The Power of TETRA-Direct Mode Operation-Selex Communications Francesco Pasquali

8/10/2019 The Power of TETRA-Direct Mode Operation-Selex Communications Francesco Pasquali

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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?

Spectral

Efficiency

Automatic

Operation

Feature Rich

Service

Ease of

Data

Services

Legacy trunking offered many benefits over conventional

communications and was a great success in the market

?

It missed a key feature that conventionalcommunications offered:

direct communication outside network

coverage

TETRA offers the best of two worlds

DMO

TRUNKING MODE

BUT ...

DIRECT MODE


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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

DMO adds

border or out ofcoverage area

communications

TETRA term inals pro vide in tegrated dig i tal tru nked (TMO) and

direct (DMO) modes o f operat ion

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)

TETRA

DMO

For border or out of

coverage area

communications...

TRUNKED

TETRA


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TETRADMO

for communications

within coverage at

times of capacity

limitations (e.g. major

incidents)

TRUNKEDTETRA

FAIL!!


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for communications within

coverage if connection to the

infrastructure is not needed

or wanted (localised activities

or private communications)


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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

Frequency

Efficient mode

can use timeslots

2 and 4 for

another callSpeech Slots

A B C

DMO

MasterTX TX TX

DMO

Slave

RXRX RX

TETRA DMO

Air Interface

TDMA frame

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

A B C

Pre-emption

requestP

TX

RX

P

Master uses Timeslot 1for voice/data TX

11 1 1

Slave (& Idle) useTimeslot 3 for pre-emption

33 3 3


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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

FAIL!!

TETRA

DMO

RepeaterTETR

A

DMO


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DM Repeater Type 1A & 1B

Based on usual 4 slot structure

2 slots for MasterRepeater transmissions

2 slots for Slave / IdleRepeater transmissions

Master/slave operation (3 slot delay)

Single carrier (1A) DM repeater

1 communications

Single frequencyDMfor Tx & Rx

Higher spectrum efficiency

Trunked Mode

Air InterfaceBS RX

DM

BS TX

Preferred Frequency Usage

Dual carrier (1B) DM repeater

1 communications

Two frequencies: DM1for Rx & DM2Tx

Reduces potential RF interference to TMO

Trunked Mode

Air Interface

BS RX

DM2

BS TX


DM1


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Two simultaneous calls per repeater

DM Repeater Type 2

Based on usual 4 slot structure

Two alternated slots per call on each link

Master/slave operation (4 slot delay)

Dual carrier

2 communications

2 frequencies: DM1for Rx &DM2Tx

Need for RF full duplex Hw platform

More complex and expensive than Type 1

Trunked Mode

Air Interface

BS RX

DM1

BS TX


DM2


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Benefits of DM Repeater Same benefits as back-to-back DMO in terms of

BUT on a wider area and with increased

communication reliability

Reliability

Cost

Special Applications


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TETRA DMO: Gateway

TETRA

DMO

Special radio terminal

equipment can operate

as a gateway between

the two worlds

TRUNKED

TETRA

TETRA

DMO Gateway


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DM Gateway

Uses normal DMO air interface

(single call)

Trunked Mode

Air Interface

BS RX

DM1

BS TX

TM1 TM2


One DMO

carrier per call

Enables DMO terminals to communicate

with the trunking system & vice versa

Gateway

DMO User Trunked Mode

Cell

Uplink (TM1)

Downlink (TM2)


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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 relaxedrequirements 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

TETRA DMO: Dual watch

Special radio terminal

equipment can get in touch

with both TMO and DMO

worlds simultaneously

TRUNKED

TETRA

TETRA

Dual Watch

Terminal


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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) inDirectmode

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

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

MDMO terminal is restricted

from transmitting unless it

receives an authorising signal

O.K.

DMO

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-modesof operation

Significant commonality with trunked V+D 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

Francesco Pasquali

OTE

Thank you

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The Power of TETRA-Direct Mode Operation-Selex Communications Francesco Pasquali

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