The Research Of Bit-Interleaved Coded Modulation

With the rapid development of modern digital communication technology, coded modulation technique caused extensive concern of the academia and the tech world for its high spectrum efficiency and high transmission reliability. Traditional coded modulation scheme can achieve the effective encoding in additive white Gaussian noise (AWGN) channel, but if used to study the fading channel, the performance will get a rapid deterioration, so the coded modulation scheme with joint optimization of coded modulation technology and interleaved technology--bit-interleaved coded modulation (BICM) arises at the historic moment. The design principle of BICM is to place a bit interleaver between the encoder and the modulator, in the case of ideal interleaving, encoder and modulator can be designed independently, in order to improve the BICM system performance in fading channel. BICM has been widely used in various commercial wireless communication systems, in the next field of optical communication may also achieve large-scale application, its research has important theoretical and practical significance.This paper mainly introduces the principle of BICM and the key theory that can be used in error probability analysis process. The paper mainly studies the error probability performance of BICM system in AWGN channel and nonlinear optical fiber transmission channel. In AWGN channel, because its channel transfer function is known, according to the current research on saddle point approximation method, simulate and verify its key variables, such as log-likelihood ratio, cumulant generating function. For optical fiber channel, due to the influence of the loss, dispersion and nonlinear in the fiber, the noise cannot be directly regarded as a uniform white noise, and its channel transfer function is also unknown. So in this paper we choose Monte Carlo method together with related optical simulation software, compare and analysis the error probability of BICM system in the nonlinear optical fiber channel and AWGN channel, and present the scope when AWGN channel model is used in nonlinear fiber channel.