IRIG-106 CHAPTER 7
TELEMETRY DOWNLINK
ETTC JUNE 2015
Balázs Bagó
Zodiac Data Systems
IRIG106 CHAPTER 7
PRESENTATION OVERVIEW
Topics:
•
•
•
•
Idea behind it
Key elements
Some examples
Benefits
Presentation length: 15 Minutes
CURRENT AIRBORNE SYSTEM
ARCHITECTURES
Recorders (Total Data Capture)
• Capturing high rate raw data of all on-board
communications, video (HD/SD), high rate analog and
output from FTI Encoders
• Recorded data is in IRIG106 Chapter 10 Format
Encoders
•Capturing selected transducers and data from busses for
insertion into Time Division Multiplexed PCM Data
Streams
•Trend: Network output from Telemetry Encoders
TELEMETRY DOWNLINK
METHODS TODAY
• Most Telemetry today utilizes IRIG 106, Class I or II,
Chapter 4 PCM stream formats
• Tedious job to match periodically sampled data and
asynchronous data placing into the PCM Stream
• It can be challenging and requires extensive testing
• Often requires excess bandwidth to insure data is
not missed
• Ground decommutation requires extensive
testing for proper measurement placement and
sampling into the PCM stream
• Dynamic reconfiguration is difficult
TECHNOLOGY EVOLUTION
OBSERVATIONS
• Extensive build up around IRIG 106 Ch10 file and Chapter
10 UDP live data streaming
• Moving toward Network Telemetry
• Quick look only requires PC with network connection to
verify all data types
• Many COTS Software Applications are enabled to handle
Ch10 File and UDP live streaming
• Post Mission Processing centered around Ch10 files
IRIG106-15 CHAPTER 7
TELEMETRY DOWNLINK
• Will be released as part of IRIG106-15
• Based on PCM technology as carrier
• Using Time Division Multiplexed Packet Telemetry
methods based on CCSDS
• Allowing transmission of various packetized data:
Chapter 10, Ethernet data, TmNS (iNET) packets, …
• Chapter 7 does not require any programming assignment
of data in the Ch4 PCM stream which is typically required
for traditional PCM Encoders
CHAPTER 7: MULTIPLEXING DATA
INTO ASYNCHRON PACKETS
Chapter 10
Video
Packets
Streaming
Ethernet Data
(e.g. TmNS)
Fill Packet,
Status
Information
TM DOWNLINK FORMAT
• First Header Pointer method used from CCSDS Packet
Telemetry concept (both Frame Synch and Header are 32 bits)
• First Header Pointers help synchronization or
resynchronization in case of transmission errors
First Header Pointer
Frame Sync
Header
Fill
Ch10 Packet
Ethernet Packet Frame Sync
Minor Frame
(IRIG106 Chapter 4 PCM Standard)
LOW LATENCY DATA HANDLING
• Low Latency Packet mechanism helps keeping
packetization overhead low and inserting time critical data
anywhere into the stream
• Flag in the frame header allows, that the low latency data
can overtake standard packets
• Latency can be kept below 20ms for critical data
Low Latency Data
F
S
Pck #N
F
S
Pck #N
F L
S L
Pck #N
F
S
Pck #N
Transfer packets may overlap transfer frames
PROTECTING STRUCTURE
CRITICAL ELEMENTS
• Transmission errors can lead to multiplied error rate, if
they are modifying the data interpretations (e.g. altering
structure length or data type information).
• Extended Golay coding is used to protect structure critical
information, as:
• Frame Headers, Packet Header data type and packet length
information, Length and Data Type information in Chapter
10 and TmNS headers
• Extended Golay (24,12,8) code corrects 3 of 24 transmitted
bits with 100 % overhead on structure critical elements
• Simple realization possible with small look-up tables
ADDITIONAL ERROR CORRECTION
AND RANDOMIZATION
• Additional error correction or data randomization
methods are NOT part of Chapter 7
• Reed-Solomon, LDPC or other error correction
methods shall be included in telemetry
transmitters and receivers
• Randomized PCM code: IRIG106 Chapter 4 is
increasing the error rate by factor 3, so CCSDS
additive randomization is to be considered.
PACKET HEADER CODING
23
22
21
Reserved
11
10
20
19
18
Content
9
8
17
16
15
Fragment
7
6
5
4
14
13
12
Length (15..12)
3
2
1
0
Length (11..0)
Content: Packet Content (bits 21..18)
Fragment: Packet Fragmentation.
0000: Fill Packet
(bits 17..16).
0001: Application Specific Packet
0010: Test Counter Packet
00: Complete Packet
0011: Chapter 10 Packet
01: First Fragment of a Packet
0100: Raw Ethernet MAC Frame Packet 10: Middle Fragment of a Packet
0101: Ethernet IP Packet
11: Last Fragment of a Packet
0110: iNET TmNS Packet
0111 – 1111: reserved
Length. (bits 15..0)
Splitted to 2x12 bits, transmitted as 2 x 24 bits Golay(24,12,8)
VIDEO APPLICATION EXAMPLE
HD High Bit Rate H.264
Video Ch10 Encoding
On-Board
Video Camera
On Board High Rate Recording
HD Video
Interface
On Board Chapter 10 Streaming
Frame Rate Decimation
and/or HD to SD conversion
IRIG106
Chapter 7
Interface
Low Rate PCM Downlink
SIMULTANEOUS LIVE AND RECORDED
DATA TRANSMISSION
All Bus Capture
On Board High Rate Recording
MIL-1553
Interface
On Board Chapter 10 Streaming
BC
RT
Live data, Filtered MIL 1553 Messages
IRIG106
Chapter 7
Interface
Recorded data from the recording media
Low Rate PCM Downlink
GROUND REPRODUCTION SIDE
Quick-look and real-time monitoring
Receiver and bit synchronizer
Selected
Sources
Ethernet gateway
TmNS
Chapter 10 UDP
Ground Recorder
Chapter 7 Native Signal
Reconstruction
PCM
Data+ Clock
Reproduction
of Native Data
Types
Selected
Sources
Traditional
PCM decom
systems
Video, Voice
1553, Analog
Ethernet
IRIG106 CHAPTER 7 TELEMETRY
DOWNLINK SUMMARY
• Totally compatible with TM encryptors, decryptors,
transmitters, receivers, bit syncs
• IRIG106 Chapter 7 Telemetry Downlink can greatly simplify
TM downlink process
• Switching cost is low
• Minimal testing required to setup mission
• Ideal for HD recording and SD Video downlink
• Ethernet gateway applications with priority handling
• Low latency is achievable
• Ideal for missions with quick reaction dynamic data
requirements
THANK YOU !