SLS-CS_12-05Some results on NGU

coding schemesMarco Baldi1, Marco Chiani2, Franco Chiaraluce1, Enrico Paolini2

1 Università Politecnica delle Marche, Ancona, Italy{m.baldi, f.chiaraluce}@univpm.it

2 Università di Bologna, Bologna, Italy{marco.chiani, e.paolini}@unibo.it

SLS-CS_12-05 UnivPM-UniBO_NGU_Input.v2

(128, 64) NASA binary LDPC code

Max Iterations vs Performance

Comparison with non-binary codes

(256, 128) NASA binary LDPC code

Max Iterations vs Performance

Comparison with non-binary codes

(512, 256) NASA binary LDPC code

Max Iterations vs Performance

Binary VS non-binary codes• Short non-binary LDPC codes outperform their binary

counterparts by 1 dB or more

• This appears to be independent of the maximum number of iterations allowed for decoding a received frame

• The convergence speed (in terms of used iterations) of binary and non-binary codes is comparable

• The parity-check matrices of the non-binary codes which have been used as a reference are the same used in:

L. Costantini, B. Matuz, G. Liva, E. Paolini, M. Chiani,«Non-binary protograph low-density parity-check codes for space communications,»Int. J. of Satellite Communications and Networking, Vol. 30, No. 2, pp. 43–51, 2012

Comments on TC Randomization• It has already been observed [Alvarez2006] that, when

used at high data-rates, the CCSDS standard TM randomizer incurs spurious problems

• The problem is mainly due to Only Idle Data (OID) Frames, which are typically filled by zero bits before randomization

• Depending on the mission requirements, some solutions have been studied to ensure suitable randomization of high rate data [Garello2009]

[Alvarez2006] O. Alvarez and G. Lesthievent, “Pseudo-Random Codes for High Data Rate Telemetry: Analysis and New Proposal”, presented at CCSDS RF & Modulation & Channel Coding Working Groups, Rome, Italy, 12 June 2006.

[Garello2009] R. Garello, M. Baldi, F. Chiaraluce, “Randomizer for High Data Rates”, European Space Agency Contract Report, March 2009, ESOC Contract No. 20959/07/D/MRP.

Comments on TC Randomization (2)

• At the Earth's surface, the power flux density (PFD) produced by spacecraft emissions must not exceed prefixed values, fixed by ITU and ECSS

• These limits are those of interest for high data rate TM links

• Concerning NGU links, transmission occurs from Earth to a spacecraft, or between two spacecrafts

• What are the requirements to be considered for spurious frequencies (PFD masks, synchronization issues…)?

• Idle frames in asynchronous uplink services?