1 Trunking 101 Radio Technology Presentation July 13, 2007 Rey Freeman, GeoComm.
-
Upload
esther-osborne -
Category
Documents
-
view
215 -
download
0
Transcript of 1 Trunking 101 Radio Technology Presentation July 13, 2007 Rey Freeman, GeoComm.
1
Trunking 101Trunking 101
Radio Technology Presentation
July 13, 2007
Rey Freeman, GeoComm
2
Presentation Agenda
Trunking Radio Systems “101”• Trunked radio vs. conventional radio systems
Simulcast transmitting technology Voting receiver system technology Digital vs. analog modulation technology
3
“Trunking 101”
CentralController
4
What is “Trunking” ?
It is NOT a term that “belongs” to Motorola, Ma/Com, or any other manufacturer
It is NOT a term exclusively for radio systems It IS a generic term used to describe:
“The sharing of a limited number of communications paths (or Trunks) among Many Users”
5
Conventional vs. Trunked
Conventional Radio (repeater) system:• Uses a dedicated radio frequency for each
radio channel in a system (unless sharing a channel)
• A Channel = a Frequency (I.e., 154.235 Mhz is County Fire)
• Each frequency is assigned to a group of users
6
TX
RX
FD
Fire Channel
154.235 MhzTX
RX
EMS Channel
155.340
TX
RX
Law Repeater Channel 155.625 Mhz
EMS
PD
7
TX
RX
FD
Fire Channel
154.235 Mhz
TX
RX
EMS Channel
155.340
TX
RX
Law Repeater Channel 155.625 Mhz
EMS
PD1PD2
??
X
8
Your Bank Tellers – as “Conventional”
PD FireEMS PWAdmin
EMS FD
FDPD
PD
Queueby
Account
9
Conventional vs. Trunked
Conventional Radio (base or repeater) system:• A Channel = a Frequency • If a channel is in use, radio user must wait in
“queue” before being able to transmit on the system
• …and a new frequency must be obtained each time another “channel” is needed in the radio system
• The system is limited by the number of frequencies in the system…
10
Trunked Radio Systems
CentralController
11
Conventional vs. Trunked
Trunked Radio (repeater) system:• Uses a group of similar radio frequencies to
create a “pool” for radio system users to access• Systems can be built using VHF, UHF or 800
Mhz• A Channel is NOT a Frequency…(generally)• A Channel (on your radio) is now a computer-
generated code• …and are now referred to as “Talk Groups”
12
Conventional vs. Trunked
Trunked Radio (repeater) system:• The entire system is managed by a computer,
often referred to as the “Central Controller”• All radios in the system also are computer-
controlled, and communicate to the central controller via one frequency known as the “Control Channel”
13
EMS
1 to 28 Channels
CH 1
CentralController
TX
RX
CH 2
RX
TX
CH 3
RX
TX
CH 4
RX
TX
CH 28
RX
TX
ControlChannel
PD
Basic Trunking Diagram
FD
14
Your Bank Tellers – as “Trunked”
Director CH 5CH 3 CH 4CH 2
EMS FD
PD
PD
Queueby
FirstAvailable
Teller
FD
IN
15
Conventional vs. Trunked
Trunked Radio Benefits: • Greatly improved usage of scarce radio
frequencies• Greater overall radio system flexibility,
including:Channel (Talk Group) capabilitiesVarious user features, including Emergency
Alarm, PTT ID, Channel Regrouping, Call Alert, and Radio Inhibit
• Brings radio users together on a common radio system
• Consistency in radio coverage
16
So How Does It Work?
17
Control Channel continuously transmits system data to all radios PD
CH 1
CentralController
TX
RX
CH 2
RX
TX
CH 3
RX
TX
CH 4
RX
TX
CH 28
RX
TX
ControlChannel
FDEMS
18
Radio user presses TX button, and radio information is sent via control channel to
Central Controller
CH 1
CentralController
TX
RX
CH 2
RX
TX
CH 3
RX
TX
CH 4
RX
TX
CH 28
RX
TX
ControlChannel
FD
19
Central Controller processes inbound request, and sends repeater channel command (CH 3) back to all radios
selected on same Talk Group
CH 1
CentralController
TX
RX
CH 2
RX
TX
CH 3
RX
TX
CH 4
RX
TX
CH 28
RX
TX
ControlChannel
FD
FD
20
Originating radio user’s radio automatically switches to correct voice channel and begins transmitting; All radios selected on same Talk Group do the same and hear the
voice transmission
CH 1
CentralController
TX
RX
CH 2
RX
TX
CH 3
RX
TX
CH 4
RX
TX
CH 28
RX
TX
ControlChannel
FD
FD
21
When transmission is completed, all units revert back to Control Channel
CH 1
CentralController
TX
RX
CH 2
RX
TX
CH 3
RX
TX
CH 4
RX
TX
CH 28
RX
TX
ControlChannel
FD
FD
22
Radio System Fleetmapping:
Radio “channels” are now called “Talk Groups”
(Law Enforcement shown here)
1 Itasca Co Law 1 IT Law 1 Y Y 1 22 Itasca Co Law 2 IT Law 2 Y Y 2 23 Itasca Co Law 3 IT Law 3 Y Y 1 34 Itasca Co Law Tac IT Law Tac Y Y? 2 35 Itasca Co SO Admin IT SO Adm Y N 1 36 Itasca Co Srch & Res IT S-R Y N 2 37 Itasca Co Probation IT Prob Y N 1 38 Itasca Co SO Jail IT SO Jail N ? n/a n/a9 Grand Rapids PD GR PD Ops Y Y 2 210 Drug Task Force IT DTF Y N11 Emer. Response Team IT ERT Y N
12 Law Scene of Action SOA P1 N N n/a n/a
13 Grand Rapids PD Admin GR PD Adm Y N 1 414 Bigfork Police Admin BF PD Adm Y N 2 415 Bovey Police Admin BV PD Adm Y N 1 416 Coleraine Police Admin CL PD Adm Y N 2 417 Deer River Police Admin DR PD Adm Y N 1 418 Keewatin Police Admin KW PD Adm Y N 2 419 Nashwauk Police Admin NW PD Adm Y N 1 4
Talk
gro
up
Nam
e
Talk
gro
up
Ali
as
(AB
BR
)
Tru
nked
?
Dis
patc
h?
Fail
so
ft
Ch
an
nel
Talk
gro
up
Pri
ori
ty
23
Fire & EMS Talk Groups
Talk
gro
up
Nam
e
Talk
gro
up
Ali
as
(AB
BR
)
Tru
nked
?
Dis
patc
h?
Fail
so
ft
Ch
an
nel
Talk
gro
up
Pri
ori
ty
Itasca Co Fire 1 IT Fire 1 Y Y 3 2Itasca Co Fire 2 IT Fire 2 Y Y 4 2Itasca Co Fire 3 IT Fire 3 Y Y 3 3
Itasca Co Fire Tac IT Fire Tac Y Y 4 4
Fire/EMS Scene of Action SOAFIRE1 N N n/a n/a
Balsam Fire Admin BS FD Adm Y N 3 4Bigfork Fire Admin BF FD Adm Y N 4 4Bovey Fire Admin BV FD Adm Y N 3 4
Calumet Fire Admin CA FD Adm Y N 3 4Cohasset Fire Admin CH FD Adm Y N 4 4Coleraine Fire Admin CL FD Adm Y N 3 4Deer River Fire Admin DR FD Adm Y N 4 4Goodland Fire Admin GL FD Adm Y N 3 4
Grand Rapids Fire Admin GR FD Adm Y N 4 4Keewatin Fire Admin KW FD Adm Y N 3 4Marble Fire Admin MB FD Adm Y N 4 4
Nashwauk Fire Admin NW FD Adm Y N 3 4Squaw Lake Fire Admin SQ FD Adm Y N 4 4
Taconite Fire Admin TC FD Adm Y N 3 4Warba/Feely/Sago Fire Admin WFS FD Adm Y N 4 4
Fire VHF Mu Aid FD Muaid Y Y 3 3Itasca Co EMS 1 IT EMS (AMB) 1 Y Y 5 2Itasca Co EMS 2 IT EMS (AMB) 2 Y Y 6 2
Itasca Co EMS Tac IT EMS (AMB) Tac Y Y 3
Fire/EMS Scene of Action SOAFIRE2 N N n/a n/a
Bigfork Ambulance Admin BF AMB Adm Y N 5Buck Lake 1st Responders BL 1st AdmDeer River Ambulance Admin DR AMB Adm Y N 6
Meds1 Ambulance Admin M1 AMB Adm Y N 5Naswauk Ambulance Admin NW AMB Adm
Squaw Lake 1st Resp Admin SQ 1st Adm Y N 6
24
Questions…so far?
25
Simulcast Transmitting Systems
Simulcast Transmitting is defined as: • A radio system where the same radio
frequencies are Simultaneously Broadcast from all tower sites within the radio system
• This allows same radio frequencies to be used throughout the entire coverage area
26
Simulcast Transmitting Systems
Simulcast Benefits:• Seamless communications throughout the radio
system’s coverage area• Improved radio frequency utilization• Improved coverage in areas with difficult
terrain• Improved in-building coverage (signals in
overlap zones are “additive”)
27
Simulcast Transmitting Systems
Simulcast “cons”: • Not inexpensive technology• Tower site spacing is critical (especially when
using NPSPAC frequencies)• Signal “timing” is critical between all sites• Tower site interconnection (microwave, T1,
etc.) is also critical and can be expensive
28
Simulcast Transmitting Systems
Site 1Site 2
Site 3
f1 f2 f3 f4 f5
f1 f2 f3 f4 f5
f1 f2 f3 f4 f5
29
f1 f2 f3 f4 f5
f1 f2 f3 f4 f5
Kandiyohi Co MN – with Simulcast
30
31
““Simulcast” fills in where single site can’tSimulcast” fills in where single site can’t
32
Simulcast Issues
• Amplitude and frequency of transmitted signals must be very accurately timed to ensure good signal quality
33
Simulcast Issues
• Slightly out of phase - “Ghosting” on a T.V. set
• Out-of-phase signals can cause destructive cancellation
• Fully in-phase signals produce constructive composite signal
34
Discussion and questions regarding Simulcast transmission
techniques and issues?
35
Multicast Transmitting Systems
Multicast Transmitting is defined as: • A radio system where different radio
frequencies are used at each tower site within the radio system
Multicast Benefits:• Reduced system complexity• Minimized site spacing issues• Lower system overall system cost
36
Multicast Transmitting Systems
Multicast “cons”: • Very high frequency usage (each site needs its
own set of frequencies)• No Simulcast coverage benefits (overlap,
voting)• Units “roam” between sites
37
f1 f2 f3 f4 f5
f6 f7 f8 f9 f10
Kandiyohi Co MN – with Multicast
38
ARMER System
In the ARMER system, each tower site is connected back to Zone Controller via microwave or other network link
Typical ARMER tower site is Multicast Typical Local Ehancement system is
Simulcast
39
Zone Controller
40
Radio System Modulation Technologies
• Analog vs. Digital:Most existing Public Safety radio
systems are analogNew 800 Mhz system are digitalSo what’s the difference? Is digital better, and why?
41
Modulation Techniques
Analog transmission
Digital transmission
Information is sent by changing the frequency, amplitude or phase of the radio signal
Information is converted to true data bits, and applied directly to the radio transmitter using FDMA, (or TDMA or CDMA)
42
Modulation Techniques
• Digital Benefits: Clearer audio throughout system coverage
area
Improved radio frequency efficiency
Improved system coverage
Imbedded signaling options
Encryption with no range loss
43
Voting Receiver Technology
In a multi-tower site radio system, a mobile or portable radio transmitting within the system’s range has a good probability of being heard by more than one tower site
In a Voting receiver system, the same-frequency receivers of the trunked repeater stations are connected together back to a main site…
…where – in a digital system – all received signals from one “channel” are combined (added) together and used to create a the final received product…
…which may be stronger than the original signal!
44
Voting Receiver Systems
Site 1
Site 2
Site 3
f1 f2 f3 f4 f5
f1 f2 f3 f4 f5f1 f2 f3 f4 f5
Comparator
Received audio to System
45
Discussion&
Questions