Scalable Data Multicast Using Expanding Window Fountain Codes

Digital Fountain (DF) codes were introduced as an efficient and universal Forward Error Correction (FEC) solution for data multicast over lossy packet networks. However, in real-time applications, the DF encoder cannot make use of the “rateless” property as it was proposed in the DF framework, due to its delay constraints. In this scenario, many receivers might not be able to collect enough encoded symbols (packets) to perform succesful decoding of the source data block (e.g., they are connected as a low bit-rate receivers to a high bit-rate source stream, or they are affected by severe channel conditions). This paper proposes an application of recently introduced Expanding Window Fountain (EWF) codes as a scalable and efficient solution for real-time multicast data transmission. We show that, by carefully optimizing EWF code design parameters, it is possible to design a flexible DF solution that is capable of satisfying multicast data receivers over a wide range of data rates and/or erasure channel conditions.