Jan Sablatnig

Scalability of a distributed virtual environment based on a structured peer-to-peer architecture

We investigate the scalability of distributed virtual environments (DVEs) based on a structured peer-to-peer (P2P) overlay. We focus on network load and message routing latency. To this end, we study a prototypical DVE consisting of a simple game scenario and a P2P architecture based on Pastry and Scribe as proposed by Knutsson et al. [1]. Both our theoretical analysis and simulation results show that under constant population density, the network load is constant except for the overhead messages incurred by the overlay protocol. The overall network load per host as well as the message routing latency grows logarithmically with the number of hosts; this is in partial contradiction to Knutsson et al.s results. We propose a resolution to this contradiction.

Adam A Testbed for Distributed Virtual Environments

In distributed virtual environments (DVEs) the data on which the hosts operate is not consistent at all times. To restore data consistency, the DVE has to employ a consistency algorithm. Unfortunately, all existing DVEs have been built for specific application scenarios, which makes it impossible to compare the consistency algorithms and to choose a suitable candidate for a new scenario. To overcome this, we have created a modular simulator-based DVE testbed named Adam with the ability to plug in different application scenarios as well as different consistency algorithms and network constraints. The testbed also contains a large set of measurement tools. Our testbed currently supports two application scenarios and several of the most common consistency algorithms found in the literature. We can compare the solutions on an objective scale and confirm that optimistic consistency typically outperforms loose consistency.

Surveillance and Datenschutz in Virtual Environments

Virtual environments are becoming more and more accepted, and part of the everyday online experience for many users. This offers new potential for both surveillance and data mining. Some of the techniques used are discussed in this paper.

Dealing with Multiple Truths in Online Virtual Worlds

Virtual environments and online games are becoming a major market force. At the same time, the virtual property contained in these environments is being traded for real money and thus attains a real value. Although the legal issues involved with this virtual property have not yet been decided, they will have to be soon. It is foreseeable that the next generation of very large virtual worlds will carry the possibility of multiple truths existing at the same time. Under such circumstances, it will be impossible to physically protect virtual property. In order to protect virtual property, virtual environment systems will therefore have to conform to certain requirements. We analyze what these requirements are in order to either prevent cheating or at least prove a digital offence has transpired. Along with greater security, this will also simplify end user support, which is one of the major cost factors for online games. [Article copies are available for purchase from InfoSci-on-Demand.com]

High-bitrate approximation

We are reviewing scalar quantizers with deadzone and overload in the high-bitrate approximation, give sharp bounds on the quality of this approximation and present results on the optimal quantizer in this setting. Some recent results by Hui and Neuhoff are reproduced under weaker conditions. We conclude by comparing the mathematical results with experimental data. For details about the results of this article we refer to an article in prepeparation.