Raptor Codes with LT-LDPC Precoding Performance Analysis and FPGA Optimization

Abstract

Raptor codes are designed to effectively handle packet loss and erasures as a type of fountain code, capable of generating an unlimited number of encoded symbols from source informations, which is particularly useful in scenarios where the number of transmissions is unknown or variable. Luby Transform (LT) codes, a kind of fountain code encoding method, exhibit linear complexity, and Low-Density Parity-Check (LDPC) codes can be constructed by the generator matrix and the parity-check matrix. The LT-LDPC pre-coding method combines the advantages of both, enhancing encoding and decoding efficiency. Deploying code on Field-Programmable Gate Arrays (FPGAs) involves several steps: synthesis, place and route, and bitstream generation, followed by loading the bitstream onto the FPGA to configure its internal logic according to the coding methods. This paper introduces a method of encoding and decoding Raptor codes, utilizing the intimal LT codes and the peripheral LDPC codes constructed by PEG. It employs a lop-BP decoding method over noise channels based on the Tanner graph for decoding and deploys the optimized algorithm on FPGA to enhance performance.