

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• You didn’t deploy your Spectrum Manager?– Shame on you!– Spectrum Manager needs to be among the first boots on the

ground – once behind, can never catch up

• Fed/state/local or Private Voluntary Organizations (PVO)/Non-Governmental Organization (NGO) needs radios, needs help programming radios, needs help repairing/installing/acquiring antenna, needs temporary tower, needs WiFi, needs internet backhaul, satellite communications, repeaters, remote base stations, trunked radio system…– Get specifics, then task to DEC Group of ESF #2

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• Before you start taking calls, work out with DEC Group whether they want to handle generator issues at communications sites, or whether those calls go to ESF #12 (Energy)

• Offer to donate radios or comm-specific supplies, services, technicians– Track or transfer in accordance with JFO donations

policy• Broadcast station needs help (including generator)

– Refer call to your FCC liaison2/28/2011

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Making Friends

• If FEMA installs equipment or an entire radio system for the locals, can the locals keep it?

2/28/2011

No. Non-consumable items purchased with Stafford Act funds will be recovered, refurbished, and re-used on a future disaster; or disposed of through normal US Government excess property procedures

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Summary

• This radio stuff is complicated• Get the right information on the first call• FEMA can get it, whatever it is (if justifiable)• Spectrum Managers – don’t leave home without

one

2/28/2011

Some of the material in this presentation was adapted from http://www.nmems.org/Communications/RadioTrainingSlidesGeneric.ppt

http://www.nmems.org/Communications/RadioTrainingSlidesGeneric.ppt



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