1. The power of TETRA - Direct Mode Operation
Andrea Festelli
OTE

2. Introduction & explanation of Direct Mode Operation (DMO)
Agenda
Introduction & explanation of Direct Mode Operation (DMO)
Services & facilities
Benefits & Applications
Conclusions

3. 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
BUT ...
TETRA’s multi-mode capability offers the best of both worlds in a single terminal.
DMO ?
It missed a key feature that conventional communications offered:
direct communication outside network coverage
TRUNKING MODE
DIRECT MODE

4. 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)

5. TETRA DMO: Back-to-back (1/2)
TRUNKED
TETRA
TETRA
DMO
For border or out of coverage area communications...

6. TETRA DMO: Back-to-back (2/2)
TRUNKED
TETRA
TETRA
DMO
… and to provide communications within coverage at times of capacity limitations
FAIL!!

7. TETRA DMO: Repeater FAIL!!
Special radio terminal equipment called DMO repeater, allows enlarging the DMO coverage when needed

8. 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

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

10. 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

11. ‘Back-to-back’ DMO A B C P A B C P DMO Master DMO Slave RX RX RX TX TX
Timeslot 1 is used by the Master 1
The Slave uses Timeslot 3 3
TETRA DMO Air Interface TDMA frame 1 2 3 4 A B C P TX TX RX TX RX RX RX TX
DMO
Master
DMO
Slave
‘Frequency Efficient’ mode can use timeslots 2 and 4 for another call
Speech Slots A B C
Pre-emption request P

12. 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

13. DMO Repeater Type 1A & 1B Single carrier (1A) Dual carrier (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

14. DMO Repeater type 1A A B A A B B P P P A B P DMO Master DMO Slave
Speech Slots A B
The Master still uses its Timeslot 1 and Timeslot 3 as in back-to-back
Master numbering
TDMA frame 1 2 3 4 1 1 3
TETRA DMO A.I. Carrier X A A B B P P
Slave numbering 1 1 3
Pre-emption request P
TETRA DMO Repeater 1A
The Slave still uses its Timeslot 1 and Timeslot 3 as in back-to-back A B P
DMO Slave

15. 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
RPT RX
DM1
RPT TX
TYPE 2
DM2

16. DMO Repeater type 2 A P P A A P A P DMO Slave DMO Master1 2 3 4 1 3
B channel can use timeslot 2 and 4
Downlink Carrier A P
Timeslot 1 is still used by the Master, the Slave still uses
Timeslot 3 P
TETRA DMO Repeater 2 A
Uplink Carrier A 1 2 3 4 P 1 3
DMO Slave
DMO Master
Speech Slots A
Pre-emption request P

17. 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.

18. Trunked Mode
Air Interface
GW RX
DM1
GW TX
TM1
TM2
Frequency Usage
DMO Gateway
Enables DMO terminals to communicate with the trunking system & vice versa
Uses ‘normal’ DMO air interface (single call)
Uplink (TM1)
DMO User
Gateway
Downlink (TM2)
Direct Mode
Channel
DM1
One DMO carrier per call
Trunked Mode
Cell

19. 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

20. Managed Direct Mode - MDMO
MDMO terminal is restricted from transmitting unless it receives an authorising signal
O.K.
DMO
Generated by authorising device which is in permanent contact with system, or…..
…. generated by modified DMO Gateway device
Validity time encoded in authorising signal

21. Benefits of MDMO
Network Operators maintain better control of their network resource/ revenues
Removes potential for interference
Manages roaming

22. 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

23. DMO Security (Encryption)
Air-interface encryption - TEA1, TEA2, TEA3 and TEA4 incl. time stamping
Implicit authentication
End-to-end encryption mechanism

24. 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

25. 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