9,908 research outputs found
Node Repair for Distributed Storage Systems over Fading Channels
Distributed storage systems and associated storage codes can efficiently
store a large amount of data while ensuring that data is retrievable in case of
node failure. The study of such systems, particularly the design of storage
codes over finite fields, assumes that the physical channel through which the
nodes communicate is error-free. This is not always the case, for example, in a
wireless storage system.
We study the probability that a subpacket is repaired incorrectly during node
repair in a distributed storage system, in which the nodes communicate over an
AWGN or Rayleigh fading channels. The asymptotic probability (as SNR increases)
that a node is repaired incorrectly is shown to be completely determined by the
repair locality of the DSS and the symbol error rate of the wireless channel.
Lastly, we propose some design criteria for physical layer coding in this
scenario, and use it to compute optimally rotated QAM constellations for use in
wireless distributed storage systems.Comment: To appear in ISITA 201
HFR Code: A Flexible Replication Scheme for Cloud Storage Systems
Fractional repetition (FR) codes are a family of repair-efficient storage
codes that provide exact and uncoded node repair at the minimum bandwidth
regenerating point. The advantageous repair properties are achieved by a
tailor-made two-layer encoding scheme which concatenates an outer
maximum-distance-separable (MDS) code and an inner repetition code. In this
paper, we generalize the application of FR codes and propose heterogeneous
fractional repetition (HFR) code, which is adaptable to the scenario where the
repetition degrees of coded packets are different. We provide explicit code
constructions by utilizing group divisible designs, which allow the design of
HFR codes over a large range of parameters. The constructed codes achieve the
system storage capacity under random access repair and have multiple repair
alternatives for node failures. Further, we take advantage of the systematic
feature of MDS codes and present a novel design framework of HFR codes, in
which storage nodes can be wisely partitioned into clusters such that data
reconstruction time can be reduced when contacting nodes in the same cluster.Comment: Accepted for publication in IET Communications, Jul. 201
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