Abstract
Fountain (or rateless) codes are a family of erasure codes where the rate can be adjusted on the fly. LT codes are the first realization of fountain codes, having this beneficial property and low computational complexity in both encoding/decoding as well. However, some disadvantages of LT codes have been perceived, such as the redundancy is optimal only if the amount of source symbols, K, is approaching to infinity. Consequently in decoding, the source decoded rate, R, stays lower than 10% for a very long period, and increases drastically till receiving a certain amount of encoded packets. Currently, there are many strategies to improve the performance of LT codes in the early and/or intermediate stages for the unicasting transmission services. In this thesis, a transmission control strategy of LT codes for the error-prone broadcasting environment is proposed. Our method is simulated-based, which means the sender simulates the decoding status of a large amount of receivers to predicate the distribution of all decoded rates. To enhance the transmission efficiency in broadcasting, according to this estimated decoding status, the sender thus encodes the most beneficial packets and transmits to the receivers. In addition, some other tools to further improve the performance of decoding are given and discussed. The simulation results demonstrate that the proposed strategy promotes the decoded performance in both early and intermediate stages with less redundancy practically. Key words: fountain codes, rateless codes, LT codes, broadcasting environment, simulated-based.