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TETRA - Direct Mode Operation Doug Gray Motorola.

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Presentation on theme: "TETRA - Direct Mode Operation Doug Gray Motorola."— Presentation transcript:

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2 TETRA - Direct Mode Operation Doug Gray Motorola

3 AGENDA Introduction & explanation of Direct Mode Operation (DMO) Services & Facilities Benefits & Applications Conclusions

4 WHY DIRECT MODE IN TRUNKING? SpectralEfficiency Automatic Operation Feature Rich Service Ease of Data Services Trunking offered many benefits over conventional communications and was a great success in the market ? 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 - Trunking and Direct Communications in a single terminal. DMO

5 WHAT IS TETRA DIRECT MODE ? There are 4 basic operational modes of TETRA DMO, viz. “Back-to-back” 1 “Back-to-back” ( standard DMO terminal coverage) DMO Repeater 2 DMO Repeater ( extended DMO terminal coverage) Dual Watch 3 Dual Watch ( periodic “scanning” of ‘other’ mode) DMO Gateway 4 DMO Gateway (continuous relay between modes) Communication between Direct Mode terminals Communication between trunked and DMO terminals Further permutations are possible, e.g. Gateway/Repeater

6 TRUNKEDTETRA A1 A3 A2 B1 B2 B3 TETRADMO C TETRADMO TETRA DMO - BACK-TO-BACK

7 TRUNKEDTETRA A1 A3 A2 B1 B2 B3 TETRADMO C TETRADMO DMO Repeater TETRA DMO REPEATER

8 TRUNKEDTETRA B1 B2 B3 TETRADMO C A1 A3 A2 TETRADMO Dual-Watch Dual-Watch TETRA DMO-DUAL WATCH

9 TETRA DMO - GATEWAY TRUNKEDTETRA B1 B3 TETRADMO C A1 A3 TETRADMO Gateway Gateway

10 ‘BACK-TO-BACK’ DMO DMO Master DMO Slave 1234 Slot Structure Speech Slot Pre-emption 1234 DMO Air Interface ‘Frequency Efficient’ mode can use these timeslots for another call

11 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

12 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) Single carrier (1A) Simple RF 1 conversation, 1 DM channel Single carrier MS RX DM1 MS TX TYPE 1A Dual carrier (1B) More complex RF 1 conversation, 2 DM channels Supports multiple repeaters Reduces potential for RF interference MS RX DM1 MS TX TYPE 1B DM2

13 DMO REPEATER TYPE 1A Type 1A Repeater DM1 Frequency Usage MS RX Direct Mode Channel DM1 SPEECH DOWNSLOT Direct Mode Channel DM1 DMO Master SPEECH UPSLOT 1234 1234 12341234 Master Slot 1234 Slave Slot DMO Air Interface DMO Slave Pre-Emption Upslot (Slave slot pattern moved for diagram clarity)

14 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 Uses power control and addressing DMO REPEATER TYPE 2 RPT RX DM1 RPT TX TYPE 2 DM2

15 DMO Master SPEECH UPSLOT DMO Slave Direct Mode Channel DM1 SPEECH DOWNSLOT Direct Mode Channel DM2 Type 2 Repeater 1234 1234 Uplink Carrier 1234 Downlink Carrier 12341234 DMO Air Interface DMO REPEATER TYPE 2 ‘B’ channel can use other slots Pre-Emption Upslot (Slave slot pattern omitted for diagram clarity)

16 DUAL WATCH Radio is operational in one system mode (Direct or Trunked) and simultaneously monitors signalling on the other system. Mobile Unit whilst engaged in a call in Trunking mode is alerted of a DMO call/request from a DMO terminal.

17 DMO GATEWAY Enables DMO terminal to communicate with the trunking system & vice versa Uses ‘normal’ DMO air interface (single call) Gateway Direct Mode Channel DM1 Uplink (TM1) Downlink (TM2) 'Normal' DMO Air Interface (One simultaneous call) Trunked Mode Cell Trunked Mode Air Interface GW RX DM1 GW TX TM1TM2 Frequency Usage One DMO carrier per call

18 DMO REPEATER/GATEWAY Combines the functionality of a repeater and a gateway (similar to a VHF-UHF talk- through repeater) Interconnects direct mode to trunked mode Uses ‘normal’ DMO air interface (single call) Can be manned or stand alone (i.e. free running or manned by an operator) Trunked Mode Air Interface GW RX DM1 GW TX TM1TM2 Frequency Usage

19 BENEFITS of DMO GATEWAY Extends range of Trunking Mode Operation 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 Generated by authorising device which is in permanent contact with system, or….. …. generated by modified DMO Gateway or Repeater/Gateway device Validity time encoded in authorising signal MDMO terminal is restricted from transmitting unless it receives an authorising signal O.K. DMO

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. concealment

23 DMO SECURITY (ENCRYPTION) Air-interface encryption - TEA1, TEA2 & TEA3, incl. time stamping Implicit authentication Key management incl. Over The Air Rekeying (OTAR) “Zapping” (enabling/ disabling) terminals 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 Contol ‘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

26 TETRA - Direct Mode Operation Thank You Doug Gray Motorola


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