一种基于LT码的不等错误保护方法

A Novel Unequal Error Protection Scheme Based on LT Codes

针对在各种恶劣的信道环境中优先保证码流中相对重要数据的正确传输问题,提出了一种改进的基于LT码的不等错误保护(UEP)方案。首先在分析了目前基于LT码的UEP方案中因数据简单舍入操作可能带来性能恶化问题的基础上,提出了将度分布修正系数修改为优先级和输出节点度数的函数并且在计算重要数据节点的度数时采用按概率上下取整操作的改进方案,克服了目前方案中存在的性能恶化问题;然后推导了其在BEC信道中采用最大似然概率(ML)译码时UEP性能的理论上下界;最后对其在多进制删除信道中采用置信传播(BP)算法译码时的UEP性能进行了仿真实验。理论分析和仿真实验的结果都显示,与目前方案相比,该改进方案具有较好的UEP性能,同时增强了设计的灵活性。

Aimed to ensure the correct transmission of most important data in case of the channel＇s performance deterioration,this paper presents a novel unequal error protection scheme based on LT codes.Firstly,the UEP performance deterioration of the alternative UEP scheme,which is caused by the simple rounding operation,is analyzed,and an improved scheme that can avoid the UEP performance deterioration is proposed.In this scheme the bidirectional rounding operations according to different probabilities in degree computations of most important bits are introduced,and the fixed degree skew coefficient is revised to a function of priority and degree of output nodes.Then the upper and lower bounds on the ML decoding error probabilities of MIB and LIB over the BEC are deduced.Finally the UEP performance on the BP decoding over erasure channel is simulated.The theoretical deduction and simulation results show that the proposed UEP scheme has better UEP performance and more flexibility in code design than the alternative UEP schemes.