The power of TETRA Direct Mode Operation

Andrea Festelli

OTE

Agenda

•

Introduction & explanation of Direct Mode Operation (DMO)

•

Services & facilities

•

Benefits & Applications

•

Conclusions

Why Direct Mode in Trunking?

Legacy trunking offered many benefits over conventional communications and was a great success in the market

Spectral Efficiency Ease of Data Services Automatic Operation Feature Rich Service

BUT ...

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.

TRUNKING MODE DIRECT MODE

What is TETRA Direct Mode ? There are 4 basic operational modes of TETRA DMO:

1

“Back-to-back”

( standard DMO terminal coverage) 2

DMO Repeater

( extended DMO terminal coverage) 3

Dual Watch

( periodic “scanning” of ‘other’ mode) 4

DMO Gateway

(relay between DMO and TMO)

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

TRUNKED TETRA For border or out of coverage area communications...

TETRA DMO

FAIL!!

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

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

TETRA DMO: Repeater

TETRA DMO Repeater TETR A DMO FAIL!!

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

TETRA DMO: Dual watch

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

TETRA DMO: Gateway

Special radio terminal equipment can operate as a gateway between the two worlds TRUNKED TETRA TETRA DMO TETRA DMO Gateway

TETRA operation modes

TETRA provides 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

As shown for “back-to-back”, also other DMO modes can be useful under the trunked network coverage

‘Back-to-back’ DMO

Timeslot 1 is used by the Master The Slave uses Timeslot 3 TETRA DMO Air Interface TDMA frame

A

2 4

B

2 4

C

2

P

4 2 RX RX RX TX 4 DMO Master TX TX RX

A B C

Speech Slots TX ‘Frequency Efficient’ mode can use timeslots 2 and 4 for another call Pre-emption request

P

DMO Slave

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)

DM1 TYPE 1A • Single carrier (1A)

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

MS RX MS TX TYPE 1B • Dual carrier (1B)

– 1 conversation, 2 DM channels – Reduces potential for RF interference

DM1 DM2 MS RX MS TX

DMO Repeater type 1A

DMO Master

Speech Slots

A B

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

TDMA frame

Slave

A

2 numbering 3 2 4 3

A

4

B

2 3 2 3

B

4 4 2 1

P

2 3 4 1 4 2 1 2 3

P

4 4

TETRA DMO A.I.

Carrier X 1 TETRA DMO Repeater 1A

A B P

DMO Slave

Pre-emption request

P

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

DMO Repeater Type 2

• •

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

DM1 TYPE 2 DM2 RPT RX RPT TX

DMO Repeater type 2

2 B channel can use timeslot 2 and 4 4 2 4 2

A P

4 TETRA DMO Repeater 2

P A

Downlink Carrier Timeslot 1 is still used by the Master, the Slave still uses Timeslot 3 Uplink Carrier

A

2 2

P

4 4 2 4

A

Speech Slots

DMO Master

P

Pre-emption request

DMO Slave

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

•

Enables DMO terminals to communicate with the trunking system & vice versa Frequency Usage DM1 TM1 TM2 Trunked Mode Air Interface GW RX GW TX

•

Uses ‘normal’ DMO air interface (single call) Uplink (TM1) Gateway Downlink (TM2)

•

One DMO carrier per call DMO User Trunked Mode Cell

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

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

O.K.

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

DMO

• …. generated by modified DMO Gateway device • Validity time encoded in authorising signal

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