tetra - direct mode operation
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TETRA - Direct Mode Operation. Doug Gray Motorola. AGENDA. Introduction & explanation of Direct Mode Operation (DMO) Services & Facilities Benefits & Applications Conclusions. DMO. WHY DIRECT MODE IN TRUNKING?. - PowerPoint PPT PresentationTRANSCRIPT
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TETRA - Direct Mode Operation
Doug GrayMotorola
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AGENDA
• Introduction & explanation of Direct Mode
Operation (DMO)
• Services & Facilities
• Benefits & Applications
• Conclusions
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WHY DIRECT MODE IN TRUNKING?
SpectralSpectralEfficiencyEfficiency
Automatic Automatic OperationOperation
Feature Rich Feature Rich ServiceService
Ease of Ease of Data ServicesData Services
• Trunking offered many benefits over conventional communications and was a great success in the market
?• It missed a key feature that conventional communications offered - direct communication outside network coverage
• TETRA’s multi-mode capability offers the best of both worlds - Trunking and Direct Communications in a single terminal.
DMO
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WHAT IS TETRA DIRECT MODE ? • There are 4 basic operational modes of TETRA DMO, viz.
1 “Back-to-back”“Back-to-back” (standard DMO terminal coverage)
2 DMO RepeaterDMO Repeater (extended DMO terminal coverage)
3 Dual Watch Dual Watch (periodic “scanning” of ‘other’ mode)
4 DMO GatewayDMO Gateway (continuous relay between modes)
• Communication between Direct Mode terminals• Communication between trunked and DMO terminals
• Further permutations are possible, e.g. Gateway/Repeater
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TRUNKEDTRUNKEDTETRATETRA
A1A1
A3A3A2A2
B1B1
B2B2
B3B3
TETRATETRADMODMO
CCTETRATETRADMODMO
TETRA DMO - BACK-TO-BACK
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TRUNKEDTRUNKEDTETRATETRA
A1A1
A3A3
A2A2
B1B1
B2B2
B3B3TETRATETRADMODMO
CC
TETRATETRADMODMODMO RepeaterDMO Repeater
DMO RepeaterDMO Repeater
TETRA DMO REPEATER
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TRUNKEDTRUNKEDTETRATETRA
B1B1
B2B2
B3B3
TETRATETRADMODMO
CC
A1A1
A3A3A2A2
TETRATETRADMODMO
Dual-WatchDual-Watch
Dual-WatchDual-Watch
TETRA DMO-DUAL WATCH
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TETRA DMO - GATEWAY
TRUNKEDTRUNKEDTETRATETRA
B1B1
B3B3
TETRATETRADMODMO
CC
A1A1
A3A3
TETRATETRADMODMO
GatewayGateway
GatewayGateway
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‘BACK-TO-BACK’ DMO
DMOMaster
DMOSlave
1 2 3 4
Slot Structure
Speech Slot
Pre-emption
1 2 3 4DMO Air Interface ‘Frequency Efficient’
mode can use these timeslots for another call
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DMO CHARACTERISTICS
• Normal DMO enables 1 conversation per carrier(i.e. 1 per 4 timeslots)
• Transmitting radio acts as ‘Master’ on a single timeslot
• Receiving radio is ‘Slave’ on a single timeslot• In normal mode, two time slots are used, two are
free• In Frequency Efficient Mode, all four timeslots are
used (2x2) enabling two conversations per carrier
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DMO REPEATER TYPE 1A & 1B• Only one call per repeater • Uses a 4 slot structure
•2 slot uplink •2 slot downlink•Master/slave operation (3 slot delay)
• Single carrier (1A)•Simple RF•1 conversation, 1 DM channel•Single carrier
MS RX
DM1
MS TX
TYPE 1A
• Dual carrier (1B) •More complex RF•1 conversation, 2 DM channels•Supports multiple repeaters•Reduces potential for RF interference
MS RX
DM1
MS TX
TYPE 1B
DM2
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DMO REPEATER TYPE 1A
Type 1A Repeater
DM1
Frequency Usage
MS RX
Direct ModeChannelDM1
SPEECH DOWNSLOT
Direct Mode
Channel
DM1DMOMaster
SPEECH UPSLOT
1 2 3 4 1 2 3 4
1 2 3 4 1 2 3 4
Master Slot
1 2 3 4
Slave Slot
DMO Air Interface
DMOSlave
Pre-EmptionUpslot
(Slave slot pattern moved for diagram clarity)
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• Two simultaneous calls per repeater
• Uses a 4 slot structure•4 slot uplink
•4 slot downlink
•Master/slave operation (4 slot delay)
• Dual carrier•More complex RF but supports multiple repeaters
• Uses power control and addressing
DMO REPEATER TYPE 2
RPT RX
DM1
RPT TX
TYPE 2
DM2
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DMOMaster
SPEECH UPSLOT
DMOSlave
Direct Mode
Channel
DM1
SPEECH DOWNSLOT
Direct ModeChannelDM2
Type 2 Repeater
1 2 3 4 1 2 3 4
Uplink Carrier
1 2 3 4
Downlink Carrier
1 2 3 4 1 2 3 4
DMO Air Interface
DMO REPEATER TYPE 2
‘B’ channel can use other slots
Pre-EmptionUpslot
(Slave slot pattern omitted for diagram clarity)
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DUAL WATCH
• Radio is operational in one system mode (Direct or Trunked) and simultaneously monitors signalling on the other system.
Mobile Unit whilst engaged in a call in Trunking mode
is alerted of a DMO call/request from a DMO terminal.
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DMO GATEWAY• Enables DMO terminal
to communicate with the trunking system & vice versa
• Uses ‘normal’ DMO air interface(single call)
Gateway
Direct M
ode
Channel
DM1
DMO User
Uplink (TM1)
Downlink (TM2)
'Normal' DMO AirInterface
(One simultaneous call)
Trunked ModeCell
Trunked ModeAir Interface
GW RX
DM1
GW TX
TM1 TM2
Frequency Usage
• One DMO carrier per call
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DMO REPEATER/GATEWAY
• Combines the functionality of a repeater and a
gateway (similar to a VHF-UHF talk-through
repeater)
• Interconnects direct mode to trunked mode
• Uses ‘normal’ DMO air interface
(single call)
• Can be manned or stand alone (i.e. free running
or manned by an operator)
Trunked ModeAir Interface
GW RX
DM1
GW TX
TM1 TM2
Frequency Usage
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BENEFITS of DMO GATEWAY
• Extends range of Trunking Mode Operation
• Reduces Infrastructure costs
• Enables remote ‘occasional users’ to have
communication at cost effective rates
• Gives Network Operators better coverage
possibilities during early stages of network roll-
out
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MANAGED DIRECT MODE - MDMO
• Generated by authorising device which is in permanent contact with system, or…..
• …. generated by modified DMO Gateway or Repeater/Gateway device
• Validity time encoded in authorising signal
• MDMO terminal is restricted from transmitting unlessit receives an authorising signal O.K.
DMO
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BENEFITS OF MDMO
• Network Operators maintain better control of
their network resource/ revenues
• Removes potential for interference
• Manages roaming
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DMO SERVICES AND FACILITIES• Simplex speech - Individual or Group Call• Circuit mode data up to 7.2 kbps, incl. point-to-point & point-to-multipoint
• Status and short data service (SDS)• Late Entry• Emergency call• Talking Party Identification (TPI) , incl. concealment
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DMO SECURITY (ENCRYPTION)
• Air-interface encryption - TEA1, TEA2 &
TEA3, incl. time stamping• Implicit authentication• Key management incl. Over The Air Rekeying
(OTAR)• “Zapping” (enabling/ disabling) terminals• End-to-end encryption mechanism
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DMO BENEFITS & APPLICATIONS
• Operation outside the coverage of Trunking
Infrastructure• Gives extra capacity when trunked network is highly
loaded• Operations in poor signal strength areas• Fall-back operation when the Trunking Infrastructure
system is inoperative• Covert Operations - cannot be monitored by Contol• ‘Stripline’ applications (power, oil, water distribution
lines) not requiring trunked network capacity
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CONCLUSIONS
• TETRA is a multi-mode standard offering trunking and
conventional operation in-one
• DMO - a powerful feature in the total TETRA offering, as
it comprises of several sub-modes of operation
• Significant commonality with trunked V+D TETRA
enables for multi-mode terminals (DMO & V+D)
• DMO is a significant differentiator between TETRA and
other cellular services
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TETRA - Direct Mode Operation
Thank You
Doug GrayMotorola