-
Inserts the EMWIN service into LRIT with minimal service latency
and minimal bandwidth overhead
-
Complies with CGMS & CCSDS and supports NOAA LRIT VC priority
scheme
-
Allows re-use of existing EMWIN S/W or new TCP/IP based EMWIN S/W
-
D6 S/W supports simultaneous RS-232 & TCP/IP interfaces
-
TCP/IP Socket (internal & external) output for newer S/W
-
RS232 to support legacy EMWIN user S/W
NOAA LRIT System Architecture
![graphic depiction of the LRIT Architecture](images/ppt_presentation/slide2.gif)
CGMS Communication Model
![CGMS Communication Model](images/ppt_presentation/slide3.png)
LRIT Domain 4 Existing Design
Domain 4 Context
![Domain 4 Context for the existing design](images/ppt_presentation/slide5.png)
Communication Processor
-
Monitors arrival of LRIT files received from Preprocessor via FTP.
-
Implements Session, Transport, Network, and partial Datalink CGMS
layers.
-
Sends CADUs to Uplink Processor via IPDU interface.
-
Uplink Processor implements remainder of Datalink layer as well as
physical layer
Domain 4 Architecture
![Graphic of the Domain 4 Architecture](images/ppt_presentation/slide7.png)
Domain 5 Uplink Processor (No Changes)
LRIT Domain 5
Domain 5 Context
![Domain 5 Context](images/ppt_presentation/slide5.png)
Domain 5 Specification
Processing Detail |
LRIT Specification |
Domain 4 VCDU |
7136 bits, CCSDS, MSB first |
Out-of-Band VCDU |
7136 bits, CCSDS, MSB first |
ASM |
Hexadecimal '1ACFFC1D' |
Reed-Solomon |
(255,223, I=4) not including ASM |
CADU |
8192 bits (including ASM & Reed-Solomon) |
Randomization |
h(x)=x8+x7+x5+x3+1;
initialized to all 1s |
Differential Encoding |
Default is NONE; NRZ-M Optional |
Convolution |
(R= 0.5, K=7, NO G2 symbol inversion) |
Constant Clock |
Internal Frequency Synthesizer, or External Clock |
Domain 5 Architecture
![Domain 5 Architecture graphic representation](images/ppt_presentation/slide12.gif)
LRIT Domain 6 Existing Design
LRIT Domain 6 Context
![LRIT Domain 6 hardware context](images/ppt_presentation/slide14.png)
Domain 6 Software Context
![Domain 6 software context](images/ppt_presentation/slide15.png)
Domain 6 Transfer Application
![Domain 6 transfer application graphic](images/ppt_presentation/slide16.png)
-
DLLs implemented as in-process COM Servers
-
Data flow roughly follows layer model
-
Log / Error logging object
EMWIN - LRIT Insertion
-
Carry EMWIN as a bit-stream, but inside a simple file encapsulation
-
Use MPDU + Application Packet (AP)+ LRIT File Headers
-
Use CGMS File Type for mission specific use (128…255). Assign
EMWIN: LRIT file type 214 (0xD6).
-
Group EMWIN RS-232 bits into fixed length bit-stream segments
-
Insert each EMWIN bit-stream segment after the LRIT File Header
-
1 VCDU per EMWIN bit-stream file
-
D6 groups file segments, extracts & concatenates, then outputs
serially
-
Preserves minimum latency & low overhead bandwidth feature of
bit-stream
-
LRIT rate = 17.9 frames / sec ; EMWIN rate @ 9.6 = 1.14 frames/sec
-
D6 Output compatible with RS-232 COTS EMWIN S/W (i.e. RealEmwin)
EMWIN Bit-Stream VCDU Format
![EMWIN Bit-Stream VCDU Format](images/ppt_presentation/slide18.gif)
-
For preservation of bandwidth and minimal latency, received EMWIN
Bitstream is segmented into fixed length segments (836 bytes)
-
File creation latency = 836 bytes * input baud rate; file complete
prior to queueing
-
Fixed length segments are encapsulated per CGMS MPDU/AP/LRIT-File
Headers, and sequentially output
-
LRIT File Types 128…255 available for mission specific use
CGMS CCSDS VCDU Header
version number |
set to 1 specifying version-2 CCSDS |
VCDU-ID |
virtual channel data unit identifier as specified by higher layers,
consisting of spacecraft identifier and virtual channel identifier,
set to 63 for fill VCDUs |
VCDU counter |
sequential count (modulo 16777216) of VCDUs on each virtual channel |
signaling field/replay flag
|
set to 0 specifying real-time VCDUs |
D4 Communication Processor Upgrades for New Design
H/W
S/W
-
New Config file S/W monitors config file and implements VC(Priority),
COM port settings (speed, parity, stop/start)
-
Create S/W for receiving bit-stream data (strip start/stop bits)
over RS-232
-
Create S/W for encapsulating bitstream in sequential fixed length
files
-
S/W uses configuration file to select valid data source port
LRIT D4 EMWIN Upgrade
![LRIT Domain 4 EMWIN Upgrade](images/ppt_presentation/slide21.png)
D6 User Terminal Upgrades
H/W
S/W
-
Create S/W for concatenating EMWIN File Type data
-
Output concatenated data as serial stream to sockets
-
Allow routing of received bit-stream data to RS-232 port(s)
-
Allow routing of received bit-stream data to TCP/IP port(s)
Domain 6 Transfer Application
![Domain 6 Transfer Application](images/ppt_presentation/slide23.gif)
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