CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthi Proposal to P1A & P1B Increasing allowed frame lengths and interleaving depths for AOS TM
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 1
Proposal to P1A & P1B
Increasing allowed frame lengthsand
interleaving depths for AOS TM
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 2
Summary
Background
Targeted applications : e.g. Pleiades-HR
Rationale for changes
Impacts w.r.t. blue books
Conclusion
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 3
Background
Present limitations w.r.t. frame length & interleaving :
AOS blue book limits VCDU length to 5 x 223 = 1115 octets when RS is used not consistent with new RS option (239, 255, E=8) introduced in TM
channel coding blue book frame length limitations should be removed from AOS in the
« Yamada » restructured edition
TM channel coding blue book (June 2001) limits transfert frame (VCDU) length to :
1115 octets (RS(223,255)), 1195 octets (RS(239,255)) when RS is used interleaving depths for RS , I = 1, … , 5
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 4
Background (cnt ’d)
Packet TM blue book max frame length of 2048 octets (max capability of 11-bit FHP)
ESA TM channel coding & Packet TM standards allows interleaving depths for RS , I = 1, 2, 3, 4, 5 & 8 max frame length : 2040 octets (both for coded & uncoded cases)
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 5
Background (cnt ’d)
Rationale for theses limitations loss of power efficiency was considered small (for low rate
systems) between I = 5 and [I=8 or 16] for « Conv(7,1/2)+RS(223,255) » over BPSK
approx. 0,4 dB loss (Eb/N0) @ FER = 10-8 (between I=5 and I=8)
provide acceptable frame sync rate for low to medium data rate mission : few kbps to few Mbps
limit the number of packets being lost whenever a frame is lost : optimization in terms of FER ?
limit the complexity of the RS encoder ?
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 6
Background (cnt ’d)
New channel coding options and modulation schemes are being introduced in CCSDS blue books to cover the needs of « bandwidth limited & high rate » earth orbiting missions
RS (239, 255, E=8) code punctured convolutional code (7,1/2) with punctured rates : 2/3, 3/4, 5/6,
7/8 (as per DVB-S standard) Multidimentional Treillis Coded Modulation (MTCM) 8-PSK
modulation scheme
Example of such « bandwidth limited & high rate » missions PLEIADES-HR
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 7
Targeted applications : e.g. PLEIADES-HR
High resolution earth observation satellites :
Mission parameters : sun synchronous orbit : 500 - 800 km resolution (optical) : 0.6 to 2.5 m radiometric precision : 8 to 12 bits/pixel swath : 15 to 60 km instrument data rates : 128 Mbits/s to 2 Gbits/s image compression - Compression Ratio : 3 to 6 :
compressed rate per instrument : 50 Mbits/s to 500 Mbits/s BER requirement : BER < 10-10 to 10-12 due to compression
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 8
Targeted applications : e.g. PLEIADES-HR
Constraints : minisats or small sats :
severely mass & power limited
Payload TM at X-band : 375 MHz in total band limited
Transmission data rates needed : 128 Mbits/s to 600 Mb/s depending on : nb of ground stations, on-board mass memory capacity
Rate can be splitted into up to 4 channels : 150 Mb/s max per channel
standard P/L TM I/F would be a plus for interoperability and standardisation of equipment in multimission X-band recieving stations
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 9
Targeted applications : e.g. PLEIADES-HR
PLEIADES-HR payload TM characteristics 0.65 m resolution, 20 km swath
620 Mb/s of user data rate to ground at X-band 4 carriers : 155 Mb/s user data rate each MTCM 8-PSK modulation @ 2.5 bits/symbol (compliant with future
CCSDS recommendation) RS (238,254) used as outer code, interleave depth : 5, 8 or 16 ?
required BER of 10-12
due to image compression
compressed image data formated as CCSDS source packets each packet contains 8 compressed lines (for a portion of swath)
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 10
Targeted applications : e.g. PLEIADES-HR
packets inserted in AOS frames AOS selected because of high rates (24-bit frame counter) Insert zone of transfer frame used to carry 12 bytes of ancillary data
interest on this project to develop generic equipment with interfaces based on non-proprietary standards
equipments : image compression unit, mass memory, modulator standard I/F :
CCSDS image lossy compression (algorithm & source format) ? CCSDS source packet AOS VCDU, AOS CVCDU and CADU CCSDS 8-PSK RF interface.
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 11
Rationale for changes
2 penalties identified for PLEIADES-HR w.r.t. CCSDS compatibility
transfer frame format overhead due to limited allowed frame length
loss of power efficiency on the link due to limited allowed interleaving depth for RS outer code
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 12
Rationale for changes (ctn ’d)
Frame format overhead overhead
VCDU frame header : 6 octets M-PDU header : 2 octets Insert : 12 octets
ancillary data sampled @ 8 Hz max Frame rate : 5 kHz @ I=16, 16 kHz @ I=5
Interleavingdepth I
VCDU data fieldlength (octets)
Frame formatoverhead
5 1170 1.71 %
8 1884 1.06 %
16 3788 0.53 %
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 13
Rationale for changes (ctn ’d)
Vast oversampling of ancillary data
frame sync rate much higher than needed
between I=5 and I=16 represents a net capacity loss of 7.5 Mbps
as a reference SPOT5 TM proprietary format has an overhead of : 0.52%
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 14
Rationale for changes (ctn ’d) Loss of power efficiency
comparison of BER (and FER) performance for various interleave depth of the RS(238, 254) outer code
I = 5, I = 8, I = 16 and infinite interleave
2 modulation schemes taken as reference MTCM 8-PSK @ 2 bits/symbol MTCM 8-PSK @ 2.5 bits/symbol (PLEIADES-HR)
2 performance levels in terms of BER : 10-10
10-12
simulations were feasible down to BER=10-9 (typ.) extrapolations were done for lower BER
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 15
Rationale for changes (ctn ’d)
Simulations were cross-verified by experiment on modulator breadboard : for I = 16 only implementation losses (FI 720 MHz w.r.t. simus) were
substracted 0.2 dB @ 2b/symbol 0.32 dB @ 2.5 b/symbol
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 16
BER of MTCM 2b/symbol concatenated with RS(254,238) = f(Eb/No in dB) with interlace size as parameter
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
4,3 4,5 4,7 4,9 5,1 5,3 5,5 5,7 5,9 6,1 6,3
I = 1
I = 2
I = 5
I = 7
I = 8
I = 16
I = 16 (mes)
I = infini
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 17
BER of MTCM 2.5b/sym concatenated with RS(254,238) = f(Eb/No in dB) with interlace size as parameter
1,0E-10
1,0E-9
1,0E-8
1,0E-7
1,0E-6
1,0E-5
1,0E-4
1,0E-3
1,0E-2
1,0E-1
5,80 6,00 6,20 6,40 6,60 6,80 7,00 7,20 7,40
I = 1
I = 5
I = 7
I = 8
I = 16
I = 16 (mes)
I = infini
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 18
Rationale for changes (ctn ’d)
1st case : MTCM 8-PSK @ 2 bits/symbol
Eb/N0 (dB)Interleavedepth I
BER = 10-10 BER = 10-12
5 + 0.55 + 0.70
8 + 0.28 + 0.36
16 + 0.06 + 0.10
Infinite ref ref
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 19
Rationale for changes (ctn ’d)
2nd case : MTCM 8-PSK @ 2.5 bits/symbol
Eb/N0 (dB)Interleavedepth I
BER = 10-10 BER = 10-12
5 + 1.10 + 1.51
8 + 0.37 + 0.54
16 + 0.11 + 0.12
Infinite ref ref
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 20
Rationale for changes (ctn ’d)
I = 8 gives a 1 dB gain @ 10-12 over I = 5 for 8-PSK 2.5 b/s/Hz
I= 16 gives a 0.4 dB gain @ 10-12 over I = 8 for 8-PSK 2.5 b/s/Hz
very significant gain for power constrained spacecraft transmiting at 600 Mbps
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 21
Proposed changes to existing Blue Books
1st solution : add I = 8 as a valid interleaving depth for RS impacts TM channel coding blue book impacts AOS blue book if frame length constraints left in that
book frame length constraints will be removed anyway from that book in
the restructured version
2nd solution : add I = 8 and I = 16 as valid interleaving depths for RS impacts TM channel coding blue book impacts AOS blue book
need to use one of the 5 spare bits of the M-PDU header to have a 12-bit First Header Pointer (minor change).
CCSDS P1A/B Meeting - Frascati - Nov 8, 2001 - Gilles Moury, Guy Lesthievent - 22
Conclusion
2nd solution (add I=8 & 16) is our preferred solution
I=16 provides near optimal performance in terms of power
improves significantly the suitability of CCSDS AOS and TM channel coding to high rate / power&bandwidth constrained systems
changes to existing books are minor but impact on existing AOS infrastructure is to be assessed