627 research outputs found
Will SDN be part of 5G?
For many, this is no longer a valid question and the case is considered
settled with SDN/NFV (Software Defined Networking/Network Function
Virtualization) providing the inevitable innovation enablers solving many
outstanding management issues regarding 5G. However, given the monumental task
of softwarization of radio access network (RAN) while 5G is just around the
corner and some companies have started unveiling their 5G equipment already,
the concern is very realistic that we may only see some point solutions
involving SDN technology instead of a fully SDN-enabled RAN. This survey paper
identifies all important obstacles in the way and looks at the state of the art
of the relevant solutions. This survey is different from the previous surveys
on SDN-based RAN as it focuses on the salient problems and discusses solutions
proposed within and outside SDN literature. Our main focus is on fronthaul,
backward compatibility, supposedly disruptive nature of SDN deployment,
business cases and monetization of SDN related upgrades, latency of general
purpose processors (GPP), and additional security vulnerabilities,
softwarization brings along to the RAN. We have also provided a summary of the
architectural developments in SDN-based RAN landscape as not all work can be
covered under the focused issues. This paper provides a comprehensive survey on
the state of the art of SDN-based RAN and clearly points out the gaps in the
technology.Comment: 33 pages, 10 figure
Partial-indistinguishability obfuscation using braids
An obfuscator is an algorithm that translates circuits into
functionally-equivalent similarly-sized circuits that are hard to understand.
Efficient obfuscators would have many applications in cryptography. Until
recently, theoretical progress has mainly been limited to no-go results. Recent
works have proposed the first efficient obfuscation algorithms for classical
logic circuits, based on a notion of indistinguishability against
polynomial-time adversaries. In this work, we propose a new notion of
obfuscation, which we call partial-indistinguishability. This notion is based
on computationally universal groups with efficiently computable normal forms,
and appears to be incomparable with existing definitions. We describe universal
gate sets for both classical and quantum computation, in which our definition
of obfuscation can be met by polynomial-time algorithms. We also discuss some
potential applications to testing quantum computers. We stress that the
cryptographic security of these obfuscators, especially when composed with
translation from other gate sets, remains an open question.Comment: 21 pages,Proceedings of TQC 201
The role of noise in sensorimotor control
Goal-directed arm movements show stereotypical trajectories, despite the infinite possible ways to reach a given end point. This thesis examines the hypothesis that this stereotypy arises because movements are optimised to reduce the consequences of signal-dependent noise on the motor command. Both experimental and modelling studies demonstrate that signal-dependent noise arises from the normal behaviour of the muscle and motor neuron pool, and has a particular distribution across muscles of different sizes. Specifically, noise decreases in a systematic fashion with increasing muscle strength and motor unit number. Simulations of obstacle avoidance performance in the presence of signal-dependent noise demonstrate that the optimal trajectory for reaching the target accurately and without collision matches the observed trajectories. Isometric force generation is also shown to have systematic changes in variability with posture, which can be explained by the presence of signal-dependent noise in the muscles of the arm. These results confirm the tested hypothesis and imply that consideration of the statistics of action is crucial to human movement planning. To investigate the importance of feedback in the motor system, the impact of static position on motor excitability was examined using transcranial magnetic stimulation and systematic changes in motor evoked potentials were observed. Force generated at the wrist following stimulation was analysed in terms of different possible movement representations, and the differences between force fields arising from stimulation over the cervical spinal cord and from stimulation over primary motor cortex are determined. These results demonstrate the structured influence of proprioceptive feedback on the human motor system. All the experiments are discussed in relation to current theories describing the control of human movements and the impact of noise in the motor system
Nucleation barrier reconstruction via the seeding method in a lattice model with competing nucleation pathways
We study a three-species analogue of the Potts lattice gas model of nucleation from solution in a regime where partially disordered solute is a viable thermodynamic phase. Using a multicanonical sampling protocol, we compute phase diagrams for the system, from which we determine a parameter regime where the partially disordered phase is metastable almost everywhere in the temperatureâfugacity plane. The resulting model shows non-trivial nucleation and growth behaviour, which we examine via multidimensional free energy calculations. We consider the applicability of the model in capturing the multi-stage nucleation mechanisms of polymorphic biominerals (e.g., CaCO3). We then quantitatively explore the kinetics of nucleation in our model using the increasingly popular âseedingâ method. We compare the resulting free energy barrier heights to those obtained via explicit free energy calculations over a wide range of temperatures and fugacities, carefully considering the propagation of statistical error. We find that the ability of the âseedingâ method to reproduce accurate
free energy barriers is dependent on the degree of supersaturation, and severely limited by the use of a nucleation driving force â” computed for bulk phases. We discuss possible reasons for this in terms of underlying kinetic assumptions, and those of classical nucleation theory. C 2016 Author(s
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