Paul Boustead

Managing latency and fairness in networked games

Fighting propagation delays in real-time interactive applications improves gameplay and fairness in networked games by trading off inconstencies and tuning decision points topology.

Optimal assignment of distributed servers to virtual partitionsfor the provision of immersive voice communicationin massively multiplayer games

This paper investigates the assignment of audio mixing operations to a geographically distributed set of servers to provide an immersive voice communication environment for massively multi-player online games. The immersive voice communication service enables each avatar to hear a spatially accurate audio mix of the conversations in its hearing range. There are three primary delivery architectures for this service, namely, peer-to-peer, central server, and distributed servers. We focus on a distributed server architecture, which partitions the virtual world into regions or locales and then assigns the computation associated with the creation of audio scenes for all avatars in each locale to a server. Our aim is to find the optimal way to partition the virtual world into locales and then choose the locale servers in such a way that reduces the total delay perceived by all avatars. We have produced a mathematical formulation for the optimal partitioning and server assignment and developed a heuristics approach based on a graph algorithm. We have developed a simulation environment that creates both the physical world (geographic distribution of participants and the Internet topology model) and the virtual world (distribution of avatars based on different avatar aggregation behaviors). We have solved the problem exactly as well as using the heuristics for a range of simulated virtual and physical worlds. In many cases, the heuristics results were within 5% of the optimal. Our algorithms and simulation study will be of benefit to future immersive voice communication service providers in the design of a cost effective delivery architecture for this service.

Comparison of delivery architectures for immersive audio in crowded networked games

This paper examines appropriate network and server infrastructures for the provision of a realistic audio scene from the perspective of avatars in large-scale virtual environments. The audio scene of each avatar combines the voices and other sources of sound in the vicinity of the avatar, spatially placed, attenuated according to distance from the listener, and addition of sound effects to reflect the acoustic characteristics of the environment. We examine a range of delivery options including central-server, peer-to-peer with and without multicast, distributed proxies, distributed locale servers, and a hybrid model. We provide numerical results on the effect of different virtual world characteristics such as avatar density, hearing range, and correlation between the positions in the virtual and physical worlds. We compare delivery architectures based on a set of delay metrics aimed at measuring the interactive delay between avatars as well as accuracy of the scene. We make several recommendations on scalable implementation of such applications.

Reliable optimised flooding in ad hoc networks

Information dissemination (flooding) forms an integral part of routing protocols, network management, service discovery and information collection (sensing). Given the broadcast nature of ad hoc network communications, information dissemination provides a challenging problem. Blind flooding in ad hoc networks results in the broadcast storm problem. To limit the broadcast storm problem, mechanisms for optimised flooding have been proposed. However, this optimisation reduces the inherent level of redundancy. the minimum spanning tree (MST) algorithm using local one hop topology in a distributed manner as the basis of a more reliable optimised flooding mechanism called, reliable minimum spanning tree (RMST) flood is proposed. RMST utilises unique properties of MST graphs that allow for broadcast transmissions to be replaced by unicast transmissions. Unicast transmission is inherently more reliable than broadcast transmission as it utilises link layer acknowledgement and retransmission, thereby improving the reliability of a flood and reducing the broadcast storm problem. Simulation is used to show that RMST is able to achieve equivalent reliability in terms of packet delivery compared to blind flooding. Importantly, RMST is able to achieve significantly better performance than MPR and equivalent performance to LMSTFlood in terms of reducing the broadcast storm problem.

DICE: Internet delivery of immersive voice communication for crowded virtual spaces

This paper develops a scalable system design for the creation, and delivery over the Internet, of a realistic voice communication service for crowded virtual spaces. Examples of crowded spaces include virtual market places or battlefields in online games. A realistic crowded audio scene including spatial rendering of the voices of surrounding avatars is impractical to deliver over the Internet in a peer-to-peer manner due to access bandwidth limitations and cost. A brute force server model, on the other hand, will face significant computational costs and scalability issues. This paper presents a novel server-based architecture for this service that performs simple operations in the servers (including weighted mixing of audio streams) to cope with access bandwidth restrictions of clients, and uses spatial audio rendering capabilities of the clients to reduce the computational load on the servers. This paper then examines the performance of two components of this architecture: angular clustering and grid summarization. The impact of two factors, namely a high density of avatars and realistic access bandwidth limitations, on the quality and accuracy of the audio scene is then evaluated using simulation results.

Fairness and playability in online multiplayer games

Playability and fairness are crucial elements of an enjoyable online game experience. The unavoidable propagation time introduced by the geographical distance between partici- pants can deteriorate the game responsiveness and playability. Also, differences in these delays can provide unfair advantages and/or disadvantages to different players. This paper explores the causal relationships between prop- agation time, inconsistencies, playability and fairness in on- line multiplayer games. It clearly defines causes of unfairness and introduces a theoretical quantification supported by an experimental technique to evaluate it in simulations. It also demonstrates through simulations the impact of changes in network architecture and topology on playability and fairness. I. INTRODUCTION

Provisioning overlay distribution networks

Future entertainment services are expected to be increasingly interactive, on demand and personalized. This paper aims to address the challenge of provisioning network and server resources to support the distribution of these services over the Internet. We propose the Overlay Distribution Network (ODN) as a cost-effective means to deliver these services. Because ODNs are created over shared network and server infrastructure, the provisioning problem becomes significantly complex. The paper formulates this problem as a joint resource provisioning and content replication optimization. The resulting formulation is proved to be NP-complete. We solved this problem with an efficient Lagrangian heuristic. Further, content clustering is employed to improve the heuristic run time. Initial results show that this is efficient. In some cases, clustering allows solutions with very similar quality to be achieved at a 20 times reduction in complexity.

Resource aware information dissemination in ad hoc networks

Information dissemination (flooding) forms an integral part of routing protocols, network management, service discovery and information collection (sensing). Given the broadcast nature of ad hoc network communications, information dissemination provides a challenging problem. This paper introduces Utility Based Flooding (UBF). UBF is a distributed optimised flooding mechanism for ad hoc networks that unlike existing optimised flooding algorithms is fully resource aware. Resource awareness is achieved by assigning a forwarding utility to neighouring nodes to determining the desirability of a neighbouring node in continuing a flood. UBF is particularly applicable to ad hoc network environments composed of heterogeneous nodes that may have varying characteristics and constraints. In this paper, UBF is compared to existing flooding mechanism in a constrained environment. Nodes are assigned varying degrees of remaining battery power and user based constraints that limit a nodes benevolence based upon its remaining battery power. We show through simulation that UBF compared to Utility Based Multipoint Relay (UMPR) flooding, Multipoint Relay (MPR) flooding and Blind flooding significantly improves broadcast reachability over successive broadcasts, does not adversely affect performance and extends the lifetime of the network. UBF delivers packets to over 90% of nodes in the network for over 70 successive broadcasts. Blind flooding, UMPR and MPR are only able achieve 42, 39 and 23 successive broadcasts respectively. Disciplines Physical Sciences and Mathematics Publication Details This article was originally published as: Lipman, J, Boustead, P, Chicharo, J & Judge, J, Resource aware information dissemination in ad hoc networks, The 11th IEEE International Conference on Networks (ICON2003), 28 September-1 October 2003, 591-596. Copyright IEEE 2003. This conference paper is available at Research Online: http://ro.uow.edu.au/infopapers/194 Resource Aware Information Dissemination in Ad hoc Networks Justin Lipman and Paul Boustead and Joe Chicharo Telecommunications and Information Technology Research Institute University of Wollongong Email: {justin,paul,joexhicharo}@titr.uow.edu.au John Judge Motorola Australian Research Centre 12 Lord Street, Botany, NSW, Australia Wollongong Australia Email john.judge@motorola.com AbsPacIInformation dissemination (flooding) forms an in tegral part of routing protocols, network management, semce discovery and information collection (sensing). Given the broad cast nature of ad hoc network communications, information dissemination provides a challenging problem. This paper in trodnces Utility Based Flooding (UBF). UBF is a distributed optimised flooding mechanism for ad hoc networks that unlike existing optimised flooding algorithms is fnUy resource aware. Resource awareness is achieved by assigning a forwarding utility to neighouring nodes to determining the desirability of a neigh honring node in continuing a flood. UBF is particularly applicable to ad hoc network environments composed of heterogeneous nodm that may have varying characteristics and constraints. In this paper, UBF is compared to existing flooding mechanism in a constrained environment. Nodes are assigned varying degrees of remaining battery power and user based constraints that limit a nodes benevolence based upon its remaining battery power. We show through simulation that UBF compared to Utility Based Multipoint Relay (UMPR) flooding, Multipoint Relay (MPR) flooding and Blind flooding significantly improves broadcast reachability over successive broadcasts, does not adversely atfeet performance and extends the lifetime of the network. UBF delivers packets to over 90% of nodes in the network for over 70 successive broadcasts. Blind flooding, UMPR and MPR are only able achieve 42, 39 and 23 successive broadcasts respectively.

A hybrid optical network architecture consisting of optical cross connects and optical burst switches

Optical burst switches (OBSes) have been proposed to improve the utilization of a network of optical cross connect (OXCs). Current studies on OBS assume a network consisting of OBSes alone. While this is a reasonable assumption for evaluating a new technology, the question of how a network of OXCs can be evolved to a network of OBSes has not been studied. In this paper, we propose a hybrid architecture consisting of OBSes at the network edge and OXCs in the network core. This architecture allows carriers to gradually migrate from an OXC-based network to an OBS-based network with an improved network utilization. In addition, we use queueing analysis to study the performance of this new architecture.

NEIGHBOR AWARE ADAPTIVE POWER FLOODING (NAAP) IN MOBILE AD HOC NETWORKS

This paper introduces Neighbor Aware Adaptive Power flooding, an optimized flooding mechanism used in mobile ad hoc networks (MANETS) that employs several mechanisms (neighbor coverage, power control, neighbor awareness and local optimization) to limit the broadcast storm problem, reduce duplicate packet reception and lower power consumption in both transmission and reception. Upon receiving an optimized broadcast, a relay determines a new set of possible relays (to continue the flood) based upon local neighbor information and the previous optimized broadcast. Additionally, neighboring relays only consider the shared neighbors they are closest to. A relay may perform local optimization (to reduce power consumption and isolate broadcasts) by substituting one high power broadcast with two or more low power broadcasts, thereby introducing additional hops, We show that compared to blind flooding and multipoint relaying, NAAP in a static environment greatly reduces the problems associated with the broadcast storm problem, duplicate packet reception and power consumption.