Simulation of Area of Interest Management for Massively Multiplayer Online Games Using OPNET

In recent years, there has been an important growth of online gaming. Today’s Massively Multiplayer Online Games (MMOGs) can contain millions of synchronous players scattered across the world and participating with each other within a single shared game. The increase in the number of players in MMOGs has led to some issues with the demand of server which generates a significant increase in costs for the game industry and impacts to the quality of service offered to players. With the number of players gradually increasing, servers still need to work efficiently under heavy load and, new researches are required to improve the established MMOG system architectures. In dealing with a considerable scale of massively multiplayer online games, several client-server and peer-to-peer solutions have been proposed. Although they have improved the scalability of MMOGs in different degrees, they faced new serious challenges in interest management. In this paper, we propose a novel static area of interest management in order to reduce the delay and traffic of Hybrid P2P MMOGs. We propose to use OPNET Modeler 18.0, and in particular the custom application to simulate the new architecture, which required the implementation of new nodes models and behaviors in the simulator to emulate correctly the new architecture. The scenarios include both client-server and hybrid P2P system to evaluate the communication of games with (125, 500, and 1000) peers. The simulation results show that area of interest management for MMOGs based on the hybrid P2P architectures have low delay and traffic received compared with MMOGs based on client-server system

Dynamic Load Balancing for Massively Multiplayer Online Games Using OPNET

In recent years, there has been an important growth of online gaming. Today’s Massively Multiplayer Online Games (MMOGs) can contain millions of synchronous players scattered across the world and participating with each other within a single shared game. Traditional Client/Server architectures of MMOGs exhibit different problems in scalability, reliability, and latency, as well as the cost of adding new servers when demand is too high. P2P architecture provides considerable support for scalability of MMOGs. It also achieves good response times by supporting direct connections between players. In this paper, we have proposed a novel dynamic load balancing for massively multiplayer online games (MMOGs) based this hybrid Peer-to-Peer architecture. We have divided the game world space into several regions. Each region in the game world space is controlled and managed by using both a super-peer and a clone-super-peer. The region's super-peer is responsible for distributing the game update among the players inside the region, as well as managing the game communications between the players. However, the clone-super-peer is responsible for controlling the players' migration from one region to another, in addition to be the super-peer of the region when the super-peer leaves the game. We have designed and evaluated the dynamic load balancing for MMOGs based on hybrid P2P architecture. We have used OPNET Modeler 18.0 to simulate and evaluate the proposed system. Our dynamic load balancer is responsible for distributing the load among the regions in the game world space. The position of the load balancer is located between the game server and the regions. The results, following extensive experiments, show that low delay and higher traffic communication can be achieved using dynamic load balancing for MMOGs based on hybrid P2P system

Dynamic Load Balancing for Massively Multiplayer Online Games

In recent years, there has been an important growth of online gaming. Today’s Massively Multiplayer Online Games (MMOGs) can contain millions of synchronous players scattered across the world and participating with each other within a single shared game. Traditional Client/Server architectures of MMOGs exhibit different problems in scalability, reliability, and latency, as well as the cost of adding new servers when demand is too high. P2P architecture provides considerable support for scalability of MMOGs. It also achieves good response times by supporting direct connections between players. This thesis proposes a novel hybrid Peer-to-Peer architecture for MMOGs and a new dynamic load balancing for massively multiplayer online games (MMOGs) based this hybrid Peer-to-Peer architecture. We have divided the game world space into several regions. Each region in the game world space is controlled and managed by using both a super-peer and a clone-super-peer. The region's super-peer is responsible for distributing the game update among the players inside the region, as well as managing the game communications between the players. However, the clone-super-peer is responsible for controlling the players' migration from one region to another, in addition to be the super-peer of the region when the super-peer leaves the game. In this thesis, we have designed and simulated a static and dynamic Area of Interest Management (AoIM) for MMOGs based on both architectures hybrid P2P and client-server with the possibility of players to move from one region to another. In this thesis also, we have designed and evaluated the static and dynamic load balancing for MMOGs based on hybrid P2P architecture. We have used OPNET Modeler 18.0 to simulate and evaluate the proposed system, especially standard applications, custom applications, TDMA and RX Group. Our dynamic load balancer is responsible for distributing the load among the regions in the game world space. The position of the load balancer is located between the game server and the regions. The results, following extensive experiments, show that low delay and higher traffic communication can be achieved using both of hybrid P2P architecture, static and dynamic AoIM, dynamic load balancing for MMOGs based on hybrid P2P system

Heuristics for Client Assignment and Load Balancing Problems in Online Games

Massively multiplayer online games (MMOGs) have been very popular over the past decade. The infrastructure necessary to support a large number of players simultaneously playing these games raises interesting problems to solve. Since the computations involved in solving those problems need to be done while the game is being played, they should not be so expensive that they cause any noticeable slowdown, as this would lead to a poor player perception of the game. Many of the problems in MMOGs are NP-Hard or NP-Complete, therefore we must develop heuristics for those problems without negatively affecting the player experience as a result of excessive computation. In this dissertation, we focus on a few of the problems encountered in MMOGs – the Client Assignment Problem (CAP) and both centralized and distributed load balancing – and develop heuristics for each. For the CAP we investigate how best to assign players to servers while meeting several conditions for satisfactory play, while in load balancing we investigate how best to distribute load among game servers subject to several criteria. In particular, we develop three heuristics - a heuristic for a variant of the CAP called Offline CAP-Z, a heuristic for centralized load balancing called BreakpointLB, and a heuristic for distributed load balancing called PLGR. We develop a simulator to simulate the operations of an MMOG and implement our heuristics to measure performance against adapted heuristics from the literature. We find that in many cases we are able to produce better results than those adapted heuristics, showing promise for implementation into production environments. Further, we believe that these ideas could also be easily adapted to the numerous other problems to solve in MMOGs, and they merit further consideration and augmentation for future research

Passage à l'échelle pour les mondes virtuels

Virtual worlds attract millions of users and these popular applications --supported by gigantic data centers with myriads of processors-- are routinely accessed. However, surprisingly, virtual worlds are still unable to host simultaneously more than a few hundred users in the same contiguous space.The main contribution of the thesis is Kiwano, a distributed system enabling an unlimited number of avatars to simultaneously evolve and interact in a contiguous virtual space. In Kiwano we employ the Delaunay triangulation to provide each avatar with a constant number of neighbors independently of their density or distribution. The avatar-to-avatar interactions and related computations are then bounded, allowing the system to scale. The load is constantly balanced among Kiwano's nodes which adapt and take in charge sets of avatars according to their geographic proximity. The optimal number of avatars per CPU and the performances of our system have been evaluated simulating tens of thousands of avatars connecting to a Kiwano instance running across several data centers, with results well beyond the current state-of-the-art.We also propose Kwery, a distributed spatial index capable to scale dynamic objects of virtual worlds. Kwery performs efficient reverse geolocation queries on large numbers of moving objects updating their position at arbitrary high frequencies. We use a distributed spatial index on top of a self-adaptive tree structure. Each node of the system hosts and answers queries on a group of objects in a zone, which is the minimal axis-aligned rectangle. They are chosen based on their proximity and the load of the node. Spatial queries are then answered only by the nodes with meaningful zones, that is, where the node's zone intersects the query zone.Kiwano has been successfully implemented for HybridEarth, a mixed reality world, Manycraft, our scalable multiplayer Minecraft map, and discussed for OneSim, a distributed Second Life architecture. By handling avatars separately, we show interoperability between these virtual worlds.With Kiwano and Kwery we provide the first massively distributed and self-adaptive solutions for virtual worlds suitable to run in the cloud. The results, in terms of number of avatars per CPU, exceed by orders of magnitude the performances of current state-of-the-art implementations. This indicates Kiwano to be a cost effective solution for the industry. The open API for our first implementation is available at \url{http://kiwano.li}.La réalité mixe, les jeux en ligne massivement multijoueur (MMOGs), les mondes virtuels et le cyberespace sont des concepts extrêmement attractifs. Mais leur déploiement à large échelle reste difficile et il est en conséquence souvent évité.La contribution principale de la thèse réside dans le système distribué Kiwano, qui permet à un nombre illimité d'avatars de peupler et d'interagir simultanément dans un même monde contigu. Dans Kiwano nous utilisons la triangulation de Delaunay pour fournir à chaque avatar un nombre constant de voisins en moyenne, indépendamment de leur densité ou distribution géographique. Le nombre d'interactions entre les avatars et les calculs inhérents sont bornés, ce qui permet le passage à l'échelle du système.La charge est repartie sur plusieurs machines qui regroupent sur un même nœud les avatars voisins de façon contiguë dans le graphe de Delaunay. L'équilibrage de la charge se fait de manière contiguë et dynamique, en suivant la philosophie des réseaux pair-à-pair (peer-to-peer overlays). Cependant ce principe est adapté au contexte de l'informatique dématérialisée (cloud computing).Le nombre optimal d'avatars par CPU et les performances de notre système ont été évalués en simulant des dizaines de milliers d'avatars connectés à la même instance de Kiwano tournant à travers plusieurs centres de traitement de données.Nous proposons également trois applications concrètes qui utilisent Kiwano : Manycraft est une architecture distribuée capable de supporter un nombre arbitrairement grand d'utilisateurs cohabitant dans le même espace Minecraft, OneSim, qui permet à un nombre illimité d'usagers d'être ensemble dans la même région de Second Life et HybridEarth, un monde en réalité mixte où avatars et personnes physiques sont présents et interagissent dans un même espace: la Terre

Virtual Reality Games for Motor Rehabilitation

This paper presents a fuzzy logic based method to track user satisfaction without the need for devices to monitor users physiological conditions. User satisfaction is the key to any product’s acceptance; computer applications and video games provide a unique opportunity to provide a tailored environment for each user to better suit their needs. We have implemented a non-adaptive fuzzy logic model of emotion, based on the emotional component of the Fuzzy Logic Adaptive Model of Emotion (FLAME) proposed by El-Nasr, to estimate player emotion in UnrealTournament 2004. In this paper we describe the implementation of this system and present the results of one of several play tests. Our research contradicts the current literature that suggests physiological measurements are needed. We show that it is possible to use a software only method to estimate user emotion

Referee-based architectures for massively multiplayer online games

Network computer games are played amongst players on different hosts across the Internet. Massively Multiplayer Online Games (MMOG) are network games in which thousands of players participate simultaneously in each instance of the virtual world. Current commercial MMOG use a Client/Server (C/S) architecture in which the server simulates and validates the game, and notifies players about the current game state. While C/S is very popular, it has several limitations: (i) C/S has poor scalability as the server is a bandwidth and processing bottleneck; (ii) all updates must be routed through the server, reducing responsiveness; (iii) players with lower client-to-server delay than their opponents have an unfair advantage as they can respond to game events faster; and (iv) the server is a single point of failure.The Mirrored Server (MS) architecture uses multiple mirrored servers connected via a private network. MS achieves better scalability, responsiveness, fairness, and reliability than C/S; however, as updates are still routed through the mirrored servers the problems are not eliminated. P2P network game architectures allow players to exchange updates directly, maximising scalability, responsiveness, and fairness, while removing the single point of failure. However, P2P games are vulnerable to cheating. Several P2P architectures have been proposed to detect and/or prevent game cheating. Nevertheless, they only address a subset of cheating methods. Further, these solutions require costly distributed validation algorithms that increase game delay and bandwidth, and prevent players with high latency from participating.In this thesis we propose a new cheat classification that reflects the levels in which the cheats occur: game, application, protocol, or infrastructure. We also propose three network game architectures: the Referee Anti-Cheat Scheme (RACS), the Mirrored Referee Anti-Cheat Scheme (MRACS), and the Distributed Referee Anti-Cheat Scheme (DRACS); which maximise game scalability, responsiveness, and fairness, while maintaining cheat detection/prevention equal to that in C/S. Each proposed architecture utilises one or more trusted referees to validate the game simulation - similar to the server in C/S - while allowing players to exchange updates directly - similar to peers in P2P.RACS is a hybrid C/S and P2P architecture that improves C/S by using a referee in the server. RACS allows honest players to exchange updates directly between each other, with a copy sent to the referee for validation. By allowing P2P communication RACS has better responsiveness and fairness than C/S. Further, as the referee is not required to forward updates it has better bandwidth and processing scalability. The RACS protocol could be applied to any existing C/S game. Compared to P2P protocols RACS has lower delay, and allows players with high delay to participate. Like in many P2P architectures, RACS divides time into rounds. We have proposed two efficient solutions to find the optimal round length such that the total system delay is minimised.MRACS combines the RACS and MS architectures. A referee is used at each mirror to validate player updates, while allowing players to exchange updates directly. By using multiple mirrored referees the bandwidth required by each referee, and the player-to mirror delays, are reduced; improving the scalability, responsiveness and fairness of RACS, while removing its single point of failure. Direct communication MRACS improves MS in terms of its responsiveness, fairness, and scalability. To maximise responsiveness, we have defined and solved the Client-to-Mirror Assignment (CMA) problem to assign clients to mirrors such that the total delay is minimised, and no mirror is overloaded. We have proposed two sets of efficient solutions: the optimal J-SA/L-SA and the faster heuristic J-Greedy/L-Greedy to solve CMA.DRACS uses referees distributed to player hosts to minimise the publisher / developer infrastructure, and maximise responsiveness and/or fairness. To prevent colluding players cheating DRACS requires every update to be validated by multiple unaffiliated referees, providing cheat detection / prevention equal to that in C/S. We have formally defined the Referee Selection Problem (RSP) to select a set of referees from the untrusted peers such that responsiveness and/or fairness are maximised, while ensuring the probability of the majority of referees colluding is below a pre-defined threshold. We have proposed two efficient algorithms, SRS-1 and SRS-2, to solve the problem.We have evaluated the performances of RACS, MRACS, and DRACS analytically and using simulations. We have shown analytically that RACS, MRACS and DRACS have cheat detection/prevention equivalent to that in C/S. Our analysis shows that RACS has better scalability and responsiveness than C/S; and that MRACS has better scalability and responsiveness than C/S, RACS, and MS. As there is currently no publicly available traces from MMOG we have constructed artificial and realistic inputs. We have used these inputs on all simulations in this thesis to show the benefits of our proposed architectures and algorithms

Serious games: design and development

With the growth of the video game industry, interest in video game research has increased, leading to the study of Serious Games. Serious Games are generally perceived as games that use the video games’ capabilities to emerge players, for other purposes besides entertainment. These purposes include education and training, among others. By using Serious Games for education, teachers could capture the students’ attention in the same way that video games often do, thus the learning process could be more efficient. Additionally, by exploiting the potential of these virtual worlds, it is possible to experience situations that would otherwise be very difficult to experience in the real world, mainly due to reasons of cost, safety and time. Serious Games research and development is still very scarse. However, nowadays there is a large number of available platforms and tools, which can be used to develop Serious Games and video games in general. For instance, web browsers can now provide easy access to realistic 3D virtual worlds. This grants video game developers the tools to create compelling and rich environments that can be accessed by anyone with an internet connection. Additionnaly, other development platforms can be used to achieve different goals. Desktop technologies provide greater processing power and achieve greater results in terms of visual quality, as well as in terms of creating more accurate simulations. This disseration describes the design and development of two Serious Games, one for PC, developed with XNA, and another for the web, developed with WebGL.O crescimento da indústria dos jogos de vídeo, despoletou um maior interesse no estudo deste fenómeno, o que consequentemente levou ao estudo de Jogos Sérios. Jogos Sérios são normalmente considerados jogos de vídeo que são desenvolvidos para outros fins para além do entretenimento. Estes fins incluem a educação e o treino, entre outros. Ao utilizar Jogos Sérios para a educação, os docentes poderiam conseguir captar a atenção dos alunos da mesma forma que os jogos de vídeo normalmente conseguem. Desta forma o processo de aprendizagem poderia ser mais eficiente. Adicionalmente, ao explorar o potencial destes mundos virtuais, é possível experienciar situações que de outra forma seriam difíceis de experienciar na vida real, devido ao seu custo, a razões de segurança e também ao tempo dispendido para as realizar. O estudo de Jogos Sérios é ainda bastante disperso. No entanto, hoje em dia existe já um grande número de plataformas e ferramentas disponíveis que podem ser usadas para desenvolver Jogos Sérios. Por exemplo, os web browsers podem agora fornecer acesso fácil a mundos virtuais 3D. Isto permite que os criadores de jogos de vídeo tenham acesso às ferramentas necessárias para criar ambientes ricos, que possam ser acedidos por qualquer pessoa através de uma ligacção à internet. Adicionalmente, existem outras plataformas de desenvolvimento que podem ser utilizadas para alcançar objetivos diferentes. Tecnologias desktop fornecem um maior poder de processamento e permitem alcançar melhores resultados em termos de qualidade visual, bem como em termos de criação de simulações mais precisas. Nesta dissertação descreve-se a criação e o desenvolvimento de dois Jogos Sérios, um para PC, desenvolvido em XNA e outro outro para a web, desenvolvido em WebGL

Building Robust Distributed Infrastructure Networks

Many competing designs for Distributed Hash Tables exist exploring multiple models of addressing, routing and network maintenance. Designing a general theoretical model and implementation of a Distributed Hash Table allows exploration of the possible properties of Distributed Hash Tables. We will propose a generalized model of DHT behavior, centered on utilizing Delaunay triangulation in a given metric space to maintain the networks topology. We will show that utilizing this model we can produce network topologies that approximate existing DHT methods and provide a starting point for further exploration. We will use our generalized model of DHT construction to design and implement more efficient Distributed Hash Table protocols, and discuss the qualities of potential successors to existing DHT technologies

Collaborative Game-based Learning - Automatized Adaptation Mechanics for Game-based Collaborative Learning using Game Mastering Concepts

Learning and playing represent two core aspects of the information and communication society nowadays. Both issues are subsumed in Digital Education Games, one major field of Serious Games. Serious Games combine concepts of gaming with a broad range of application fields: among others, educational sectors and training or health and sports, but also marketing, advertisement, political education, and other societally relevant areas such as climate, energy, and safety. This work focuses on collaborative learning games, which are Digital Educational Games that combine concepts from collaborative learning with game concepts and technology. Although Digital Educational Games represent a promising addition to existing learning and teaching methods, there are different challenges opposing their application. The tension between a game that is supposed to be fun and the facilitation of serious content constitutes a central challenge to game design. The often high technical complexity and especially the instructors' lack of control over the game represent further challenges. Beyond that, the distinct heterogeneity of learners who often have different play styles, states of knowledge, learning speed, and soft skills, such as teamwork or communication skills, forms a pivotal problem. Apart from that, the vital role of the instructor needs to be taken into account. Within the scope of this dissertation, the problems mentioned above are analyzed, concepts to solve them introduced, and methods developed to address them. The first major contribution contains the conceptualization of a framework for adaptation of collaborative multiplayer games as well as for the control of those games at run-time through an instructor using the Game Master principle. The core concept hereby addresses the design of a model to represent heterogeneous groups and to represent collaborative Serious Games. Based on that, a novel concept for adaptation of collaborative multiplayer games is developed, implemented, and evaluated. Automatic recognition and interpretation of game situations, as well as determination of the most well suited adaptation based on the recognized situations, is a major challenge here. Further, a concept is developed to integrate an instructor in a meaningful way into the course of the game, giving him/her the necessary resources to recognize problems and to intervene and adapt the game at run-time. Therefore, it will be taken into account that the elaborated concepts are applicable in a generic way independent of the underlying game. The second major contribution of this work is the conceptualization and design of a simulation of players and learners in a collaborative multiplayer game that behave realistically based on a player, learner, and interaction model. This is supposed to enable an evaluation of the adaptation and Game Mastering concepts using freely configurable player and learner types. The concepts introduced and developed within this thesis have been thoroughly evaluated using a twofold approach. As a test environment, a collaborative multiplayer Serious Game was designed and implemented. Within that simulation environment, the developed Game Mastering and adaptation concepts were assessed and tested with large sets of virtual learners. Additionally, the concepts were evaluated with real users. Therefore, two different evaluation studies with a total of 60 participants were conducted. The results of the conducted evaluations help to broaden the areas of application of Serious Games as well as to improve their applicability, hence raising acceptance among instructors. The models, architectures, and software solutions developed within this thesis thus build a foundation for further research of multiplayer Serious Games