7,123 research outputs found
Asymptotic Analysis of Plausible Tree Hash Modes for SHA-3
Discussions about the choice of a tree hash mode of operation for a
standardization have recently been undertaken. It appears that a single tree
mode cannot address adequately all possible uses and specifications of a
system. In this paper, we review the tree modes which have been proposed, we
discuss their problems and propose remedies. We make the reasonable assumption
that communicating systems have different specifications and that software
applications are of different types (securing stored content or live-streamed
content). Finally, we propose new modes of operation that address the resource
usage problem for the three most representative categories of devices and we
analyse their asymptotic behavior
Band Codes for Energy-Efficient Network Coding with Application to P2P Mobile Streaming
A key problem in random network coding (NC) lies in the complexity and energy
consumption associated with the packet decoding processes, which hinder its
application in mobile environments. Controlling and hence limiting such factors
has always been an important but elusive research goal, since the packet degree
distribution, which is the main factor driving the complexity, is altered in a
non-deterministic way by the random recombinations at the network nodes. In
this paper we tackle this problem proposing Band Codes (BC), a novel class of
network codes specifically designed to preserve the packet degree distribution
during packet encoding, ecombination and decoding. BC are random codes over
GF(2) that exhibit low decoding complexity, feature limited and controlled
degree distribution by construction, and hence allow to effectively apply NC
even in energy-constrained scenarios. In particular, in this paper we motivate
and describe our new design and provide a thorough analysis of its performance.
We provide numerical simulations of the performance of BC in order to validate
the analysis and assess the overhead of BC with respect to a onventional NC
scheme. Moreover, peer-to-peer media streaming experiments with a random-push
protocol show that BC reduce the decoding complexity by a factor of two, to a
point where NC-based mobile streaming to mobile devices becomes practically
feasible.Comment: To be published in IEEE Transacions on Multimedi
Sparse matrix-vector multiplication on GPGPU clusters: A new storage format and a scalable implementation
Sparse matrix-vector multiplication (spMVM) is the dominant operation in many
sparse solvers. We investigate performance properties of spMVM with matrices of
various sparsity patterns on the nVidia "Fermi" class of GPGPUs. A new "padded
jagged diagonals storage" (pJDS) format is proposed which may substantially
reduce the memory overhead intrinsic to the widespread ELLPACK-R scheme. In our
test scenarios the pJDS format cuts the overall spMVM memory footprint on the
GPGPU by up to 70%, and achieves 95% to 130% of the ELLPACK-R performance.
Using a suitable performance model we identify performance bottlenecks on the
node level that invalidate some types of matrix structures for efficient
multi-GPGPU parallelization. For appropriate sparsity patterns we extend
previous work on distributed-memory parallel spMVM to demonstrate a scalable
hybrid MPI-GPGPU code, achieving efficient overlap of communication and
computation.Comment: 10 pages, 5 figures. Added reference to other recent sparse matrix
format
S-Net for multi-memory multicores
Copyright ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of the 5th ACM SIGPLAN Workshop on Declarative Aspects of Multicore Programming: http://doi.acm.org/10.1145/1708046.1708054S-Net is a declarative coordination language and component technology aimed at modern multi-core/many-core architectures and systems-on-chip. It builds on the concept of stream processing to structure dynamically evolving networks of communicating asynchronous components. Components themselves are implemented using a conventional language suitable for the application domain. This two-level software architecture maintains a familiar sequential development environment for large parts of an application and offers a high-level declarative approach to component coordination. In this paper we present a conservative language extension for the placement of components and component networks in a multi-memory environment, i.e. architectures that associate individual compute cores or groups thereof with private memories. We describe a novel distributed runtime system layer that complements our existing multithreaded runtime system for shared memory multicores. Particular emphasis is put on efficient management of data communication. Last not least, we present preliminary experimental data
Network Slicing in 5G: Admission, Scheduling, and Security
In the past few decades, there was an increase in the number of devices that have wireless capabilities such as phones, televisions, and home appliances. With the high demand for wireless networking, the fifth generation (5G) of mobile networks was designed to support the different services of new applications. In addition, one of the technical issues that 5G would evolve is the increase in traffic and the need to satisfy the userâs experience. With the evolution of wireless networking and 5G, Network Slicing has been introduced to accommodate the diverse requirements of the applications. Thus, network slicing is the concept of partitioning the physical network infrastructure into multiple self-contained logical pieces which can be identified as slices. Each slice can be customized to serve and meet different network requirements and characteristics. In terms of security, network security has allowed for new security vulnerabilities such as Distributed Denial of Service (DDoS) and resource exhaustion. However, slices can be isolated to provide better resource isolation. In addition, each slice is considered an end-to-end virtual network, operators would be able to allocate resources to the tenants which are the service providers. The isolated resources are controlled by the tenants; each tenant has control over how to use them to meet the requirements of the clients. One of the challenges in network slicing is RAN slicing. The target of RAN Slicing is to meet the QoS requirements of different services for each end-user. However, the coexistence of different services is challenging because each service has its requirements. Each slice must estimate its network demands based on the QoS requirements and control the admission to the slice. To solve this issue, we consider the scenario for the enhanced mobile broadband (eMBB) and the ultra-reliable-low-latency communication (URLLC) use casesâ coexistence, and we slice the RAN based on the priority of the user applicatio
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