204 research outputs found
Dynamic control of Coding in Delay Tolerant Networks
Delay tolerant Networks (DTNs) leverage the mobility of relay nodes to
compensate for lack of permanent connectivity and thus enable communication
between nodes that are out of range of each other. To decrease message delivery
delay, the information to be transmitted is replicated in the network. We study
replication mechanisms that include Reed-Solomon type codes as well as network
coding in order to improve the probability of successful delivery within a
given time limit. We propose an analytical approach that allows us to compute
the probability of successful delivery. We study the effect of coding on the
performance of the network while optimizing parameters that govern routing
Dynamic Allocation for Resource Protection in Decentralized Cloud Storage
Decentralized Cloud Storage (DCS) networks represent an interesting solution for data storage and management. DCS networks rely on the voluntary effort of a considerable number of (possibly untrusted) nodes, which may dynamically join and leave the network at any time. To profitably rely on DCS for data storage, data owners therefore need solutions that guarantee confidentiality and availability of their data. In this paper, we present an approach enabling data owners to keep data confidentiality and availability under control, limiting the owners intervention with corrective actions when availability or confidentiality is at risk. Our approach is based on the combined adoption of AONT (All-Or-Nothing-Transform) and fountain codes. It provides confidentiality of outsourced data also against malicious coalitions of nodes, and guarantees data availability even in case of node failures. Our experimental evaluation clearly shows the benefits of using fountain codes with respect to other approaches adopted by current DCS networks
Robust live unicast video streaming with rateless codes
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.""©2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."We consider live unicast video streaming over
a packet erasure channel. To protect the transmitted data,
previous solutions use forward error correction (FEC),
where the channel code rate is fixed in advance according
to an estimation of the packet loss rate. However, these
solutions are inefficient under dynamic and unpredictable
channel conditions because of the mismatch between the
estimated packet loss rate and the actual one.We introduce a
new approach based on rateless codes and receiver feedback.
For every source block, the sender keeps on transmitting
the encoded symbols until it receives an acknowledgment
from the receiver indicating that the block was decoded
successfully. Within this framework, we provide an efficient
algorithm to minimize bandwidth usage while ensuring
successful decoding subject to an upper bound on the packet
loss rate. Experimental results showed that compared to
traditional fixed-rate FEC, our scheme provides significant
bandwidth savings for the same playback qualityThis work was supported by the DFG Research Training Group GK-1042
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