Transcript TETRA DMO - tetraforum.pl

The power of TETRA Direct Mode Operation
Francesco Pasquali
Selex Communications
Agenda
• Introduction to Direct Mode Operation (DMO)
• Applications & related benefits
• Services & facilities
• Conclusions
Why Direct Mode in Trunking?
Legacy trunking offered many benefits over conventional
communications and was a great success in the market
Automatic
Operation
Spectral
Efficiency
?
DMO
Ease of
Data
Services
Feature Rich
Service
BUT ...
It missed a key feature that conventional
communications offered:
direct communication outside network
coverage
TETRA offers the best of two worlds
TRUNKING MODE
DIRECT MODE
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
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
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
Back-to-back scenario (1/3)
TRUNKED
TETRA
For border or out of
coverage area
communications...
TETRA
DMO
Back-to-back scenario (2/3)
TRUNKED
TETRA
FAIL!!
TETRA
DMO
… for communications
within coverage at
times of capacity
limitations (e.g. major
incidents)
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)
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)
‘Back-to-back’ DMO channel usage
Master uses Timeslot 1 for voice/data TX
TETRA DMO
Air Interface
TDMA frame
1
2
3
4
A
1
B
RX
DMO
Master
2
TX
TX
RX
A B C
Speech Slots
3
Slave (& Idle) use Timeslot 3 for pre-emption
4
1
C
RX
2
3
4
1
2
3
4
P
RX
TX
DMO
Slave
TX
‘Frequency
Efficient’ mode
can use timeslots
2 and 4 for
another call
Pre-emption
request
P
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
TETRA DMO: Repeater
TETRA
DMO
Repeater
TETR
A
DMO
FAIL!!
Special radio terminal equipment called DMO repeater, allows
enlarging the DMO coverage when needed
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
• Dual carrier (1B) DM repeater
– 1 communications
– Two frequencies: DM1 for Rx & DM2 Tx
– Reduces potential RF interference to TMO
Preferred Frequency Usage
DM
Trunked Mode
Air Interface
BS RX
BS TX
Preferred Frequency Usage
DM1
DM2
Trunked Mode
Air Interface
BS RX
BS TX
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
Preferred Frequency Usage
DM2
DM1
Trunked Mode
Air Interface
BS RX
BS TX
Benefits of DM Repeater
• Same benefits as back-to-back DMO in terms of
Reliability
Cost
Special Applications
• BUT … on a wider area and with increased
communication reliability
TETRA DMO: Gateway
Special radio terminal
equipment can operate
as a gateway between
the two worlds
TRUNKED
TETRA
TETRA
DMO
TETRA
DMO Gateway
DM Gateway
Preferred Frequency Usage
TM2
TM1
• Enables DMO terminals to communicate
with the trunking system & vice versa
• Uses ‘normal’ DMO air interface
(single call)
DM1
Trunked Mode
Air Interface
BS TX
BS RX
Uplink (TM1)
Gateway
Downlink (TM2)
• One DMO
carrier per call
DMO User
Trunked Mode
Cell
Benefits of DM Gateway
• Reliability:
– 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
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
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
Benefits of Dual Watch
• Cost:
– 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
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
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 & 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)
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
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
Conclusions
• 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
The power of TETRA Direct Mode Operation
Thank you
Francesco Pasquali
OTE