Unfolding Graphs for Constructing of Short and Moderate-Length LT Codes
中短长度LT码的展开图构造方法

This paper proposes one construction method for short and moderate-length Luby Transform (LT) codes by unfolding Tanner graphs from every output node as root. For each output node, when the stopping criterion is satisfied, one uncovered input node or one input node on the deepest layer is randomly selected and connected to the root. Two parameters, the unfolding depth threshold and the maximal unfolding depth, are adjusted to control the girth of short cycles and make the range of random selection as large as possible. Simulation shows the performance improvements of the proposed algorithms are obvious compared with the random graph method for short and moderate length LT code.