DMR Protocol Introduction

1. DMR Protocol Introduction Prepared by: Samuel Chia Date: 08-Apr-2009

2. Content • Introduction • Benefits of DMR Protocol • System Configuration • Channel Structure • Modulation • Operational scenarios • Burst Format • Protocol specs • Possible improvements

3. Declining Indirect market business. Create new business to churn analog based systems. Mandate by FCC that non frequency efficient (>= 12.5kHz equipment) will not be approved after 2005 due to congestion. However we now know that it has been postponed to 2011. And all Public safety equipment has to be migrated by 2013. IntroductionWhy DMR was pursued?

4. 2001 – Evaluation of DIIS (intended ETSI DMR protocol). 2002 – Draft a new 4FSK TDMA protocol (F2) for APCO P25 and DMR. Goal is to use for both products. 2003 – Protocol Prototyping start. 2004 – Start Product Development. – Start F2 protocol standardization with ETSI (Goal: Define the air interface. Define minimum set of voice and data features) 2005 – F2 Approved by ETSI and included in DMR First Version 2007 – First DMR Product Ship Accepted IntroductionProtocol Development History

5. Benefits of DMR Protocol • Spectrum efficiency via TDMA • 2X users, capacity and throughput • Allows 2 simultaneous calls through 1 repeater • Improved basic capabilities • Range improvement • Increased audio quality – ”Noise Cancellation and Digital Voice” • Improved battery life (Improve from 8 hours to 12 hours) • Enhanced Features (Test Messaging and Better Call handling) Slot 1 Slot 2

6. time Spectrum Efficiency via TDMA Slot 1 Slot 2 Slot 1 Slot 2 Regulatory emissions mask Slot 1 Slot 2 Slot 1 6.25kHz Sub- Channel 6.25kHz Sub- Channel frequency 12.5kHz Channel 12.5kHz Channel 12.5kHz Channel • 12.5kHz FDMA • Today, Analog • 1 voice for each 12.5kHz channel • 1 repeater for each channel • 12.5kHz TDMA • Divides existing channel into two timeslots • Delivers twice the capacity through the repeater • Performance is same or better than 12.5kHz FDMA • 1 repeater does work of 2; also reduces combining equipment • ETSI Tier 2 Standard for licensed bands • Enables 40% increase in radio battery life • 6.25kHz FDMA • Could squeeze into 12.5kHz channels but with reduced power. • Performance degraded • reduced range • more interference • Need 1 repeater for each sub-channel; cannot combine repeaters to share antenna site • ETSI Tier 1 Standard for licensed bands

7. Improved Digital Audio Quality and Range Excellent • - Clearer voice over a greater range • Digital error-correction technology permits audio and digital communications with no loss • - Improved range • Improved audio above min acceptable quality provide better range performance. • - Static and noise rejection • Digital receivers reject any error signals, permitting improved audio in loud environments Digital audio Audio quality Analog audio Improved audio Minimal acceptable audio Poor Strong Signal strength Weak

8. Increased Audio Quality • AMBE++ is a proven vocoder to have significant improved audio quality compared to Analog 25kHz channel. For a 12.5kHz channel, the MOS would be expected to be lower. • Noise Suppression technology is built into the vocoder which will improve audio quality in noisy environment. This gives significantly better background noise immunity compared to analog systems which has limited noise suppression capability. MOS – Mean Opinion Score

9. Improved Battery Life • 5/5/90 Duty Cycle • TDMA Tx is 30ms ON and 30ms OFF. This means that Tx current is about half of what it is in FDMA • 40% Battery Life Improvement with TDMA

10. One-to-Many Enables communication with specific sets of group members One-to-All Allows all on the same channel to hear communications Enhanced Features – Digital Calling and Signaling One-to-One Call and talk privately with a specific user’s radio NOTE: This also applies to Text Messaging where a user can type a message and send to the intended recipients.

11. f1 Up-link Down-link Up-link Down-link f1 f1 f1 f1 System Configurations Direct Mode Configuration Repeater Mode Configuration To other systems To PSTN/Intranet/Internet

12. System Configurations • DMR uses a 2:1 TDMA protocol, allows more conventional system configurations than a FDMA protocol. The following modes being used:- • 12.5e repeater mode - Slot 1 use for voice, Slot 2 use for data • 6.25e repeater mode - Both slot 1 & 2 use for voice or data (Slot 1 user cannot use Slo2 and vice versa) • 12.5kHz direct mode – Only one slot is being used. One call per 12.5kHz bandwidth. • (There are future intended operations which I will discuss in later slides)

13. Slot 1 Freq. 2 Slot 1 Freq. 1 Slot 2 Freq. 1 Slot 2 Freq. 2 Repeater Channel Structure (Repeater) • Example of 2 simultaneous voice call on one repeater • Outbound signaling is labeled “BS Tx” and inbound signaling is labeled “MS Tx”. • As shown figure the outbound channel contain a CACH (Common Announcement Channel)

14. Subscriber 2 Subscriber 1 Slot 1 Freq 1 Slot 1 Freq 1 LC LC Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Hdr Hdr Time Channel Structure (Direct Mode) • Example of 1 subscriber calling another in direct mode

15. Modulation • 4FSK Modulation for 12.5 kHz Channel Bandwidth • Modulation Type: 4 FSK, 4 level Frequency Shift Keying • Bit Rate: 9600 bits/second • Deviation index h=0.27 • Symbol 01 = 1.944 kHz • Symbol 00 = 0.648 kHz • Symbol 10 = - 0.648 kHz • Symbol 11 = -1.944 kHz

16. 30ms Slot Boundary Slot Boundary +4 dBc +1 dBc Ts1 0 dBc Te1 -1 dBc - 3 dBc Te Ts Slot center 1.25ms 6 symbol period -57 dBm -60 dBc 0 Watts (1.5ms) 1.5ms 27.5ms, Td (132 valid data symbols) Antenna Switch turned off here TTR Timing signal from OptA_Sel3 Antenna Switch turned on here Ramp down starts Modulation (Power Profile)

17. Modulation (Power Profile) • This is a transmission of 2 radios in repeater mode. • The guard time specified is for slots power ramping and also Time Advance scenarios. 30ms 2.5ms guard time Slot 1 Slot 2 27.5ms data 1.5ms ramp up /down

18. Voice Call Scenario • Super Frame with Header & Terminator 1 Super Frame … VH A B C D E F VT • Voice calls start with a Voice Header to allow the receiving party to sync and determine if the call is to the intended recipient. • Then the voice data is transmitted in the superframes. • Voice Terminator indicated end of voice call. It must be sent after a voice superframe is complete.

19. Voice Call Scenario • Voice Super Frame (Direct mode) A B C D E F 48 bit sync pattern Emb LC (32 x 4 bit) Null(32 bit) • The first burst of a superframe contain a sync burst. This allows late entry calls. • Embedded LC is sent in the next 4 burst. This LC contains the source ID, destination ID and call type. • The null burst does not contain any embedded signaling data.

20. VF1 VF2 VF3 A B F C D F E F F A Voice Call Scenario • Each Voice Frame (VF) = 20 ms (72 bits) • Each Slot will contain 3 VF AMBE+2 Encode 30 mS 60 mS AMBE+2 Decode

21. Data Call Scenario • Data transmissions do not carry embedded LC information (always sync) • Confirmed and Unconfirmed data send • Header • Data Blocks • Last Data Block • Confirmed Data Response • Header • Data Blocks (Only if destination requests retransmission of blocks that failed block CRC)

22. IP datagram of arbitrary length Break into fragments ….. Fragment 1 Fragment 2 Fragment n Break into blocks Building a data packet, which may have two header blocks Block m is the last data block of a fragment ….. Hdr Block Block 1 Block m Time 2 1 2 1 2 1 2 1 2 Data Call Scenario Data Message Decomposition • Message broken up into fragments • Data Packet composed of • Data Header • Message/Fragment data

23. Repeater TX Alert Req Idle Idle Hdr Hdr Idle Idle Idle Idle Idle Idle Idle Idle ACK ACK Idle Idle Idle Idle Idle Idle Idle Idle Voice Voice Idle Idle 2 1 2 1 2 1 2 1 2 1 2 1 2 1 1 2 1 2 1 2 1 2 1 2 1 2 1 2 MS1 TX Alert Req Hdr Hdr Voice Voice Voice Voice 1 2 1 2 1 2 1 2 1 2 1 2 1 2 MS2 TX ACK ACK Time Time Repeater Voice Call Scenario Individual Call via repeater • This is a case of one subscriber making an individual call to another subscriber. • Request and ACK are Data Bursts (Data Slot Type = Control) • Voice Header is a Data Burst (Data Slot Type = Voice LC Header)

24. Data Sync Voice Sync Voice Sync Voice Voice Voice Voice Voice Voice Voice Burst Burst Burst Burst Burst Burst Burst Voice Term Data Sync Data Sync Voice Sync Voice Sync Data Sync Data Sync Voice Voice LC LC Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Voice Burst Burst Hrd Hrd Burst Burst Burst Burst Burst Burst Burst Burst Burst Burst Burst Burst Term Term A A B B C C E E F D D Superframe = 360 msec Superframe = 360 msec Burst Structure (Generic)

25. TDMA burst center TDMA burst center SYNC or embedded signaling SYNC or embedded signaling Payload Payload Payload Payload Timeslot 1 Timeslot 2 30,0 ms 30,0 ms 2,5 ms TDMA frame Burst Structure (Rptr Inbound) Subscriber #1 Subscriber #2 Subscriber Inbound TX TDMA Frame in Repeater Mode

26. TDMA burst center CACH burst center TDMA burst center SYNC or embedded signaling SYNC or embedded signaling Payload Payload Payload Payload CACH CACH CACH CACH CACH CACH Timeslot 1 Timeslot 2 30,0 ms 30,0 ms 2,5 ms TDMA frame Burst Structure (Rptr Outbound) Repeater Outbound TX TDMA Frame

27. Burst Structure (Generic Sync) Generic Burst With Sync • Inbound Voice Sync Pattern • Outbound Voice Sync Pattern • Inbound Data Sync Pattern • Outbound Data Sync Pattern • Reverse Channel Sync Pattern • Inbound/outbound sync patterns • Voice/data sync patterns • Reverse channel sync pattern • Direct Mode uses only Inbound Sync Patterns • This is one of the essential Patents by Motorola.

28. Vocoder Frame 1 Vocoder Frame 2 Vocoder Frame 3 VC1 VC2 VC3 Frame 1 (72) Frame 3 (72) Frame 2 (36) Frame 2 (36) SYNC (48) 27,5 msec Burst Structure (Voice w/ Sync) Voice Burst with Sync • Vocoder DVSI AMBE+2 (Enhanced Half Rate) • 3600 bps for voice + FEC • 2450 bps voice • 1150 bps FEC • Three 20 msec vocoder frames per Voice Burst • 60 ms audio per burst

29. EMB (8) EMB (8) PI LCSS CC EMB Parity Voice (108) Voice (108) Embedded signaling (32) 27,5 ms Burst Structure (Voice w/ Emb) Voice Burst With Embedded Signaling • EMB (Embedded Framing) • CC (Color Code) – Differentiates signaling that originates at another site • PI (Privacy Indicator) – Status of scrambling/encryption • LCSS (LC Start Stop) – Indicates that this burst contains the beginning, end, or continuation of embedded signaling • Parity – FEC Parity bits for EMB field • Embedded Signaling - Call type, Source and Destination IDs (Link Control information)

30. Data Type CC FEC Parity Slot Type (10) Slot Type (10) FEC Parity SYNC or embedded signaling (48) Info (98) Info (98) 27,5 ms Burst Structure (Data/Control) Voice LC Header Terminator with LC Control Block Data Header Rate ½ Data Rate ¾ Data Idle Data/Control Burst • Info – Data or control payload + FEC • CC (Color Code) – Differentiates signaling that originates at another site • Data Type – Indicates the type of control or data that is being carried • FEC Parity – Golay (20,8) FEC Parity bits for Slot Type field

31. Burst Structure (CSBK) • 96 bit CSBK (80 bits of signaling + 16 bits of CRC) can be carried in a single data/control • Use for radio command such as Radio Check, Radio Uninhibit/Inhibit, Call Alert and Radio Unit Monitor.

32. CACHsignaling AT TC LCSS FEC Outboundburst Outboundburst CACH (24) CACH (24) CACH (24) CACH CACH CACH 30,0 ms 30,0 ms TDMA frame Burst Structure (CACH) • AT (Access Type) – Indicate whether slot is busy or idle • TC (TDMA Channel) – Indicates whether inbound and outbound burst is channel 1 or 2 • LCSS (LC Start Stop)– Indicates that this burst contains the beginning, end, or continuation of CACH signaling • CACH Signaling (4 CACH) – This contains a Short LC burst for scan time improvement. • FEC – FEC Parity bits for CACH Burst

33. Bandwidth: 12.5kHz Modulation Type: 4FSK (4 level Frequency Shift Keying) Channel Type: 2-Slot TDMA. Data rate: 9600 bits/second Single slot protocol data rate outbound: 4800 bits/second Single slot protocol data rate inbound: 4400 bits/second Single slot voice data rate (Voice with FEC data rate): 3600 bits/second Single slot raw data payload rate: 1600 bits/second. Audio Throughput Delay: ~400ms System Access Time: Group Call, Direct Mode, With TPT = ~600ms Group Call, Repeater Mode, With TPT = ~1000ms Individual Call, Direct Mode, With TPT = ~1100ms Individual Call, Direct Mode, With TPT = ~1500ms Protocol Specifications

34. The cause of the delays is purely in the software. It can be due to buffering delays and encoding and decoding delays due to the chosen protocol. The DMR protocol is expected to have a much longer audio throughput delay compared to Analog systems. The Analog System Delays can be in the order to 20 to 40ms. However the Digital System Delays can be in the order of 300ms to 500ms. This large delays is mainly due to the slotting of the voice and also the voice compression adaptation time. Audio Throughput Delay Talk Permit Tone Audio (1kHz Tone) Press PTT Tx Audio Throughput Delay Audio (1kHz Tone) Rx

35. System access time Talk Permit Tone Audio (1kHz Tone) Press PTT Tx System Access Time Audio (1kHz Tone) Rx

36. Possible Future Improvements

37. TX TX Traffic Traffic Reverse Burst Transmission Tx Radio 1 1 1 1 1 1 1 1 TX TX TX TX TX TX TX TX TX TX Traffic Traffic Traffic Traffic Traffic Traffic Traffic Traffic Traffic Traffic Rx Radio Tx Reverse Burst Time Time • Rx radio is able to Tx a short burst of control information to the Tx radio. • This burst can be used for feature like Tx interrupt, Rx Ack, Power control…..

38. Reverse Burst Power • The instantaneous power must be contained within the mask • Since the slot is only 10ms, there will not be any risk of inter-slot interference.

39. Single Frequency Repeater System Only one 12.5kHz B W channel for inbound and outbound traffic Tx on one slot, repeated on other slot

40. Full duplex calls is where it operates like a hand-phone where the Tx and Rx audio is going on simultaneously. This will require Slot 1 to be used as Tx and Slot 2 to b used as RX. However in doing this, the Tx to Rx time is only 2.5ms and thus is too short to allow the HW locking to happen. This is currently not possible with current HW technology. TDMA burst center TDMA burst center SYNC or embedded signaling SYNC or embedded signaling Payload Payload Payload Payload Timeslot 1 Timeslot 2 30,0 ms 30,0 ms 2,5 ms TDMA frame Full Duplex Calls

41. Direct Mode 2-Slot operation 30ms Radio Unit (A) Radio Unit (B) uC RF RF uC Radio C user presses PTT Radio Unit (C) Radio Unit (D) uC RF RF uC • The DMR protocol does support 2 simultaneous calls in direct mode operation. • This new operational feature is an addition to the DMR protocol to overcome this limitation. • Basically, when A is transmitting to B, Radio C will also be able to transmit to D after locking on to radio A’s timing.

42. Pseudo Trunk Operation 30ms 30ms Rptr Busy Idle Busy Busy Idle Radio Unit (B) Radio Unit (A) RF uC uC RF Radio Unit (C) Radio Unit (D) uC RF uC RF • In the defined DMR protocol, the radios will be allocated to a specific repeater slot and only use that slot even-though the other slot is not busy. • This new protocol is to allow radios to utilize any slot number if it is idle (No Activity). • Imagine Radio A is transmitting a private call to radio B. • Radios in the vicinity of the repeater (C and D) will see that there is a Idle slot and can decide to use it.

43. Another feature that is planned to be included in future products is a new calling mode. This new calling mode will allow a use to specifically select a couple of radio users to be re-allocated to a temporary group ID to have a call. This mode of operation is like a Skype conference call when you can select a couple of people to join a voice call. HYT HYT HYT HYT HYT HYT HYT Conference Call (DGNA) Send temporary regrouping to selected target radios.