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Performances des codes correcteurs d’erreur LDPC appliqués au lien Fronthaul optique haut-débit pour l’architecture C-RAN du réseau 5G : conception et implantation sur FPGA

Abstract : Nowadays, the architecture of the mobile network is in full evolution to ensure the increase in terms of bit rate between the Central (CO) (core networks) and various terminals such as mobiles, computers, tablets in order to satisfy the users. To address these challenges of the future, the C-RAN (Cloud or Centralized-RAN) network is known as a 5G solution. In the C-RAN context, all BBUs (Base Band Units) are centralized in the CO, only the RRH (Remote Radio Head) remain at the head of the base station (BS). A new segment between BBUs and RRHs appears called "fronthaul". It is based on D-ROF (digital radio-overfiber) transmissions and carries the digital radio signal at a high bit rate using the Common Public Radio Interface (CPRI) protocol. Taking into account CAPEX and OPEX, the ANR LAMPION project has proposed the Self-seeded Reflective Semiconductor Optical Amplifier (RSOA) technology in order to make the solution more flexible and overcome the need for colored transmitters / receivers in the context of PON-WDM (Wavelength Division Multiplexing Passive Optical Network). Nevertheless, it is necessary to add a FEC (forward error corrector) in the transmission to ensure the quality of service. So the objective of this thesis is to find the most suitable FEC to apply in the C-RAN context. Our work has focused on the use of LDPC codes, chosen after performance comparisons with other types of codes. We have specified the parameters (code performance, matrix size, cycle, etc.) required for LDPC codes to obtain the best performance. Hard-decision LDPC algorithms were chosen after considering the tradeoff between circuit complexities and performance. Among these hard-decision algorithms, the GDBF (gradient descent bit-flipping) was the best solution. Taking into account a CAN 2-Bit in the channel led us to propose a variant: the BWGDBF (Balanced weighted GDBF). Optimizations have also been made with respect to the convergence of the algorithm and latency. Finally, we managed to implement our own algorithm on the Spartan FPGA 6 xc6slx16. Several methods have been proposed to achieve a latency of 5 μs desired in the C-RAN context. This thesis was supported by the project ANR LAMPION (Lambada-based Access and Metropolitan Passive Optical Networks).
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Submitted on : Tuesday, March 27, 2018 - 5:02:12 PM
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Ao Li. Performances des codes correcteurs d’erreur LDPC appliqués au lien Fronthaul optique haut-débit pour l’architecture C-RAN du réseau 5G : conception et implantation sur FPGA. Traitement du signal et de l'image [eess.SP]. Université de Limoges, 2017. Français. ⟨NNT : 2017LIMO0110⟩. ⟨tel-01744890⟩

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