Binary Erasure Channels (BEC) can be used to model transmission erasures, for example, symbol erasures in TCP’s link layer and network layer. In order to tackle the erasures incurred, the transceiver system relies on retransmission of the lost packets using acknowledgment and repeat request based schemes. This missing packet information or acknowledgments can be conveyed by the receiver to the ...

This work investigates reliable wireless broadcast with asynchronous data access. A wireless broadcast system based on LT-codes, a realization of the recently introduced Fountain codes, is introduced. We review the traditional problem formalization for Fountain codes operating on erasure channels and generalize the framework to arbitrary types of channels coining the terminology and the concept...

The Luby Transform (LT) codes are the first practical realization of fountain codes. LT codes were designed for efficient use over erasure channels. However, the degree distributions designed for the Binary Erasure Channel (BEC), such as the Robust Soliton Distribution (RSD) which are asymptotically and universally optimal over the BEC, are not optimal over noisy channels. Research has been don...

We study improved degree distribution for Luby Transform (LT) codes which exhibits improved bit error rate performance particularly in low overhead regions. We construct the degree distribution by modifying Robust Soliton distribution. The performance of our proposed LT codes is evaluated and compared to the conventional LT codes via And-Or tree analysis. Then we propose a transmission scheme b...

This dissertation focuses on fountain codes under maximum likelihood (ML) decoding. Fountain codes are a class of erasure correcting codes that can generate an endless amount of coded symbols and were conceived to deliver data files over data networks to a potentially large population of users. First Luby transform (LT) codes are considered, which represent the first class of practical fountain...

Fountain codes are a class of rateless codes well-suited for communication over erasure channels with unknown erasure parameter. We analyze the decoding of LT codes, the first instance of practical, universal Fountain codes. A set of interest during LT decoding is the set of output symbols of reduced degree one (the “ripple”). The evolution of the ripple size throughout the decoding process is ...

We study and compare three coded schemes for single-server wireless broadcast of multiple description coded content to heterogeneous users. The users (sink nodes) demand different number of descriptions over links with different packet loss rates. The three coded schemes are based on the LT codes, growth codes, and randomized chunked codes. The schemes are compared on the basis of the total num...

We study the multicast authentication problem when an opponent can drop, reorder and introduce data packets into the communication channel. We first study the packet authentication probability of a scheme proposed by Lysyanskaya, Tamassia and Triandopoulos in 2003 since our opponent model is based on theirs. Using a family of rateless codes called Luby Transform codes (LT codes) we design a pro...

The automatic coding of clinical documents is an important task for today’s healthcare providers. Though it can be viewed as multi-label document classification, the coding problem has the interesting property that most code assignments can be supported by a single phrase found in the input document. We propose a Lexically-Triggered Hidden Markov Model (LT-HMM) that leverages these phrases to i...