ptp++: A Precision Time Protocol Simulation Model for OMNeT++ / INET

Precise time synchronization is expected to play a key role in emerging distributed and real-time applications such as the smart grid and Internet of Things (IoT) based applications. The Precision Time Protocol (PTP) is currently viewed as one of the main synchronization solutions over a packet-switched network, which supports microsecond synchronization accuracy. In this paper, we present a PTP simulation model for OMNeT++ INET, which allows to investigate the synchronization accuracy under different network configurations and conditions. To show some illustrative simulation results using the developed module, we investigate on the network load fluctuations and their impacts on the PTP performance by considering a network with class-based quality-of-service (QoS) support. The simulation results show that the network load significantly affects the network delay symmetry, and investigate a new technique called class probing to improve the PTP accuracy and mitigate the load fluctuation effects.Comment: Published in: A. F\"orster, C. Minkenberg, G. R. Herrera, M. Kirsche (Eds.), Proc. of the 2nd OMNeT++ Community Summit, IBM Research - Zurich, Switzerland, September 3-4, 201

The face inhibition effect: Social contrast or motor competition?

Merely viewing the faces of famous athletes affects the observers' motor system, suggesting that actionbased information is a core feature of person representations, even when no specific action is visible (Bach & Tipper, 2006). Unexpectedly, these person-based motor priming effects were inhibitory. Foot responses were slower when identifying footballers, and hand responses for tennis players. Here, we demonstrate that these inhibitory effects are only evoked when action is implicitly associated with the athletes; when the athletes are seen performing their skilled actions the effect reverses towards facilitation. The contrast between inhibition evoked by implicit action priming and facilitation evoked by the explicit presentation of an action supports the notion of inhibitory control in the motor system. We hypothesise that when no specific action is perceived, a range of actions are activated triggering lateral inhibition, whereas when a specific action is viewed, there is no competition and excitation facilitates similar responses. © 2011 Psychology Press

Simple and Robust Boolean Operations for Triangulated Surfaces

Boolean operations of geometric models is an essential issue in computational geometry. In this paper, we develop a simple and robust approach to perform Boolean operations on closed and open triangulated surfaces. Our method mainly has two stages: (1) We firstly find out candidate intersected-triangles pairs based on Octree and then compute the inter-section lines for all pairs of triangles with parallel algorithm; (2) We form closed or open intersection-loops, sub-surfaces and sub-blocks quite robustly only according to the cleared and updated topology of meshes while without coordinate computations for geometric enti-ties. A novel technique instead of inside/outside classification is also proposed to distinguish the resulting union, subtraction and intersection. Several examples have been given to illus-trate the effectiveness of our approach.Comment: Novel method for determining Union, Subtraction and Intersectio

Spare capacity allocation using shared backup path protection for dual link failures

This paper extends the spare capacity allocation (SCA) problem from single link failure [1] to dual link failures on mesh-like IP or WDM networks. The SCA problem pre-plans traffic flows with mutually disjoint one working and two backup paths using the shared backup path protection (SBPP) scheme. The aggregated spare provision matrix (SPM) is used to capture the spare capacity sharing for dual link failures. Comparing to a previous work by He and Somani [2], this method has better scalability and flexibility. The SCA problem is formulated in a non-linear integer programming model and partitioned into two sequential linear sub-models: one finds all primary backup paths first, and the other finds all secondary backup paths next. The results on five networks show that the network redundancy using dedicated 1+1+1 is in the range of 313-400%. It drops to 96-181% in 1:1:1 without loss of dual-link resiliency, but with the trade-off of using the complicated share capacity sharing among backup paths. The hybrid 1+1:1 provides intermediate redundancy ratio at 187-310% with a moderate complexity. We also compare the passive/active approaches which consider spare capacity sharing after/during the backup path routing process. The active sharing approaches always achieve lower redundancy values than the passive ones. These reduction percentages are about 12% for 1+1:1 and 25% for 1:1:1 respectively

Cell sleeping for energy efficiency in cellular networks: Is it viable?

An approach advocated in the recent literature for reducing energy consumption in cellular networks is to put base stations to sleep when traffic loads are low. However, several practical considerations are ignored in these studies. In this paper, we aim to raise questions on the feasibility and benefits of base station sleeping. Specifically we analyze the interference and capacity of a coverage-based energy reduction system in CDMA based cellular networks using a simple analytical model and show that sleeping may not be a feasible solution to reduce energy consumption in many scenarios. © 2012 IEEE

Focusing on body sites: the role of spatial attention in action perception.

Humans use the same representations to code self-produced and observed actions. Neurophysiological evidence for this view comes from the discovery of the so-called mirror neurons in premotor cortex of the macaque monkey. These neurons respond when the monkey performs a particular action but also when it observes the same behavior in another individual. In humans, such direct links between perception and action seem to mediate action priming, where a response is facilitated when a similar action is observed. An issue that has not been fully resolved concerns the role of selective attention in these processes. Action priming appears to be an automatic process in the sense that the observed action can be irrelevant to the observer's task and nevertheless prime similar responses. However, it is not known whether attention has to be oriented to the action for these processes to be engaged. It is demonstrated here that spatial attention indeed has to be oriented to the action related body site for action priming to take place. Furthermore, if attention is oriented to the appropriate body site, there need be no visual cues to action for action priming to emerge

Information reuse in dynamic spectrum access

Dynamic spectrum access (DSA), where the permission to use slices of radio spectrum is dynamically shifted (in time an in different geographical areas) across various communications services and applications, has been an area of interest from technical and public policy perspectives over the last decade. The underlying belief is that this will increase spectrum utilization, especially since many spectrum bands are relatively unused, ultimately leading to the creation of new and innovative services that exploit the increase in spectrum availability. Determining whether a slice of spectrum, allocated or licensed to a primary user, is available for use by a secondary user at a certain time and in a certain geographic area is a challenging task. This requires 'context information' which is critical to the operation of DSA. Such context information can be obtained in several ways, with different costs, and different quality/usefulness of the information. In this paper, we describe the challenges in obtaining this context information, the potential for the integration of various sources of context information, and the potential for reuse of such information for related and unrelated purposes such as localization and enforcement of spectrum sharing. Since some of the infrastructure for obtaining finegrained context information is likely to be expensive, the reuse of this infrastructure/information and integration of information from less expensive sources are likely to be essential for the economical and technological viability of DSA. © 2013 IEEE