QPSK TLM Modes

1
QPSK TLM Modes CCSDS 401 2.4.11 DRAFT 10/15/04
RFM_05-06
Single Data Source Aligned bits Staggered
(offset) bits Coded Dual encoders Single
encoder Uncoded Not covered by 2.4.11 Dual
Data Source (Note 1 says single, serial data
stream ) with Same data rate on each
channel with Different data rate on each channel
(2.4.11 a) says coherent)
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2.4.11 PHASE-AMBIGUITY
RESOLUTION FOR QPSK MODULATION SYSTEMS 1  The
CCSDS,  considering  (a) that resolution of phase
ambiguities in the earth station's receiver is an
inherent problem with systems using coherent
Quaternary Phase-Shift-Keying (QPSK)
modulation  (b) that coding (Constellation
convention, but not decoding) conventions for
QPSK systems are unambiguously defined in CCSDS
Recommendation 401 (2.4.10)  (c) that the
phase ambiguity results from the lack of
transmission of reference phase information, thus
making it impossible for the receiver's carrier
recovery circuitry to select the correct
reference phase from the four possible stable
lock points (Table 2.4.11-1)  (d) that the
phase-ambiguity can be resolved by using the
techniques listed in Figure 2.4.11-1  (e) that
the several methods for resolving the phase
ambiguity depicted in Figure 2.4.11-1 are
evaluated in Table 2.4.11-2  (f) that most
space agencies currently employ differential
encoding and synchronization (sync) markers for
framed data transmission  (g) that any of the
four possible phase states result in an
unambiguously identifiable unique word pattern
according to Table 2.4.11-1 which can be used to
resolve the phase ambiguity  (h) that the sync
markers already existing in the framed data
transmission can be used as the unique words for
resolving the phase ambiguity Note 1
single, serial data stream
V. Sank 9/12/04
3
Can be supported by equipment commonly available
for GN
High Rate Telemetry Single Data Source, Coded
Space Segment
I/Q switch gives ½ bit delay. Actual circuit
may use parallel load
Convolutional Encode
Single Data Source
RS Code Interleave
Transition Generator, Randomizer
High Rate QPSK
Data
Put differential format before convolutional
encode
Convolutional Encode
Frame Synch not randomized
Q channel delay implied by commutator at left
Ground Segment
Convolutional (Viterbi) Decode
Bit/Symbol Synchronizer
Mission Operation Center (MOC)
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Ground Station
Convolutional (Viterbi) Decode
Bit/Symbol Synchronizer
Frame Synch not randomized
Staggered bits and Differential Format Resolves
ambiguity
V. Sank 9/12/04
4
Can be supported by equipment commonly available
for GN
High Rate Telemetry Single Data Source, Coded
Space Segment
I/Q switch gives ½ bit delay. Actual circuit
may use parallel load
Convolutional or LDPC Encode
Single Data Source
RS Code Not requred
Transition Generator, Randomizer
High Rate QPSK
Data
Put differential format before convolutional
encode
Convolutional or LDPC Encode
Frame Synch not randomized
Q channel delay implied by commutator at left
Ground Segment
Frame Synch (soft bits)
Bit/Symbol Synchronizer
Mission Operation Center (MOC)
RS Decode Not required
Frame Synch and Data de- randomizer
Data
Analog bits
Ground Station
Frame Synch (soft bits)
Bit/Symbol Synchronizer
Frame Synch not randomized
Staggered bits and Frame Synch Resolves ambiguity
V. Sank 10/15/04
5
Can be supported by equipment commonly available
for GN
High Rate Telemetry Single Data Source, No inner
code
Space Segment
I/Q switch gives ½ bit delay. Actual circuit
may use parallel load
Single Data Source
RS Code Interleave
Transition Generator, Randomizer
High Rate QPSK
Data
Put differential format before convolutional
encode
Frame Synch not randomized
Q channel delay implied by commutator at left
Ground Segment
Bit/Symbol Synchronizer
Mission Operation Center (MOC)
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Ground Station
Bit/Symbol Synchronizer
Frame Synch not randomized
Staggered bits and Differential Format Resolves
ambiguity
V. Sank 10/15/04
6
Not currently supported by GN but can also be
supported by equipment available for GN.
Supported by USN for Jason
Low Rate Telemetry with Single Encoder
Space Segment
Single Data Source
Convolutional Encode
RS Code Interleave
Transition Generator, Randomizer
g1
Low Rate QPSK
Data
g2
Frame Synch not randomized
Q channel delay ½ symbol SQPSK
Ground Segment
Bit/Symbol Synchronizer
Mission Operation Center (MOC)
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Ground Station
Bit/Symbol Synchronizer
Frame Synch not randomized
If no convolutional coding, Frame Marker can be
used to resolve alternate bit inversion. This
will increase acquisition time and have a SNR
performance impact.
V. Sank 9/12/04
7
Not currently supported by GN but can also be
supported by equipment available for GN.
Supported by USN for Jason
Low Rate Telemetry, Uncoded
Space Segment
Single Data Source
RS Code Interleave
Transition Generator, Randomizer
Low Rate QPSK
No Convolutional Code
Data
Bit n
Bit n1
Frame Synch not randomized
Q channel delay ½ symbol SQPSK
Ground Segment
Data is all true or all inverted, use Frame
Synch to resolve.
Bit/Symbol Synchronizer
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Bit/Symbol Synchronizer
Frame Synch not randomized
I/Q swap is not an issue because stagger insures
correct time ordering of the bits. If no
convolutional coding, Frame Marker can be used to
resolve alternate bit inversion. This will
increase acquisition time and have a SNR
performance impact.
V. Sank 9/12/04
8
Not currently supported by GN but can also be
supported by equipment available for GN.
Supported by USN for Jason
Low Rate Telemetry, Uncoded
Space Segment
DRAFT
Single Data Source
RS Code Interleave
Transition Generator, Randomizer
Low Rate QPSK
No Convolutional Code
Data
Bit n
Bit n1
Frame Synch not randomized
Q channel delay ½ symbol SQPSK
Ground Segment
Data is all true or all inverted
Convolutional (Viterbi) Decode Bypass I or Q
(exclusive) inversion (polarity) must be
resolved. SNR impact
Bit/Symbol Synchronizer
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Bit/Symbol Synchronizer
Frame Synch not randomized
If no convolutional coding, Frame Marker can be
used to resolve alternate bit inversion. OR a
double L to M and M to L format conversion will
resolve the ambiguity. This has an additional .3
dB SNR performance impact.
V. Sank 9/12/04
9
Back Up Slides
V. Sank 9/12/04
10
High Rate Telemetry Dual Data Source
Space Segment
Convolutional Encode
High Rate QPSK
Dual Data Source
Put differential format before convolutional
encode
Frame Synch not randomized
Convolutional Encode
Q channel delay arbitrary due to data rate
difference
Ground Segment
Convolutional (Viterbi) Decode
Bit/Symbol Synchronizer
Analog bits
Convolutional (Viterbi) Decode
Bit/Symbol Synchronizer
If Data 1 and Data 2 have different data rate,
Sort by data rate at bit synchronizer. If data
rates are the same and Frame marker is the same
sort by VCID.
V. Sank 9/12/04
11
C/NOFS, Swift, GLAST Low Rate Telemetry with
Single Encoder
Space Segment
PN Transmitter Often purchased as component.
Single Data Channel
20 Kbps
40 Ksps
40 Ksps
RS Code Interleave
Transition Generator, Randomizer
Low Rate QPSK
Data
40 Ksps
Frame Synch not randomized
I and Q PN codes out of phase.
300 Ksps max
Ground Segment
Inversion must be resolved
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Frame Synch not randomized
V. Sank 11/19/03
12
TDRSS High Rate Telemetry Signal Flow Block
Diagram
Section B.3.3.1 a)
Fig B-6 Data Conditioner
Space Segment
I/Q switch gives ½ bit delay. Actual circuit
may use parallel load
g1g1g1g1g2g2g2g2
Convolutional Encode (up to 8 encoders, Fig B-10
lower left)
Transmitter Often purchased as component.
Fig B-6 DG2
Single Data Channel
Fig B-6 Data Source
Fig B-8
RS Code Interleave
Transition Generator, Randomizer
High Rate QPSK
Data
Put differential format before convolutional
encode
Convolutional Encode (up to 8 encoders, Fig B-10
lower left)
Fig B-6 DG2
Fig B-8
Frame Synch not randomized
Fig B-6 Data Source
Q channel delay implied by Commutator at left,
SQPSK
Fig B-6 Data Conditioner
300 Msps max
Ground Segment
Convolutional (Viterbi) Decode (Up
to 8)
Bit/Symbol Synchronizer
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Data
Analog bits
Convolutional (Viterbi) Decode (Up
to 8)
Bit/Symbol Synchronizer
Frame Synch not randomized
Figure references are to the SNUG Rev 8
V. Sank 11/9/03
13
Can NOT be supported by equipment commonly
available for GN due to DG1, spread spectrum
TDRSS Low Rate Telemetry Signal Flow Block Diagram
Section B.3.2.1 a)
Space Segment
Identical data on I and Q but not BPSK due to
spreading. Convo symbols serial, not staggered
Transmitter Often purchased as component.
Fig B-6 DG1
Single Data Channel
RS Code Interleave
Transition Generator, Randomizer
Low Rate QPSK
Data
Fig B-6 DG1
Frame Synch not randomized
Data Conditioner Fig B-7
Q channel delay ½ chip for spectral reasons
KSA, SSA, MA, SMA and DAS
300 Ksps max
Ground Segment
Analog bits
RS Decode Deinterleave
Frame Synch and Data de- randomizer
Inversion resolved at PN level
Data
Frame Synch not randomized
Balanced Power Single Data Source Identical Data
on I/Q Channels (KSA, SSAR, MA, SMA, DAS)
Figure references are to the SNUG Rev 8
V. Sank 2/18/04
14
Section B.3.2.1 b)
Balanced Power Single Data Source Alternate I/Q
Bits (SMAR, SSAR, DG1 Mode 1 or 2, Nor
available on MA or DAS)
V. Sank 11/18/04