Land Mobile Radio Systems
Content
National Communications System (NCS) ESF #2 Training Conference
LAND MOBILE RADIO SYSTEMS AND HOW TO RESTORE THEM
Major Curtis Bowers
Plaquemines Parish Sheriff¶s Office [email protected] 504-392-1652 June 21, 2007
Class Topics
Types of Radio Systems
Simplex Trunking APCO Project 25
Frequencies Getting a system back online Radio gateway devices
Different Types of Radio Systems
Conventional Systems Simplex Operation (Radio-to-Radio) Repeater
Trunking Systems Single Site Multicast Simulcast Conventional Digital
Conventional Systems
Simplex Operation Transmissions are made over the same frequency Transmissions are from radio to radio ± no system infrastructure needed
Conventional Systems
Carrier Squelch - open to interference Private Line Code ± keeps radio signals on same frequency from keying into radio or opening the carrier squelch Interference audio is still present
Conventional Systems
What are the advantages of this type of system? Cost ± almost any radio will work, as long as frequency is correct Small number of users Small coverage area No infrastructure is needed
Conventional Repeater Systems
Repeaters boost transmission power for greater range Antennas are placed on towers for increase in coverage area
400¶
5 watts
100 watts
25 watts
Conventional Repeater Systems
Repeater systems improve portable and mobile talk-out and talk-in coverage A duplex system uses two frequencies. The radio transmits audio into the repeater and repeater sends out the audio at a higher wattage on a different frequency Antenna on a tower with a repeater gives a greater range Antenna on a tower with a pre-amp receive system increases talk-in coverage
Trunking Systems
Trunking systems consist of several repeaters controlled by computerized system System manages users, talkgroups, and repeaters
Repeaters
Control Channel
Central Controller
Trunking Systems
Trunking systems can be a single site or consist of multiple sites over large regions Each repeater has its own frequency and one of these repeaters is a control channel Control channel manages information to and from the user¶s radios With this information, channels (repeaters) are assigned to users for radio traffic Control channel is always communicating with affiliated radios Affiliated radios send talkgroup (TG) info to system
Trunking Systems Voice Channel Request
PTT Request
1 4 3
Control Channel
2
Central Controller
Trunking Systems
There can be numerous talkgroups and users on this type of system Capacity is determined by number of channels (repeaters) the system has There can be numerous sites (towers) used on this type of system Size of system is limited to the number of frequencies the owner can obtain, the manufacture of the system, the version of system in service, and how much the owner can afford
Trunking Systems
Different types of multi-site systems:
Multicast: The multiple broadcast of identical audio information on different frequencies from multiple, geographically separated sites Simulcast: The simultaneous broadcast of identical audio information on the same frequency from multiple, geographically separated sites
Trunking Systems Multicast System Example
Site 1 1 2
CC VC
Site 2 3 4 5
CC VC VC
Site 3 6 7 8
CC VC VC
Trunking Systems
Site 1
Site 2
1 2 3
CC VC VC
4 5 6
CC VC VC
Site 3
Multicast cells could be combinations of sites in what is also called a Simulcast configuration
7 8
CC VC
Trunking Systems Simulcast System Example
Site 1 1 2 3 4 5 6 7 8
CC VC VC VC VC VCVC VC
Site 2 1 2 3 4 5 6 7 8
CC VCVC VC VC VCVC VC
1 2 3 4 5 6 7 8
CC VC VC VC VC VCVC VC
Site 3
Trunking Systems Simulcast ³Seamless´ Coverage
Site 1 Site 2
1 2 3 4 5 6 7 8
CC VC VC VC VC VC VC VC
2 1 2 3 4 5 6 7 8
CC VC VC VC VC VC VC VC
1 2 3 4 5 6 7 8
CC VC VC VC VC VC VC VC
Site 3
Trunking Systems
Trunking systems with multiple sites have a weak link in their operation; links must go back to the master site Links can be T-1 circuits or microwave links Multicast sites that lose their links go into site trunking and no longer communicate with other sites In a simulcast system, only the prime site will continue to operate; all other remote simulcast sites are off line until links are reestablished A simulcast cell can also go into site trunking
Trunking Systems
Analog operation Mix mode consisting of digital and analog resources APCO 25 systems digital only Digital is not a secure communication system, encryption is for secure communication
Analog vs. Digital
Benefits of Digital Technologies Improved Audio Quality
Good
Digital
Audio Quality
Analog
Poor Strong Signal Strength Weak
Frequency Issues
License for frequencies to be restored or used Special Temporary Authorization (STA¶s) obtained Equipment must match frequency range of system Service equipment, software, and hardware needed to tune equipment to frequencies to be restored Types of equipment needing tuning for frequencies: Combiners, duplexers, repeaters, tower top amp's, and radios
Restoring a Communication System
Survey what is left that still works or that can be put back in service What type of system will be initially put in service At tower sites you will need antennas, antenna mounts, antenna cable, cable connectors, tower climbing crew, and site master testing equipment
Restoring a Communication System
Determine how this equipment can be transported to the site If this is a remote site how will it be connected (linked) back to other sites: microwave, phone circuits, or broadband satellite Locate or identify a vendor or service shop that can perform many of these task for you
Restoring a Communication System
Installing a new communication system What does the supported agency need What type of technology will be used What is best for the agency being supported, not what the vendors want to sell
Radio Gateways
How will this device help Will it even work with the system or systems being connected Get permission before connecting systems together Set the rules for how this gateway channel or talkgroup will be used
Radio Gateways
When a problem arises with this connection, a contact person must be available 24 hrs a day Not always the best way to connect groups of users together
Questions
Any questions welcome
Contact Information
Major Curtis Bowers Plaquemines Parish Sheriff¶s Office 8344 Hwy 23 Belle Chasse, LA 70037 504-392-1652 office 504-812-9305 cell [email protected] www.ppso.net
LAND MOBILE RADIO SYSTEMS AND HOW TO RESTORE THEM
Major Curtis Bowers
Plaquemines Parish Sheriff¶s Office [email protected] 504-392-1652 June 21, 2007
Class Topics
Types of Radio Systems
Simplex Trunking APCO Project 25
Frequencies Getting a system back online Radio gateway devices
Different Types of Radio Systems
Conventional Systems Simplex Operation (Radio-to-Radio) Repeater
Trunking Systems Single Site Multicast Simulcast Conventional Digital
Conventional Systems
Simplex Operation Transmissions are made over the same frequency Transmissions are from radio to radio ± no system infrastructure needed
Conventional Systems
Carrier Squelch - open to interference Private Line Code ± keeps radio signals on same frequency from keying into radio or opening the carrier squelch Interference audio is still present
Conventional Systems
What are the advantages of this type of system? Cost ± almost any radio will work, as long as frequency is correct Small number of users Small coverage area No infrastructure is needed
Conventional Repeater Systems
Repeaters boost transmission power for greater range Antennas are placed on towers for increase in coverage area
400¶
5 watts
100 watts
25 watts
Conventional Repeater Systems
Repeater systems improve portable and mobile talk-out and talk-in coverage A duplex system uses two frequencies. The radio transmits audio into the repeater and repeater sends out the audio at a higher wattage on a different frequency Antenna on a tower with a repeater gives a greater range Antenna on a tower with a pre-amp receive system increases talk-in coverage
Trunking Systems
Trunking systems consist of several repeaters controlled by computerized system System manages users, talkgroups, and repeaters
Repeaters
Control Channel
Central Controller
Trunking Systems
Trunking systems can be a single site or consist of multiple sites over large regions Each repeater has its own frequency and one of these repeaters is a control channel Control channel manages information to and from the user¶s radios With this information, channels (repeaters) are assigned to users for radio traffic Control channel is always communicating with affiliated radios Affiliated radios send talkgroup (TG) info to system
Trunking Systems Voice Channel Request
PTT Request
1 4 3
Control Channel
2
Central Controller
Trunking Systems
There can be numerous talkgroups and users on this type of system Capacity is determined by number of channels (repeaters) the system has There can be numerous sites (towers) used on this type of system Size of system is limited to the number of frequencies the owner can obtain, the manufacture of the system, the version of system in service, and how much the owner can afford
Trunking Systems
Different types of multi-site systems:
Multicast: The multiple broadcast of identical audio information on different frequencies from multiple, geographically separated sites Simulcast: The simultaneous broadcast of identical audio information on the same frequency from multiple, geographically separated sites
Trunking Systems Multicast System Example
Site 1 1 2
CC VC
Site 2 3 4 5
CC VC VC
Site 3 6 7 8
CC VC VC
Trunking Systems
Site 1
Site 2
1 2 3
CC VC VC
4 5 6
CC VC VC
Site 3
Multicast cells could be combinations of sites in what is also called a Simulcast configuration
7 8
CC VC
Trunking Systems Simulcast System Example
Site 1 1 2 3 4 5 6 7 8
CC VC VC VC VC VCVC VC
Site 2 1 2 3 4 5 6 7 8
CC VCVC VC VC VCVC VC
1 2 3 4 5 6 7 8
CC VC VC VC VC VCVC VC
Site 3
Trunking Systems Simulcast ³Seamless´ Coverage
Site 1 Site 2
1 2 3 4 5 6 7 8
CC VC VC VC VC VC VC VC
2 1 2 3 4 5 6 7 8
CC VC VC VC VC VC VC VC
1 2 3 4 5 6 7 8
CC VC VC VC VC VC VC VC
Site 3
Trunking Systems
Trunking systems with multiple sites have a weak link in their operation; links must go back to the master site Links can be T-1 circuits or microwave links Multicast sites that lose their links go into site trunking and no longer communicate with other sites In a simulcast system, only the prime site will continue to operate; all other remote simulcast sites are off line until links are reestablished A simulcast cell can also go into site trunking
Trunking Systems
Analog operation Mix mode consisting of digital and analog resources APCO 25 systems digital only Digital is not a secure communication system, encryption is for secure communication
Analog vs. Digital
Benefits of Digital Technologies Improved Audio Quality
Good
Digital
Audio Quality
Analog
Poor Strong Signal Strength Weak
Frequency Issues
License for frequencies to be restored or used Special Temporary Authorization (STA¶s) obtained Equipment must match frequency range of system Service equipment, software, and hardware needed to tune equipment to frequencies to be restored Types of equipment needing tuning for frequencies: Combiners, duplexers, repeaters, tower top amp's, and radios
Restoring a Communication System
Survey what is left that still works or that can be put back in service What type of system will be initially put in service At tower sites you will need antennas, antenna mounts, antenna cable, cable connectors, tower climbing crew, and site master testing equipment
Restoring a Communication System
Determine how this equipment can be transported to the site If this is a remote site how will it be connected (linked) back to other sites: microwave, phone circuits, or broadband satellite Locate or identify a vendor or service shop that can perform many of these task for you
Restoring a Communication System
Installing a new communication system What does the supported agency need What type of technology will be used What is best for the agency being supported, not what the vendors want to sell
Radio Gateways
How will this device help Will it even work with the system or systems being connected Get permission before connecting systems together Set the rules for how this gateway channel or talkgroup will be used
Radio Gateways
When a problem arises with this connection, a contact person must be available 24 hrs a day Not always the best way to connect groups of users together
Questions
Any questions welcome
Contact Information
Major Curtis Bowers Plaquemines Parish Sheriff¶s Office 8344 Hwy 23 Belle Chasse, LA 70037 504-392-1652 office 504-812-9305 cell [email protected] www.ppso.net
