ARQ with Doped Fountain Decoding

Abstract

Abstract-We analyze the benefits of an automatic repeatrequest (ARQ) scheme employed in doped belief-propagation decoding for increasing the throughput of fountain encoded data transmissions. The proposed doping mechanism selects doping symbols randomly from the set of input symbols contributing to degree-two output symbols. Here an output symbol is the encoded symbol whose code-graph links to input symbols decoded thus far have been severed. This doping approach always ensures releasing of at least one output symbol, thus increasing the number of degree-one output symbols (the ripple). Using a random walk analysis, we study the belief propagation decoding with degree-two random doping for a fountain code with symbols drawn from an Ideal Soliton distribution. We show that the decoding process is a renewal process whereas the process starts all over afresh after each doping. The approximate interdoping process analysis revolves around a random walk model for the ripple size. We model the sequence of the ripple size increments (due to doping and/or decoding) as an iid sequence of shifted and truncated Poisson random variables. This model furnishes a prediction on the number of required doping symbols and, furthermore, the ARQ throughput cost analysis. We also find that the Ideal Soliton significantly outperforms the Robust Soliton distribution in our ARQ-doping scheme.

Rateless Coding with Feedback

“…The authors thank Philip J. Schroeder for simulating some experiments presented in this paper, Moshe Laifenfeld for useful discussions, and the anonymous referees for drawing our attention to the work in [13]. This work was completed while Andrew Hagedorn was an intern at Deutsche Telekom Laboratories.…”

“…Though there has been work on coding with feedback as a form of hybrid ARQ, for example doped fountain code [13] where feedback is used to restart LT decoding when a ripple has stopped, our work focuses on situations where sender and receiver share some (undetermined) common data. We compare our approach to LT codes and RT codes through extensive experimental data on a simulator and on sensor motes.…”

Rateless feedback codes

“…While the existing schemes are designed for the extreme cases, m = k and m = 0, the more practical assumptions pose an interesting problem. An approach called doped fountain coding is proposed in [3], where the receiver feeds back information on undecoded symbols. This makes the transmitter able to transmit input symbols, which accelerate the decoding process.…”

Low Complexity Doped Wireless Broadcast for Multimedia Applications

“…The doped broadcast streamlines several related feedbackassisted decoding mechanisms, including inactivation [7] and doping [8], [9]. Doping guarantees small overhead and closeto-linear decoding but requires feedback.…”

“…Doping guarantees small overhead and closeto-linear decoding but requires feedback. It refers to fetching a required coded symbol directly from the source, whenever needed to ensure that the peeling decoder continues with its linear decoding process without stalling [8], [9]. Inactivation delays the fetching, via free intermediate decoding variables, until the end of the first decoding stage.…”