135 research outputs found
Streaming Codes for Channels with Burst and Isolated Erasures
We study low-delay error correction codes for streaming recovery over a class
of packet-erasure channels that introduce both burst-erasures and isolated
erasures. We propose a simple, yet effective class of codes whose parameters
can be tuned to obtain a tradeoff between the capability to correct burst and
isolated erasures. Our construction generalizes previously proposed low-delay
codes which are effective only against burst erasures. We establish an
information theoretic upper bound on the capability of any code to
simultaneously correct burst and isolated erasures and show that our proposed
constructions meet the upper bound in some special cases. We discuss the
operational significance of column-distance and column-span metrics and
establish that the rate 1/2 codes discovered by Martinian and Sundberg [IT
Trans.\, 2004] through a computer search indeed attain the optimal
column-distance and column-span tradeoff. Numerical simulations over a
Gilbert-Elliott channel model and a Fritchman model show significant
performance gains over previously proposed low-delay codes and random linear
codes for certain range of channel parameters
Rate-Optimal Streaming Codes for Channels with Burst and Isolated Erasures
Recovery of data packets from packet erasures in a timely manner is critical
for many streaming applications. An early paper by Martinian and Sundberg
introduced a framework for streaming codes and designed rate-optimal codes that
permit delay-constrained recovery from an erasure burst of length up to . A
recent work by Badr et al. extended this result and introduced a sliding-window
channel model . Under this model, in a sliding-window of
width , one of the following erasure patterns are possible (i) a burst of
length at most or (ii) at most (possibly non-contiguous) arbitrary
erasures. Badr et al. obtained a rate upper bound for streaming codes that can
recover with a time delay , from any erasure patterns permissible under the
model. However, constructions matching the bound were
absent, except for a few parameter sets. In this paper, we present an explicit
family of codes that achieves the rate upper bound for all feasible parameters
, , and .Comment: shorter version submitted to ISIT 201
Subset Adaptive Relaying for Streaming Erasure Codes
This paper investigates adaptive streaming codes over a three-node relayed
network. In this setting, a source transmits a sequence of message packets
through a relay under a delay constraint of time slots per packet. The
source-to-relay and relay-to-destination links are unreliable and introduce a
maximum of and packet erasures respectively. Recent work has
proposed adaptive (time variant) and nonadaptive (time invariant) code
constructions for this setting and has shown that adaptive codes can achieve
higher rates. However, the adaptive construction deals with many possibilities,
leading to an impractical code with very large block lengths. In this work, we
propose a simplified adaptive code construction which greatly improves the
practicality of the code, with only a small cost to the achievable rates. We
analyze the construction in terms of the achievable rates and field size
requirements, and perform numerical simulations over statistical channels to
estimate packet loss probabilities
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