22 Janvier – Thesis defense - Vincent Pignoly

14 h Amphi Jean-Paul Dom / Laboratory IMS - Building A31 (Talence campus)

Study of LDPC codes for optical space applications and design of the associated decoders.

Digital communication systems are everywhere in our daily life. The evolution of needs implies the research and development of innovative solutions for future communication systems. Considering space digital communications, most satellites use radiofrequency links to communicate with the Earth. To minimize bandwith usage and increase throughputs, digital communication technologies based on optical links represent an interesting alternative. However, luminous energy is absorbed by particules that are present in the Earth's atmosphere. These perturbations implies new  issues and new coding schemes must be developed to cope with them.
LDPC codes are an error correction code family. Their performance near Shannon's limit makes them an attractive solution for digital communication systems. They have been selected in Wifi and 5G standards to achieve very high throughputs (several Gbps). They were also adopted in CSSDS and DVB-S2 standards for space applications.
This thesis is about the study and the hardware implementation of coding schemes applied on optical links for space digital communication systems. The first contribution is the study of a coding scheme for an optical downlink with a soft input decoder on Earth. In this study, we developed  a hardware architecture capable of implementing the decoding process on FPGA. The designed decoder reaches the expected throughput of 10 Gbps. A second contribution is about the optical uplink that implies hard input decoding in a satellite. Resulting constraints led us to rethink extended Gallager B algorithm. It made possible the develoment of a new architecture that manages the hard input decoding process efficiently while being compliant with space constraints, such as hardware complexity, heat dissipation and throughput (10 Gbps).

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