Simulation Research On The Performance Of Bicm-ID And Implementation Of Its Fixed-Point Number Decoding

Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is first proposed by Xiao dong Li and others and introduced it to the soft feedback BICM system. BICM-ID system combines coding and modulation technology, and reduces the error rate through repeatedly transmission information between the demodulator and decoder. BICM-ID system could not only achieve excellent performance under Rayleigh channel, but also improve the BICM system performance under AWGN channel. So, as it was presented, many academics started to research it.This paper first briefly describes the basic components of BICM-ID system, including encoding/decoding, interleaving/solution and modulation/demodulation. The paper mainly introduces the principle of convolution encoding and decoding and demapping algorithm. Encoding aspects we introduce the polynomial method, the state diagram method, tree graph method and the grid method. There are two major decoding algorithms, the probability decoding domain MAP decoding algorithm and logarithmic domain MAP decoding algorithm. Demapping section formula is deduced in detail, and laid the groundwork for a later chapter of simulation.This paper first briefly describes the basic components of BICM-ID system, which mainly including encoding/decoding, interleaving/solution, modulation/demodulation. The principles of convolution encoding, decoding and demapping algorithm are described. In the encoding aspect, the polynomial method, diagram method, tree and graph method and grid method are introduced. In the decoding aspect, the probability domain MAP decoding algorithm and log domain decoding algorithm for MAP are introduced. At the same time, demapping part gives detailed formulas.There are many factors that can affect system performance of BICM-ID, this paper mainly studies the code length, the influence of the number of iterations and the way of mapping. Three kinds of influence factors simulation curve are given respectively under AWGN channel and Rayleigh channel. This article adopts 8PSK and 16 QAM modulation modes. Each modulation mode has 6 different mapping ways and gets the BER curve which is in accordance with the Harmonic Mean of the Minimum Squared Euclidean Distance criterion. Finally this paper gives EXIT simulation curve of the performance of specific mapping method under different SNR and different ways of mapping under a certain SNR.Finally, in order to make the BICM-ID system be further promoted and more extensive application, the paper studies the fixed-point decoding. We make the detailed introduction and simulation for the factors of clipping level and fixed-point.