The power of TETRA Direct Mode Operation

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The power of TETRA - Direct Mode Operation

• Francesco Pasquali
• Selex Communications

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Agenda

• Introduction to Direct Mode Operation (DMO)
• Applications related benefits
• Services facilities
• Conclusions

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Why Direct Mode in Trunking?
BUT ...
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What PMR users ask?

• Users require to communicate everywhere at
  anytime, regardless of
• lack of network coverage
• lack of resources
• any type of network failure

• and always need
• emergency communications
• security
• voice data transmission, individual group
  calls

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TETRA operation modes
TETRA terminals provide integrated digital
trunked (TMO) and direct (DMO) modes of operation
DMO adds border or out of coverage area
communications
DMO provides communications within coverage at
times of capacity limitations or whenever
connection with the infrastructure is not needed
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What is TETRA Direct Mode ?

• There are 4 basic operational modes of TETRA DMO
• Back-to-back
• standard terminal to terminal communications
• DM Repeater
• extension of DMO terminal coverage
• DM Gateway
• relay between DMO and TMO
• Dual Watch
• periodic scanning of other mode

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Back-to-back scenario (1/3)
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Back-to-back scenario (2/3)
for communications within coverage at times of
capacity limitations (e.g. major incidents)
TETRA DMO
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Back-to-back scenario (3/3)
for communications within coverage if
connection to the infrastructure is not needed or
wanted (localised activities or private
communications)
Direct communication
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DMO Characteristics

• Normal mode DMO enables 1 communication per
  carrier (i.e. 1 per 4 timeslots, 2 slots used 2
  free)
• Frequency Efficient Mode DMO enables 2
  communications per carrier (i.e. all 4 slots
  used, 2 slots used per each call)
• Transmitting radio acts as Master on a single
  DMO channel (i.e. pair of alternated time slots)
• Receiving radio is Slave on a single DMO
  channel
• Timeslot 1 is used as traffic channel for voice
  and data transmission by the Master radio
• Timeslot 3 is used for signalling transmission by
  Master, slave and idle radios (e.g. for
  pre-emption and PTT request)

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Back-to-back DMO channel usage
Master uses Timeslot 1 for voice/data TX
Slave ( Idle) use Timeslot 3 for pre-emption
A
B
C
P
Frequency Efficient mode can use timeslots 2
and 4 for another call
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Benefits of Back-to-back DMO

• Reliability
• Local area communications always granted under
  any kind of fault of the network (disruption,
  congestion, interference)
• Cost
• Relaxed requirements for coverage in low-traffic
  areas and enclosed areas (e.g. buildings,
  tunnels, underground areas, etc.)
• Relaxed requirements for base station channels
  provisioning
• Special Applications
• Local area operations (e.g. strip-line)
• Covert operations

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TETRA DMO Repeater
Special radio terminal equipment called DMO
repeater, allows enlarging the DMO coverage when
needed
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DM Repeater Type 1A 1B

• Based on usual 4 slot structure
• 2 slots for Master ? Repeater transmissions
• 2 slots for Slave / Idle ? Repeater transmissions
• Master/slave operation (3 slot delay)

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DM Repeater Type 2

• Two simultaneous calls per repeater

• Based on usual 4 slot structure
• Two alternated slots per call on each link
• Master/slave operation (4 slot delay)

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Benefits of DM Repeater

• Same benefits as back-to-back DMO in terms of

Reliability
Cost Special Applications

• BUT

on a wider area and with increased communication
reliability
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TETRA DMO Gateway
Special radio terminal equipment can operate as a
gateway between the two worlds
TRUNKED TETRA
TETRA DMO
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DM Gateway

• Enables DMO terminals to communicate with the
  trunking system vice versa

• Uses normal DMO air interface (single call)

• One DMO carrier per call

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Benefits of DM Gateway

• Reliability
• Trunked communications through adjacent cells
  partially supported under fault of one radio base
  station
• Cost
• More relaxed requirements for coverage in
  low-traffic areas and enclosed areas (incl.
  buildings, tunnels, underground areas, etc.)
• Better coverage possibilities during early stages
  of network roll-out
• Special Applications
• Enable occasional and immediate coverage at
  cost-effective rates

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TETRA DMO Dual watch
Special radio terminal equipment can get in touch
with both TMO and DMO worlds simultaneously
TRUNKED TETRA
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Dual Watch

• The Radio is operational in one mode (Direct or
  Trunked) and simultaneously monitors the other
  for incoming communications.

• In particular the Radio Unit whilst idle (Idle
  Dual Watch) or engaged in a call (Full Dual
  Watch) in Direct mode
• receives TMO call, status and short messages
  from TMO users

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Benefits of Dual Watch

• Cost
• Enlarge communication support in fringe areas it
  allows further relaxing of coverage requirements
• Special Applications
• Improve local area communications terminals
  avoiding to waste resources can be contacted
  whenever needed

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Managed Direct Mode - MDMO

• MDMO terminal is restricted from transmitting
  unless it receives an authorising signal

• Authorisation can be received
• directly from the SwMI (for Dual Mode or Dual
  Watch terminals)
• from a DMO gateway and/or repeater device
• from an authorising device permanently in contact
  with the system

• Authorisation can be limited both in time and
  geographically

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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 Group Call
• Late Entry
• Transmitting Party Identification (TPI), incl.
  suppression
• Emergency pre-emptive calls
• Status and Short Data Service (SDS)
• Circuit mode data up to 7.2 kbps (P2P and P2MP)

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DMO Security (Encryption)

• Air-interface encryption
• Static Key Encryption
• TEA1, TEA2, TEA3 and TEA4 incl. time stamping
• Implicit authentication
• Provided by Air Interface Encryption
• End-to-end encryption

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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 (allows
  more relaxed coverage requirements and lower the
  related expenditure)
• Fall-back operation when the Trunking
  Infrastructure system is inoperative
• Covert Operations - cannot be monitored by
  Control
• 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 direct communication in-one
• DMO - a powerful feature thanks to exhaustive set
  of sub-modes of operation
• Significant commonality with trunked VD TETRA
  enables for dual-mode terminals actually
  available on the market

DMO is a key differentiator between TETRA and
other, public and private, cellular technologies
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The power of TETRA - Direct Mode Operation
Thank you

• Francesco Pasquali
• OTE