The power of TETRA - Direct

Mode Operation

Andrea FestelliOTE

Agenda

• Introduction & explanation of Direct Mode Operation (DMO)

• Services & facilities

• Benefits & Applications

• Conclusions

Why Direct Mode in Trunking?

SpectralSpectralEfficiencyEfficiency

Automatic Automatic OperationOperation

Feature RichFeature RichServiceService

Ease of Ease of Data Data ServicesServices

Legacy 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 in a single terminal.

DMO

TRUNKING MODE

BUT ...

DIRECT MODE

What is TETRA Direct Mode ?

There are 4 basic operational modes of TETRA DMO:

1 “Back-to-back”“Back-to-back” (standard DMO terminal coverage)

2 DMO RepeaterDMO Repeater (extended DMO terminal coverage)

3 Dual WatchDual Watch (periodic “scanning” of ‘other’ mode)

4 DMO GatewayDMO Gateway (relay between DMO and TMO)

TETRA DMO: Back-to-back (1/2)

TETRATETRADMODMO

For border or out of coverage area communications...

TRUNKEDTRUNKEDTETRATETRA

TETRA DMO: Back-to-back (2/2)

TETRATETRADMODMO

… and to provide communications within coverage at times of capacity limitations

TRUNKEDTRUNKEDTETRATETRA

FAIL!!

TETRA DMO: Repeater

Special radio terminal equipment called DMO repeater, allows enlarging the DMO coverage when needed

FAIL!!

TETRATETRADMODMO

RepeaterRepeaterTETRTETR

AADMODMO

TETRATETRADMODMO

TETRA DMO: Dual watchSpecial radio terminal equipment can simultaneously get in touch with both TMO and DMO worlds

TRUNKEDTRUNKEDTETRATETRA

TETRATETRADual WatchDual Watch

TerminalTerminal

TETRA DMO: Gateway

TETRATETRADMODMO

Special radio terminal equipment can operate as a gateway between the two worlds

TRUNKEDTRUNKEDTETRATETRA

TETRATETRADMO GatewayDMO Gateway

TETRA operation modes

DMO adds border or out of coverage area communications

TETRA provides integrated digital trunked (TMO) and direct (DMO) modes of operation

DMO provides communications within coverage at times of capacity limitationsAs shown for “back-to-back”, also other DMO modes can be useful under the trunked network coverage

‘Back-to-back’ DMO

‘Frequency Efficient’ mode

can use timeslots 2 and 4 for

another callSpeech Slots

A B C

DMOMaster

TX TX TXDMOSlave

RX RXRX

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 request

P

TX

RX

P

Timeslot 1 is used by the Master

11 1 1

The Slave uses Timeslot 3

33 3 3

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

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)– 1 conversation, 1 DM channel– Single carrier– Higher spectrum efficiency

MS RX

DM1

MS TX

TYPE 1A

• Dual carrier (1B) – 1 conversation, 2 DM channels– Reduces potential for RF interference

MS RX

DM1

MS TX

TYPE 1B

DM2

DMO Repeater type 1A

Pre-emption request

P

The Master still uses its Timeslot 1 and Timeslot 3 as in back-to-back

TETRA DMO TETRA DMO Repeater Repeater 1A1A

DMO Master

DMO Slave

TETRA DMO A.I. Carrier X

Master numbering

Slave numbering

BA P

Speech Slots A B

TDMA frame

1 2 3 4

2 3 4 1

1 2 3 4

2 3 4 1

1 2 3 4

2 3 4 1

1 2 3 4

12 3 4A B PA B P

The Slave still uses its

Timeslot 1 and Timeslot 3 as

in back-to-back

1

11

1

3

3

• 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

DMO Repeater Type 2

RPT RX

DM1

RPT TX

TYPE 2

DM2

DMO Repeater type 2

Pre-emption requestP

Timeslot 1 is still used by the Master, the Slave still uses

Timeslot 3

TETRA DMO TETRA DMO Repeater Repeater 22

DMO Master DMO Slave

Uplink Carrier

A

P

Speech SlotsA

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

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

CarrierA

1 1 1

1 1 1

P

3 33

3 33

PB channel can use

timeslot 2 and 4

Dual Watch• Radio is operational in one system mode (Direct or

Trunked) and simultaneously monitors signalling on the other system.

Mobile Unit whilst idle (Idle Dual Watch) or engaged in a call (Full Dual Watch) in Direct mode

is alerted of a TMO call/request from a TMO terminal.

DMO Gateway

• Uses ‘normal’ DMO air interface(single call)

Gateway

Direct Mode

Channel

DM1

DMO User

Uplink (TM1)

Downlink (TM2)

Trunked ModeCell

Trunked ModeAir Interface

GW RX

DM1

GW TX

TM1 TM2

Frequency Usage

• One DMO carrier per call

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

Benefits of DMO Gateway

• Extends range of Trunking Mode Operation (e.g.

radio cell fringes, tunnels, buildings, …)

• 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

Managed Direct Mode - MDMO

• Generated by authorising device which is in permanent contact with system, or…..

• …. generated by modified DMO Gateway device

• Validity time encoded in authorising signal

• MDMO terminal is restricted from transmitting unlessit receives an authorising signal

O.K.DMO

Benefits of MDMO

• Network Operators maintain better control of

their network resource/ revenues

• Removes potential for interference

• Manages roaming

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.

suppression

DMO Security (Encryption)

• Air-interface encryption - TEA1, TEA2, TEA3 and TEA4 incl. time stamping

• Implicit authentication

• End-to-end encryption mechanism

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

Control• ‘Stripline’ applications (power, oil, water

distribution lines) not requiring trunked network capacity

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