The Power of TETRA Direct Mode DMO

1
The Power of TETRA Direct Mode (DMO)

• Dr Richard Dewey
• Director TCI Limited
• Chairman ETSI project TETRA
• ad hoc working group on DMO

2
Outline of talk

• TCI capabilities - Trunked radio DMO
• Why do we need Direct Mode?
• How does TETRA Direct Mode overcome deficiencies
  of conventional back-to-back operation?
• Services supported by DMO
• Operational scenarios
• Summary

3
TCI capability - expert consultancy for all
stages in procuring and running a TETRA radio
system
Requirements capture preliminary analysis
Availability Resilience
Coverage
Write ITT
In Service Care
Procurement Support
Acceptance
Operations Maintenance
Evaluate Tenders
Grade of Service
Oversee Installation
Capacity Management Billing
Negotiate Contract
4
Why do we need DM operation?

• Mobile to mobile communication without
  infrastructure
• poor trunked mode coverage
• e.g. in-building, car parks, tunnels
• covert operation - invisible to infrastructure
• local overload - allows local comms without
  infrastructure
• fault conditions - fall back service if TMO
  inoperative
• Secondary coverage from vehicle to handheld
  terminal.

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Deficiencies of conventionalback-to-back
operation

• Not possible to record conversations.
• Promotes unstructured communications and
  unco-ordinated operations since command structure
  can not intervene.
• Leads to fragmented communications because there
  is no connection between back-to-back mobiles and
  main scheme mobiles.

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TETRA DMO overcomesmany of these deficiencies

• Gateway listening on DM operations allow
  recordings to be made.
• Gateway listening on DM operations allows remote
  priority intervention.
• Dual watch capability allows direct mode and
  trunked mode mobiles to contact each other.

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Tele Services Bearer Services Supported by
TETRA DMO
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TETRA DMO Tele Services

• Clear Speech or Encrypted Speech
• INDIVIDUAL CALL (POINT TO POINT) - Simplex only
• GROUP CALL (POINT TO MULTIPOINT)
• BROADCAST (POINT TO MULTIPOINT ONE WAY)
• DMO uses Static Cipher Key (SCK) - up to 32
  different
• End-to-end encryption can be provided

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TETRA DMO Bearer Services

• Single slot services only
• Circuit mode unprotected data 7.2 kbits/sec
• Circuit mode low protected data 4.8 kbits/sec
• Circuit mode high protected data 2.4 kbits/sec
• Short Data Services -
• 65535 Status messages (half reserved)
• user defined data types
• type 1-16 bits data
• type 2 -32 bits data
• type 3 - 64 bits data
• type 4 - up to 2047 bits data

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TETRA DMO PMR type Supplementary Services

• Pre-emptive priority.
• Late entry.
• Talking party ID.
• List search call.
• Call report

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Types of Direct Mode equipment

• DM-MS DM capable mobile station
• DM-REP Direct Mode REPeater
• DM-GATE Direct Mode GATEway
• DM-REP/GATE Direct Mode terminal with co-incident
  REPeater and GATEway functionality.

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Operational Scenarios
Gateway
DIRECT MODE GROUP
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Direct Mode MS-MS operation
Two separate talk groups each dual-watching the
other.
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Direct Mode repeater operation
Two separate talk groups one with DMO repeater,
other in trunked mode each dual-watching the
other.
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Direct Mode gateway operation
Single talk group throughout DMO/trunked coverage
areas. Mobiles in overlap can join either DMO or
trunked.
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Summary

• DMO is a powerful complementary service to
  trunked radio operation.
• Direct mode provides service in areas not served
  by the trunked infrastructure.
• Tetra DMO overcomes many of the deficiencies of
  traditional back-to-back.
• DMO is an essential part of most public service
  network capabilities.

Thanks for listening Dr Richard Dewey
44 1483 303268 www.tci-ltd.co.uk