14,987 research outputs found
Weakly Secure MDS Codes for Simple Multiple Access Networks
We consider a simple multiple access network (SMAN), where sources of
unit rates transmit their data to a common sink via relays. Each relay is
connected to the sink and to certain sources. A coding scheme (for the relays)
is weakly secure if a passive adversary who eavesdrops on less than
relay-sink links cannot reconstruct the data from each source. We show that
there exists a weakly secure maximum distance separable (MDS) coding scheme for
the relays if and only if every subset of relays must be collectively
connected to at least sources, for all . Moreover, we
prove that this condition can be verified in polynomial time in and .
Finally, given a SMAN satisfying the aforementioned condition, we provide
another polynomial time algorithm to trim the network until it has a sparsest
set of source-relay links that still supports a weakly secure MDS coding
scheme.Comment: Accepted at ISIT'1
Decentralized Erasure Codes for Distributed Networked Storage
We consider the problem of constructing an erasure code for storage over a
network when the data sources are distributed. Specifically, we assume that
there are n storage nodes with limited memory and k<n sources generating the
data. We want a data collector, who can appear anywhere in the network, to
query any k storage nodes and be able to retrieve the data. We introduce
Decentralized Erasure Codes, which are linear codes with a specific randomized
structure inspired by network coding on random bipartite graphs. We show that
decentralized erasure codes are optimally sparse, and lead to reduced
communication, storage and computation cost over random linear coding.Comment: to appear in IEEE Transactions on Information Theory, Special Issue:
Networking and Information Theor
Effective Scheduling for Coded Distributed Storage in Wireless Sensor Networks
A distributed storage approach is proposed to access data reliably and to cope with node failures in wireless sensor networks. This approach is based on random linear network coding in combination with a scheduling algorithm based on backpressure. Upper bounds are provided on the maximum rate at which data can be reliably stored. Moreover, it is shown that the backpressure algorithm allows to operate the network in a decentralized fashion for any rate below this maximum
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