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. Introduction Why DMR was pursued?
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 And all Public safety equipment has to be migrated by 2013.

4. Introduction Protocol Development History
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

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. Spectrum Efficiency via TDMA
Slot 1
Slot 2
Slot 1
Regulatory emissions mask
Slot 2
Slot 1
time
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. Enhanced Features – Digital Calling and Signaling
One-to-Many
Enables communication with
specific sets of group members
One-to-One
Call and talk privately with a
specific user’s radio
One-to-All
Allows all on the same channel to
hear communications
NOTE: This also applies to Text Messaging where a user can type a message and send to the intended recipients.

11. System Configurations
Direct Mode Configuration
Up-link
Down-link
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. 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)
Repeater
Slot 1 Freq. 1
Slot 2 Freq. 2
Slot 2 Freq. 1
Slot 1 Freq. 2

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

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 = kHz
Symbol 00 = kHz
Symbol 10 = kHz
Symbol 11 = kHz
TX Splatter filter is square root raised cosine (sqrc) with rolloff = 0.2
RX post-discriminator filter is sqrc with rolloff = 0.2

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

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. Voice Call Scenario VF1 VF2 VF3D B E
VF1 VF2 VF3
AMBE+2 Encode
30 mS
60 mS
AMBE+2
Decode
Each Voice Frame (VF) = 20 ms (72 bits)
Each Slot will contain 3 VF

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
Data Blocks (Only if destination requests retransmission of blocks that failed block CRC)

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

23. Repeater Voice Call Scenario
Hdr 1 2
MS1 TX
Repeater TX
MS2 TX
Time
ACK
Voice
Alert
Req
Idle
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. Burst Structure (Generic)D
Voice
Burst LC
Hrd
Data Sync
Superframe = 360 msec
Voice Sync A C E B F
Term
72-bits Voice Frame (20 ms)
48-bits Sync
264 bits = 3 VF + 1 sync/EMB = 72*3 + 48

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

26. Burst Structure (Rptr Outbound)
SYNC or
embedded
signaling
Payload
TDMA
burst
center
CACH
30,0 ms
TDMA frame
Timeslot 1
Timeslot 2
2,5 ms
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. Burst Structure (Voice w/ Sync)
Frame 1 (72)
Frame 2 (36)
Frame 3 (72)
VC1
VC2
VC3
Vocoder Frame 1
Vocoder Frame 2
Vocoder Frame 3
27,5 msec
SYNC (48)
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. Burst Structure (Voice w/ Emb)
27,5 ms CC PI
LCSS
EMB Parity
Voice (108)
Embedded
signaling (32)
EMB (8)
Voice Burst With Embedded Signaling
FEC – Forward Error Correct.
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. Burst Structure (Data/Control)
Voice LC Header
Slot Type (10)
Info (98)
SYNC or
embedded
signaling (48)
27,5 ms
Data Type CC
FEC Parity
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)
CSBK – Control Signaling Block
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. Burst Structure (CACH)AT TC
LCSS
FEC
CACH signaling
CACH
CACH (24)
Outbound burst
CACH
CACH (24)
Outbound burst
CACH
CACH (24)
30,0 ms
30,0 ms
TDMA frame
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. Protocol Specifications
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
TPT – Talk Permit Tone

34. Audio Throughput Delay
Talk Permit Tone
Audio (1kHz Tone)
Press PTT Tx
Audio Throughput Delay
Audio (1kHz Tone) Rx
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.

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

36. Possible Future Improvements
TPT – Talk Permit Tone

37. Reverse Burst Transmission
Tx Radio 1 1 1 1 1 1 1 1 TX
Traffic 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
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
SYNC or
embedded
signaling
Payload
30,0 ms
TDMA frame
Timeslot 1
Timeslot 2
2,5 ms

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
Idle
Busy
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. Conference Call (DGNA)
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
DGNA – Dynamic Group Numbering Assignment
HYT
Send temporary regrouping to selected target radios.
HYT