Fountain code and its application over Y-network

In channel coding, traditional codes are rate-fixed.  These channel codes usually cannot achieve high throughput and reliability at the same time. What’s more, these fixed-rate codes are not suitable for multicast and broadcast transmission.  To solve these problems, fountain codes are born. Fountain codes can provide limitless encoded bits just like a fountain provide endless supply of water drops. That means fountain codes are rateless. In this thesis report, LT code which is the first practical realization of fountain codes is discussed.  The encoding and decoding details and the degree distributions used are studied. Fountain codes are firstly designed for internet applications where the channels transmitted through are modeled as erasure channels. In this thesis, performances of LT codes are investigated over both binary erasure channel and additive white Gaussian channel. What’s more, the application of fountain codes over Y-network is studied.  In the thesis, the relay node in the Y-network will perform simple coding to enable the receiver to receive encoded bits and at the same time using the advantage of fountain codes. The performance is compared with two other schemes. And it can be seen from our simulations that the application over Y-network can achieve rather good results. These results can be used for future research.