1. The power of TETRA - Direct Mode Operation
Francesco Pasquali
Selex Communications

2. Agenda Introduction to Direct Mode Operation (DMO)
Applications & related benefits
Services & facilities
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 offers the best of two worlds
DMO ?
It missed a key feature that conventional communications offered:
direct communication outside network coverage
TRUNKING MODE
DIRECT MODE

4. 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

5. TETRA operation modes
TETRA terminals provide 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 or whenever connection with the infrastructure is not needed

6. 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

7. Back-to-back scenario (1/3)
TRUNKED
TETRA
TETRA
DMO
For border or out of coverage area communications...

8. Back-to-back scenario (2/3)
TRUNKED
TETRA
… for communications within coverage at times of capacity limitations (e.g. major incidents)
FAIL!!
TETRA
DMO

9. Back-to-back scenario (3/3)
… for communications within coverage if connection to the infrastructure is not needed or wanted (localised activities or private communications)
communication
Direct

10. 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)

11. ‘Back-to-back’ DMO channel usage
Master uses Timeslot 1 for voice/data TX
Slave (& Idle) use Timeslot 3 for pre-emption
TETRA DMO Air Interface TDMA frame 1 2 3 4 1 3 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. 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
xxx

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

14. DM Repeater Type 1A & 1B Based on usual 4 slot structure
2 slots for Master  Repeater transmissions
2 slots for Slave / Idle  Repeater transmissions
Master/slave operation (3 slot delay)
Single carrier (1A) DM repeater
1 communications
Single frequency DM for Tx & Rx
Higher spectrum efficiency
Trunked Mode
Air Interface
BS RX DM
BS TX
Preferred Frequency Usage
Dual carrier (1B) DM repeater
1 communications
Two frequencies: DM1 for Rx & DM2 Tx
Reduces potential RF interference to TMO
Trunked Mode
Air Interface
BS RX
DM2
BS TX
Preferred Frequency Usage
DM1

15. DM Repeater Type 2 Two simultaneous calls per repeater
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: DM1 for Rx & DM2 Tx
Need for RF full duplex Hw platform
More complex and expensive than Type 1
Trunked Mode
Air Interface
BS RX
DM1
BS TX
Preferred Frequency Usage
DM2

16. Benefits of DM Repeater
Same benefits as back-to-back DMO in terms of
Reliability
Cost
Special Applications
xxx
on a wider area and with increased
communication reliability
BUT …

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

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

19. Benefits of DM Gateway Reliability: Cost: Special Applications:
Trunked communications through adjacent cells partially supported under fault of one radio base station
Cost:
More relaxed 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
Special Applications:
Enable “occasional and immediate coverage” at cost-effective rates

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

21. 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) in Direct mode
receives TMO call, status and short messages from TMO users

22. Benefits of Dual Watch Cost: Special Applications:
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

23. Managed Direct Mode - MDMO
MDMO terminal is restricted from transmitting unless it receives an authorising signal
O.K.
DMO
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
Authorisation can be limited both in time and geographically

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

25. 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)

26. 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

27. 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

28. Conclusions DMO is a key differentiator between TETRA and
TETRA is a multi-mode standard offering trunking and direct communication in-one
DMO - a powerful feature thanks to exhaustive set of sub-modes of 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

29. The power of TETRA - Direct Mode Operation
Thank you
Francesco Pasquali
OTE