Contents 1. Introduction
LT codes are the first realization of a class of erasure codes that we call universal erasure codes. The symbol length for the codes can be arbitrary, from one-bit binary symbols to general ℓ-bit symbols. We analyze the run time of the encoder and decoder in terms of symbol operations, where a symbol operation is either an exclusive-or of one symbol into another or a copy of one symbol to another. If the original data consists of input symbols then each encoding symbol can be generated, independently of all other encoding symbols, on average by symbol operations, and the original input symbols can be recovered from any of the encoding symbols with probability by on average symbol operations.
