1. Angelo Benvenuto Leonardo Finmeccanica.
DMO - TETRA Direct Mode
Angelo Benvenuto
Leonardo Finmeccanica.

2. Agenda DMO Modes, Services and facilities
DMO and the key differences with TMO
Equipment types :
Repeaters
Gateways
Operational example
Benefit and Applications
Conclusion

3. What PMR users ask? Fast Reliable Secure lack of network coverage
Regardless of
lack of network coverage
lack of resources
any type of network failure

4. TETRA operation modes TETRA standard provides 2 Operation Modes
Direct Mode Operation (DMO)
Trunked Mode Operation (TMO)
DMO doesn’t require an infrastructure
TMO requires a well deployed network infrastructure
DMO adds border or out of coverage areas communications
TMO provides a wide set of features
DMO provides a well defined subset of TMO features

5. Protocol details DMO protocol stack TMO protocol stack DMO
Frame structure

6. There are 4 basic operational modes of TETRA DMO:
DMO operational modes
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

7. DMO Characteristics Normal mode
Frequency Efficient mode DMO enables 2 communications per carrier (i.e. all 4 slots used, 2 slots used per each call)

8. TETRA DMO: Repeater
Special radio terminal equipment called DMO repeater widen the DMO coverage when needed reaching an MS out of the coverage
Based on usual 4 slot structure
there are different type of Repeater:
DM Repeater 1A For Normal Mode
DM Repeater 1B For Normal Mode
DM Repeater 2 For Freq Efficient Mode (Obsolete)

9. DM Repeater Type 1A & 1B Single carrier (1A) DM repeater
1 communications
Single frequency DM for Repeater Tx & Rx
Higher spectrum efficiency
Trunked Mode
Air Interface
MS RX DM
MS TX
Type 1A
Dual carrier (1B) DM repeater
1 communications
Two different frequencies: DM1 for Rx & DM2 for Tx
Reduces potential RF interference
Trunked Mode
Air Interface
RP RX
DM2
RP TX
Type 1B
DM1

10. TETRA Gateway
Special radio terminal equipment can operate as a gateway between the two worlds

11. DM Gateway
Trunked Mode
Air Interface
GW RX
DM1
GW TX
TM1
TM2
Frequency Usage
Enables DMO terminals to communicate with the trunking system & vice versa
Gateway uses the ‘normal’ Back2Back DMO mode (single call)
One DMO carrier per call

12. Benefits of DM Gateway Reliability:
Trunked communications through adjacent cells partially supported under fault of one radio base station
Cost:
less strict 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

13. Type summary DMO type channels calls Back to back 1
Back to back – Frequency efficient 2
Repeater Type 1A
Repeater Type 1B
Repeater Type 2
Gateway
Type 1A Repeater / Gateway
Type 1B Repeater / Gateway

14. Key differences between DMO/TMO (1/2)
Individual call (point-to-point)
Group call (point-to-multipoint)
Circuit mode data transfer
Short data service (type 1, 2, 3, 4)
Status messages
Late entry
Emergency and pre-emptive calls
OTAR (over the air re-keying) 
4 slots
(up to 28.8 kbit/s)
 (Simplex) 
1 slot
(up to 7.2 kbit/s)

15. Key differences between DMO/TMO (2/2)
Air interface encryption
End to end encryption
IP packet data
Call authorized by dispatcher
Ambience listening
Network based features
Call forwarding
Call recording   
 (gateway)

16. Operational Example: An Emergency outside the Network Coverage
Needs of a fast network deployment
Simple and Fast
Wide Coverage Area

17. DMO Benefits & Applications
Operations outside the coverage of Trunking Infrastructure
Covert Operations – cannot be monitored by Control
Strip-line applications (power, oil and water distribution lines) not requiring trunked network capacity
Operations in poor signal strength areas (allows more relaxed coverage requirements and lower the related expenditure)
Backup operation when the Trunking Infrastructure system is inoperative

18. Conclusions
TETRA is a multi-mode standard offering trunking & direct communication in-one
DMO - a powerful feature thanks to its wide set of sub-modes of operation
DMO is a key differentiator between TETRA and other, public and private, cellular technologies

19. Thank you