Research On Turbo Decoding Technology In LTE System

With the higher demand for mobile communication,3rd Generation Partnership Project start the standardization project of Long Term Evolution(LTE).LTE is to increase the rate of data transmission and to increase the utilization rate of spectrum with reducing the transmission delay of system.Because of approaching the theoretical limit of Shannon and excellent performance in bit error rate,the Turbo code draw the attention of people who are in the filed of mobile communication.In the system of 3GPP LTE,the Turbo code is used to the coding scheme of Error correction in physical down-chain.This paper first introduces the theory and the structure of Turbo codes and the coding of Turbo code in LTE system.Then it introduces the theory and the structure of Turbo decoder.And it also introduces the commonly used decoding algorithm of Turbo,such as MAP,Log-MAP,Max-Log-MAP and SOVA.With the analysis and comparison of computational complexity and decoding performance of these algorithms by theory analysis and matlab simulation,the algorithm of Log-MAP is chosen as the Turbo decoding algorithm in hardware circuit.Then In this paper,the Turbo encoder and Turbo decoder is designed and implemented based on FPGA with the algorithm of Log-MAP. In the part of design and implementation of Turbo code in FPGA,the Turbo encoder of convolutional code encoder and the interleaver in recursive system is designed and implemented.The Turbo decoder in data quantification, data calculation, the soft input component decoder and the soft output component decoder is also designed and implemented.Finally,this paper simulate resulting picture of each part based on FPGA.According to the same result of output and input in Turbo decoder and encoder,the result of simulation is correct.And the scheme of design and implementation that the algorithm of Log-MAP used in Turbo encoder and Turbo decoder is feasible.