# Presentation: 388520

##  Proposal to P1A & P1B

** ****Proposal to P1A & P1B**
**Increasing allowed frame lengths**
**and**
**interleaving depths for AOS TM**

## Summary

**Background**** **
**Targeted applications : e.g. Pleiades-HR**** **
**Rationale for changes**** **
**Impacts w.r.t. blue books**** **
**Conclusion **

## 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**

## 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)**** **

## 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 ?**

## 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**

## 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 **

## 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**

## 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)**

## 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.**

## 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**

## 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**

## 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%**

## 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**

## 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**

## Slide 16

## Slide 17

## Rationale for changes (ctn ’d)

**1st case : MTCM 8-PSK @ 2 bits/symbol**

## Rationale for changes (ctn ’d)

**2nd case : MTCM 8-PSK @ 2.5 bits/symbol**

## 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**** **

## 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).**

## 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**