Design of Degree Distributions for Finite Length LT Codes

Abstract

In this paper we investigate the design of degree distributions for finite length LT codes over the binary erasure channel. A decreasing ripple size in literature provides the state of the art degree distributions for finite length LT codes. However, study on releasing multiple encoding symbols in each decoding step shows that the ripple size increases first and then decreases during the decoding process. Therefore, we propose the corresponding ripple size evolution model considering multiple releases. In the design procedure with any ripple size evolution models, the computational cost increases greatly as the length of source symbols increases. Thus, we design a suboptimal degree distribution of low computational complexity. The proposed degree distributions are compared to others through simulations and a increase in performance with respect to block error rate is provided.