PTP EX: HIGH-RATE FRONT-END TELEMETRY AND
COMMAND PROCESSING SYSTEM
Item type
text; Proceedings
Authors
Ozkan, Siragan
Publisher
International Foundation for Telemetering
Journal
International Telemetering Conference Proceedings
Rights
Copyright © International Foundation for Telemetering
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30-Dec-2017 16:52:00
Link to item
http://hdl.handle.net/10150/608315
PTP EX:
HIGH-RATE FRONT-END TELEMETRY AND COMMAND
PROCESSING SYSTEM
Siragan Ozkan
Avtec Systems, Inc.
ABSTRACT
This paper describes the PTP EX, a 160 Mbps Telemetry and Command front-end
system, which takes advantage of the state-of-the-art in networking and software
technology, and the rapid development in PC components and FPGA design.
Applications for the PTP EX include High-rate Remote Sensing Ground Stations,
Satellite/Payload Integration and Testing, High-rate Bit Error Rate Test (BERT) System
and High-rate Digital Recorder/Playback System.
The PTP EX Interface Board, the MONARCH-EX PCI High Speed Frame
Synchronizer/Telemetry Simulator with Reed-Solomon Encoder/Decoder, is designed
with the following key capabilities:
• 160 Mbps serial input for CCSDS Frame Processing (Frame Synchronization, Derandomization, CRC, Reed-Solomon decoding, time stamping, quality annotation,
filtering, routing, and stripping);
• 160 Mbps disk logging of Reed-Solomon corrected CCSDS frames with simultaneous
real-time processing of spacecraft engineering data and ancillary payload data;
• Onboard CCSDS Telemetry Simulation with 160 Mbps serial output (Sync Pattern,
background pattern, ID counter, time stamp, CRC, Reed-Solomon encoding,
Randomization, and Convolutional encoding);
• Bit Error Rate Testing up to 160 Mbps (Pseudo-random transmitter and receiver with
bit error counter).
The innovative architecture of the MONARCH-EX allows for simultaneous logging of a
high-rate data stream and real-time telemetry processing. The MONARCH-EX is also
designed with the latest in field-programmable gate array (FPGA) technology. FPGAs
allow the board to be reprogrammed quickly and easily to perform different functions.
Thus, the same hardware can be used for both Telemetry processing and simulation, and
BERT applications.
The PTP EX also takes advantage of the latest advances in off-the-shelf PC computing
and technology, including Windows NT, Pentium II, PCI, Gigabit Ethernet, and RAID
subsystems. Avtec Systems, Inc. is leveraging the PTP EX to take advantage of the
continuous improvement in high-end PC server components.
KEY WORDS
CCSDS, Reed-Solomon Coding, Data Logging, and Level-Zero Processing.
INTRODUCTION
Avtec Systems, Inc. PTP EX is a High-rate CCSDS Front-end Telemetry and Command
Processing System. Applications for the PTP EX include High-rate Remote Sensing
Ground Stations, Satellite/Payload Integration and Testing, High-rate Bit Error Rate Test
(BERT) System and High-rate Digital Recorder/Playback System.
The PTP EX Interface Board, the MONARCH-EX PCI-based High Speed Frame
Synchronizer/Telemetry Simulator with Reed-Solomon Encoder/Decoder, is designed
with the following capabilities:
•
•
•
•
160 Mbps serial input for CCSDS Frame Processing (Frame Synchronization, Derandomization, CRC, Reed-Solomon decoding, time stamping, quality annotation,
filtering, routing, and stripping)
160 Mbps disk logging of Reed-Solomon corrected CCSDS frames with
simultaneous real-time processing of spacecraft engineering data and ancillary
payload data
Onboard CCSDS Telemetry Simulation with 160 Mbps serial output (Sync Pattern,
background pattern, ID counter, time stamp, CRC, Reed-Solomon encoding,
Randomization, and Convolutional encoding)
Bit Error Rate Testing up to 160 Mbps (Pseudo-random transmitter and receiver
with bit error counter)
The PTP EX also supports CCSDS Telecommand (including COP-1), however this paper
focuses on the Telemetry Processing capabilities of the system.
CCSDS PACKET TELEMETRY OVERVIEW
The Consultative Committee for Space Data Systems (CCSDS) has outlined a series of
recommendations designed to promote standardization between missions, spacecraft, and
member organizations. The recommendations on Packet Telemetry promote
standardization in the end-to-end transport of mission data from application processes in
space to distributed user application processes in space or on Earth.
In Packet Telemetry, multiple spacecraft processes generate data packets. The size and
rate at which these packets are generated can vary depending on the requirements of the
on-board process. A packet identifier header is then prepended to the data packets, and
the variable size packets are inserted into fixed length Transfer Frames. Packets may span
multiple Transfer Frames, up to the maximum allowed packet size.
Each Transfer Frame has a header containing a frame identifier field and frame sequence
count information. The frame identifier field is used to define which Virtual Channel
group that a particular Transfer Frame belongs. Virtual Channelization provides a method
for organizing and prioritizing Transfer Frames. A particular Virtual Channel (VC) can
be assigned for a specific type of data. For example, VC 0 is typically used for real-time,
mission-critical and spacecraft housekeeping data. Other VCs can be assigned for
playback telemetry or image data.
Once the Transfer Frame is created, it can optionally be encoded prior to transmission
over a RF link. CCSDS defines a concatenated coding scheme with an inner
Convolutional code and an outer Reed-Solomon code with block interleaving.
Additionally, a CRC checksum can be added, and the data can be Randomized prior to
transmission. Figure 1 is a diagram of an encoded Transfer Frame with Packets.
Encoded CCSDS Transfer Frame
Unencoded CCSDS Transfer Frame
Frame
Transfer Frame
Sync
Primary Header
(1ACFFC1D)
Packet
Header
Var. Size
Data
Packet
………
Packet
Header
Var. Size
16-bit R-S CHECK
Data
CRC SYMBOLS
Packet
CCSDS
Data
Packet
Figure 1: CCSDS Transfer Frame
As shown in Figure 1, the CRC checksum is calculated and appended to the end of the
Transfer Frame. The Reed-Solomon codeblock is then generated and appended after the
CRC. After the Reed-Solomon code is added, the Transfer Frame can be Randomized
and Convolutionally encoded.
PTP EX SYSTEM ARCHITECTURE
The PTP EX System is based on the architecture of a standard PC server. A block
diagram of the PTP EX system is shown in Figure 2. The standard PC architecture,
Windows NT operating system, and the PCI bus allow for upgrade of all peripherals. No
proprietary bus, CPU, or system architecture is used except for the MONARCH-EX PCIbased Frame Synchronizer/Telemetry Simulator with Reed-Solomon Encoder/Decoder.
The PTP EX system contains dual Pentium II 400 MHz processors with 256 MB
SDRAM, built-in 10/100 Base T Ethernet, a 2 GB Ultra/Wide mirrored SCSI system hard
drive, a CD-ROM drive, and a 1.44 MB floppy drive. The system’s dual processors,
mirrored system hard drive, and redundant hot swap power supplies provide high
availability for mission critical applications.
The PTP EX system is configured with the Windows NT operating system and Avtec’s
PTP NT software. The PTP NT software controls all aspects of the PTP EX system.
PTP-9015
UltraSCSI
RAID
CPU 1
Disk
Array
S
C
S
I
CPU Local Bus
CPU 2
Host/PCI
Cache/
Bridge
CPU Local Bus
Ultra SCSI
Adapter
Graphics
Adapter
Memory Bus
AVD 96-058-09
Main Memory
PCI
Bridge
PCI Bus
LAN
Adapter
SCSI
RAID
Adapter
S
C
S
I
LAN
System
Disks
CD
ROM
B
u
s
ISA
Bridge
STD
PC
I/O
I
S
A
E
x
p
a
n
s
i
o
n
B
u
s
PCI Bus
RD
PTPNT-6500
MONARCH-EX
Frame Sync
Simulator
RS Codec
PTP-8020
ISA-STG2
Time Code
Processor
RT
8
RT
ST
8
PTPNT-6500TM0
MONARCH-EX
Transition
Module
HIGH-RATE
TELEMETRY
ST
TT
SD
IRIG or 10 MHz/1 PPS
Figure 2: Block Diagram of PTP EX System
PTP NT SOFTWARE OVERVIEW
The PTP NT software controls all aspects of the system, including data flow and board
configurations, via software modules. Each module represents physical interfaces
including the network, disk, and Frame Synchronizer/Telemetry Simulator, as well as
software processes such as the CCSDS Virtual Channel Processor, Packet Processor, and
the File Recorder. All modules are loaded onto the PTP NT Desktop. Figure 3 is a
sample PTP NT Desktop with modules loaded and configuration windows open. Each
module has its own configuration and status windows, specific to the component it
represents. Once loaded, the modules can be connected in various ways to control data
flow and input/output via the easy-to-use Graphical User Interface (GUI). The PTP NT
can be controlled locally or remotely via a network socket interface.
Figure 3: Sample PTP NT Desktop
MONARCH-EX OVERVIEW
The MONARCH-EX Frame Synchronizer/Telemetry Simulator with Reed-Solomon
Decoder/Encoder is a two PCI board set. The MONARCH-EX baseboard performs all
frame processing including Frame Synchronization, Derandomization, Reed-Solomon
decoding, and Data Sorting based on Spacecraft ID and Virtual Channel ID at rates up to
160 Mbps. The MONARCH-EX baseboard also performs Telemetry Simulation at rates
up to 160 Mbps. The MONARCH-EX is a bi-directional board, and as such, can
simultaneously receive and process a 160 Mbps data stream, while simulating telemetry
using onboard memory.
The MONARCH-EX accepts clock and data inputs via a differential ECL interface. The
input/output interface on the MONARCH-EX is provided through a Transition Module,
which resides in an adjacent PCI slot. The MONARCH-EX Transition Module is
connected to the MONARCH-EX baseboard via two 8-bit parallel mezzanine busses. A
block diagram of the MONARCH-EX is shown in Figure 4. The Transition Module
provides the differential ECL serial interface and a Frequency Synthesizer for generating
an internal transmit clock. The Transition Module converts the serial input stream to a
parallel data stream and passes the parallel data to the MONARCH-EX base board for
frame processing. The Transition Module accepts a parallel data stream from the
MONARCH-EX baseboard and converts the data to a serial stream for output.
Serial Input Channel
Filter Table
256KB
F
I
F
O
32
32
Transition Module
(MONACO)
RT
Receiver
FPGA
16KB
F
I
F
O
Serial Input Logic
Archive Data
32
RT
Serial to
Parallel
Converter
8
RD
Real-Time Data
32
P
C
I
F
I
F
O
ReedSolomon
Decoder
PCI
Interface
B
u
s
Serial Output Logic
ReedSolomon
Encoder
ST
Frequency
Synthesizer
256KB
MUX
2:1
F
I
F
O
32
S
R
A
M
TT
ST
Transmitter
FPGA
128KB
Parallel to
Serial
Converter
8
SD
32
Serial Output Channel
Figure 4: MONARCH-EX Block Diagram
PTP EX TELEMETRY PROCESSING
Figure 5 outlines the PTP EX System’s CCSDS Telemetry Processing capabilities. The
Coding Layer and Transfer Layer (Virtual Channel filtering) functions are all performed
in hardware (MONARCH-EX). Packet Layer processing and data distribution is
accomplished by the PTP NT software. Optionally, Transfer Layer functions can be
performed in software.
CLCWs
Physical
Waveform
TM
symbol
stream
Physical
layer
(Receiver/
Demodulator)
Reed Solomon decoder
Coding
layer
Derandomizer
Frame synchronizer
TM
frames
Transfer
layer
TM
frame
data
field
Packet
layer
TM
packets
Viterbi decoder
Telemetry
TCP/IP
TCP/IP
and Disk
and Disk
Interfaces
Interfaces
TM frames
MONARCH-EX Hardware Layers
PTP NT Software Layers
Figure 5: PTP EX CCSDS Telemetry Processing
HIGH RATE TELEMETRY ACQUISITION
The MONARCH-EX accepts high rate serial data in NRZ-L, S, or M format at rates up to
160 Mbps. It performs frame synchronization with auto-polarity correction, derandomization, and Reed-Solomon error checking and correction (including VCDU
header), and CRC error detection. The MONARCH-EX supports CCSDS Version 1 and
Version 2 frame formats and service grades 2 and 3. All of the Frame Synchronizer, Derandomizer, and Reed-Solomon decoding and error correction parameters are user
programmable and can be bypassed. The MONARCH-EX appends a time tag with 1
microsecond accuracy and quality annotation to each frame that is received. The quality
annotation includes the following fields: Frame Sync State, Autopolarity Flag, Bit Slip
Flag, Loss of Sync Flag, CRC Check Flag, and Reed-Solomon Error
Detection/Correction statistics.
The MONARCH-EX routes frames of data to the Archive path and/or real-time path
based on a user specified field in the frame header. The MONARCH-EX contains a
programmable filter that can be used to route frames of telemetry based on any 32-bit
field within the first 16 bytes of the frame. For CCSDS frames, this allows filtering based
on a combination of Spacecraft ID (SCID) and Virtual Channel ID (VCID). For nonCCSDS frames, this filter can be used to route based on sub-frame ID, or any other 32-bit
field. Frames can be routed to the real-time path or the Archive path, both paths, or
discarded. The data routing is accomplished using a Filter Table located in a Content
Addressable Memory (CAM), which offloads a large portion of work from the CPUs.
The Real-time telemetry is then passed along the real-time data path and taken in by the
PTP NT for software processing. This includes AOS service processing and
encapsulation for network transmission via TCP/IP.
The archive data is transferred directly from the MONARCH-EX to an UltraSCSI
controller in a peer-to-peer fashion without CPU intervention. The Archive telemetry
with quality annotation and time tag is logged to a single file on the UltraSCSI RAID
system at rates up to 160 Mbps. The data file can be processed post pass to sort service
data units into separate files for distribution.
The PTP maintains cumulative data quality statistics, including: count of frames received,
frames archived, frames sent to the real-time path, frames with CRC errors, frames with
RS errors, uncorrectable RS errors, bit slips, and dropouts.
SOFTWARE TELEMETRY PROCESSING (PTP NT)
The PTP NT software performs real-time service processing and network transmission.
The PTP NT software can also be used to perform service processing and network data
transfer on archive data post pass. The PTP EX real-time service processing data rates
vary based on frame length, packet length, and the type of processing required (Virtual
Channel processing and/or Packet processing).
The PTP provides support for both Version 1 (Conventional) and Version 2 (Advanced
Orbiting Systems) of the CCSDS recommendations for packet telemetry. The PTP
supports the following Conventional CCSDS services: Source Packet, Privately Defined
Data, Frame Secondary Header, and the Operational Control Field. The PTP supports the
following CCSDS AOS services: Encapsulation, Multiplexing, Bitstream, Virtual
Channel Access (VCA), Virtual Channel Data Unit (VCDU), and Insert.
The PTP supports service data unit processing using a collection of software modules.
For example, the CCSDS Virtual Channel Processor Module de-multiplexes a data
stream based on Virtual Channel ID. The sorted outputs of the Virtual Channel Processor
module can be routed to File Recorder modules so that each individual virtual channel
can then be logged to independent binary files. Selected service data units can also be
transmitted in real-time over a TCP/IP socket to the local or remote host computers using
the Network Sockets Module. PTP NT also provides a Packet Processor module that
extracts CCSDS packets from selected VCDUs for network transfer or archive. These
packets can then be written to independent, binary files based on APID (Application
Process Identifier). The Bit Stream module extracts bit stream service data units from
selected VCDUs for network transfer or archive. Each service processor module provides
quality annotation based on the operations performed. The PTP service data processing
and routing is completely user definable.
The PTP provides several ways to send data over a TCP/IP network. The PTP will
autonomously send selected real-time telemetry to a TCP/IP (client or server) or UDP/IP
socket port. The PTP also supports IP Multicast so that real-time telemetry data can be
sent to multiple hosts simultaneously. A number of encapsulation modules are available
to format the data prior to network transmission, including NASCOM RTP, IPDU,
SFDU, LEO-T, and EDOS. The PTP’s 100 Mbps Ethernet interface supports network
transfer rates up to 10 Mbytes/sec. The actual network transfer rate depends on the
selected protocol (TCP or UDP), the amount of network congestion, and the distance to
the remote host (TCP acknowledge delay).
SIMULATION AND TESTING
The PTP provides the capability to simulate telemetry data for testing. The PTP can
generate a CCSDS or TDM telemetry streams based on user definable parameters for the
header fields and source data. The PTP can also transmit a stream read from hard disk or
received from the network. The telemetry simulator parameters can be programmed via
the local interface or by the host controller.
The MONARCH-EX generates telemetry frames and outputs serial clock and data at
rates up to 160 Mbps. The MONARCH-EX Telemetry Simulator can read frame data
from the PCI bus, or build frames from host provided data that is stored in onboard
memory (CAM). The MONARCH-EX can overlay a sync pattern, ID counter, and time
stamp before passing the frame to the encoders. The output channel performs CRC
encoding, Reed-Solomon encoding, pseudo-randomization, and convolutional encoding.
The MONARCH-EX can be equipped with an optional Bit Error Rate Tester module.
The Bit Error Rate Tester (BERT) provides the capability to transmit and receive pseudorandom number codes for end-to-end system testing. The BERT supports 160 Mbps full
duplex operation. The BERT module supports the following pseudo-random patterns:
127 bit:
511 bit:
2047 bit (forward):
2047 bit (reverse):
32K bit:
1M bit:
8M bit:
x7 + x6 + 1
x9 + x5 + 1
x11 + x9 + 1
x11 + x2 + 1
x15 + x14 + 1
x20 + x17 + 1
x23 + x18 + 1
The BERT receiver uses a digital correlator to synchronize to the input data stream. This
technique reduces sync loss due to noisy data. The receiver maintains the following
statistics: computed bit error rate, bits received, bits in error, bit slips, and dropouts.
PTP EX CCSDS TELEMETRY PROCESSING PERFORMANCE
The PTP EX system performance varies based on several parameters. The first parameter
being the type of data processing required – archiving only, archiving and real-time
routing, Virtual Channel processing, Packet processing, and/or Network distribution. The
other parameters include transfer frame length (for Virtual Channel processing), and
packet length (for Packet processing).
The direct archiving capability of the PTP EX has been tested at rates up to 200 Mbps.
Since data is passed directly between the MONARCH-EX and the RAID Controller, with
the CPU only responsible for setting up the DMA transfers between the two, CPU
utilization (averaged between two processors) is limited to 10-15% at 200 Mbps.
The PTP EX can perform real-time Virtual Channel processing in hardware or software.
The PTP EX can process frame telemetry (i.e. filter based on VCID) at rates exceeding
9,000 frames per second. The rate varies based on the size of the transfer frame. Figure 6
graphs the performance of the PTP EX versus frame length. The frame lengths used were
derived from varying levels of interleave of the Reed-Solomon codeblock. An interleave
depth of 1 is used for the 259 byte frame, up to an interleave depth of 8 for the 2044 byte
frame.
The PTP EX can also perform real-time Packet processing in software (PTP NT). Packet
processing involves extracting the multiple packets that may be embedded within each
transfer frame. Each packet’s header contains an Application Process Identifier (APID).
The PTP NT filters and sorts packets based on APID. The PTP EX can perform real-time
Packet processing at rates up to 85 Mbps.
2044
Frame Length (Bytes)
1789
1534
1264
1024
769
514
259
0
2000
4000
6000
8000
10000
12000
14000
Frames per Second
Figure 6: PTP EX Frame Processing Performance
Additionally, once the data has been processed at the Virtual Channel or Packet level, the
data can be distributed via a network sockets interface. The PTP NT provides the built-in
capability to transmit and receive data via TCP/IP, UDP/IP or Multicast. Processed
frames and packets can be transmitted real-time via UDP at up to 40 Mbps on a Fast
Ethernet (100 Mbps) network. All network transfer rates are limited by the amount of
available bandwidth on a particular LAN. Table 1 outlines these results.
Table 1: PTP EX Telemetry Processing Performance Specifications
Direct RAID Archiving
Virtual Channel Processing
Packet Processing
Network Transfer
Up to 200 Mbps
>9,000 frames per second
Up to 85 Mbps
Up to 40 Mbps
SUMMARY
The PTP EX High-rate CCSDS Front-end Telemetry and Command Processing System is
based on Avtec’s field-proven PTP NT software and next generation CCSDS board, the
MONARCH-EX. The standard system architecture allows for ease in upgrading and
keeps overall cost down.
The MONARCH-EX board architecture offloads processes from the system CPUs and
uses the PCI bus at maximum efficiency. This is accomplished by sorting the real-time
data and payload data onboard, providing a direct route from the MONARCH-EX to the
Ultra/SCSI RAID subsystem for archiving the payload data via the PCI bus, and passing
only the low-rate real-time data to the system for further processing.
The above features allow the PTP EX to be ideally suited for High-rate Remote Sensing
Ground Stations, Satellite/Payload Integration and Testing, High-rate BERT and Highrate Digital Recorder/Playback System applications.