A Stochastic Model of Plausibility in Live-Virtual-Constructive Environments

Distributed live-virtual-constructive simulation promises a number of benefits for the test and evaluation community, including reduced costs, access to simulations of limited availability assets, the ability to conduct large-scale multi-service test events, and recapitalization of existing simulation investments. However, geographically distributed systems are subject to fundamental state consistency limitations that make assessing the data quality of live-virtual-constructive experiments difficult. This research presents a data quality model based on the notion of plausible interaction outcomes. This model explicitly accounts for the lack of absolute state consistency in distributed real-time systems and offers system designers a means of estimating data quality and fitness for purpose. Experiments with World of Warcraft player trace data validate the plausibility model and exceedance probability estimates. Additional experiments with synthetic data illustrate the model\u27s use in ensuring fitness for purpose of live-virtual-constructive simulations and estimating the quality of data obtained from live-virtual-constructive experiments

Dealing with the Effect of Path Curvature on Consistency of Dead Reckoned Paths in Networked Virtual Environments

Several techniques exist which reduce network bandwidth consumption and thus limit the effects of network latency in networked virtual environments. Dead reckoning is one such technique that has been widely adopted for use with dynamic entities. However, in previous work we have shown that the use of a spatial threshold alone in dead reckoning can result in unbounded absolute inconsistency. A novel hybrid threshold was proposed that combined a spatial threshold together with an absolute consistency metric to impose an upper bound on absolute inconsistency under all circumstances. This was verified through a simulation of typical movement in a computer racing game. This paper extends this work by investigating the problem in more detail and verifying the hybrid threshold solution in live trials across the Internet. In particular the relationship between curvature of movement and absolute consistency is explored. The experimental trials allow a comparative analysis of how users behave when different threshold types are used under varying degrees of curvature. This work provides further justification for the use of a hybrid threshold approach when dead reckoning is employed in networked virtual environments

Formalizing a Framework for Dynamic Hybrid Strategy Models in Distributed Interactive Applications

Predictive contract mechanisms such as dead reckoning are widely employed to support scalable remote entity modelling in Distributed Interactive Applications (DIAs). By employing a form of controlled inconsistency, a reduction in network traffic is achieved. Previously, we have proposed the Dynamic Hybrid Strategy Model (DHSM) as an extension to the concept of dead reckoning that adaptively selects extrapolation models based on the use of local performance criteria. In this paper, we formalize the notion of the DHSM as a generalized framework for network traffic reduction in DIAs, alongside a set of consistency metrics for use as local performance criteria

On Consistency and Network Latency in Distributed Interactive Applications: A Survey—Part I

This paper is the first part of a two-part paper that documents a detailed survey of the research carried out on consistency and latency in distributed interactive applications (DIAs) in recent decades. Part I reviews the terminology associated with DIAs and offers definitions for consistency and latency. Related issues such as jitter and fidelity are also discussed. Furthermore, the various consistency maintenance mechanisms that researchers have used to improve consistency and reduce latency effects are considered. These mechanisms are grouped into one of three categories, namely time management, Information management and system architectural management. This paper presents the techniques associated with the time management category. Examples of such mechanisms include time warp, lock step synchronisation and predictive time management. The remaining two categories are presented in part two of the survey

Exploring the Effect of Curvature on the Consistency of Dead Reckoned Paths for Different Error Threshold Metrics

Dead reckoning is widely employed as an entity update packet reduction technique in Distributed Interactive Applications (DIAs). Such techniques reduce network bandwidth consumption and thus limit the effects of network latency on the consistency of networked simulations. A key component of the dead reckoning method is the underlying error threshold metric, as this directly determines when an entity update packet is to be sent between local and remote users. The most common metric is the spatial threshold, which is simply based on the distance between a local user’s actual position and their predicted position. Other, recently proposed, metrics include the time-space threshold and the hybrid threshold, both of which are summarised within. This paper investigates the issue of user movement in relation to dead reckoning and each of the threshold metrics. In particular the relationship between the curvature of movement, the various threshold metrics and absolute consistency is studied. Experimental live trials across the Internet allow a comparative analysis of how users behave when different threshold metrics are used with varying degrees of curvature. The presented results provide justification for the use of a hybrid threshold approach when dead reckoning is employed in DIAs

Examining the Effects of Time-Space Measures on the Hybrid Strategy Model in Networked Virtual Environments

Scalability is an important issue in the design of networked virtual environments (NVEs). In order to achieve scalability, it is essential to minimise the network traffic required to maintain overall consistency in the NVE. A popular method of achieving this is via entity behaviour prediction mechanisms, such as dead reckoning and the hybrid strategy model (HSM). Typically, the performance of such mechanisms is rated by the number of network packets they generate. However, it is also important that their impact on overall consistency is investigated. Absolute consistency is the degree to which different views of a NVE on remote hosts correspond. In previous work, it was shown that the use of a spatial threshold with dead reckoning can result in unbounded local absolute consistency. A solution that employed a time-space error threshold measure was shown to remedy this issue. In this paper, the scope of the time-space measure is extended to include the HSM. It is shown how the HSM can also result in unbounded local absolute inconsistency. A solution that once again incorporates the time-space threshold is examined. However, this approach results in a significant increase in network traffic. To resolve this, a novel extension to the HSM algorithm is presented, which is demonstrated to reduce network traffic, whilst still maintaining a low level of local absolute inconsistency

Network traffic analysis and evaluation of a multi-user virtual environment

Virtual world applications allow users to interact within a simulated world. Network responsiveness and reliability contribute to the user experience, thus being able to model and reproduce certain network scenarios is a key issue to assure proper user experience and for being able to provide an estimation of the required network resources. The present study aims to model the client network traffic for the virtual world application Open Wonderland as the basis to tools for evaluating its network requirements. A micro scale modelling was performed, studying the outgoing network traffic from a black box approach that omits the details of traffic generation of the subcomponents and focuses on their overall combined traffic. The model obtained provides high goodness of fit for audio and object synchronisation traffic, reflected in a Pearson correlation coefficient close to its maximum value and low deviation figures measured by Root Mean Square Deviation.Ministerio de Ciencia e innovación IPT-2011-1038-900000Ministerio de Ciencia e innovación TEC2009-10639-C04-0