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Articles 1 - 26 of 26
Full-Text Articles in Physical Sciences and Mathematics
2d Barcodes As Watermarks In Image Authentication, Prashan Premaratne, Farzad Safaei
2d Barcodes As Watermarks In Image Authentication, Prashan Premaratne, Farzad Safaei
Professor Farzad Safaei
2D barcodes are increasingly used as tags in every type of goods for unique identification. Compared with the 1D barcodes, 2D barcodes not only can carry more data but also can withstand errors in subsequent scans. This property has significant parallels to watermarking logos as such watermarks will withstand multiple manipulations that are common with image transactions. We use a 2D Barcode as the watermark as this has error correction capabilities and show that this can be used to insert data imperceptibly into the host image. One Barcode is inserted into the low frequency component of the image and a …
Supporting A Seamless Map In Peer-To-Peer System For Massively Multiplayer Online Role Playing Games, Xinbo Jiang, Farzad Safaei
Supporting A Seamless Map In Peer-To-Peer System For Massively Multiplayer Online Role Playing Games, Xinbo Jiang, Farzad Safaei
Professor Farzad Safaei
Massively Multiplayer Online Role Playing Games feature huge maps that can be partitioned into smaller components called zones to achieve scalability. In peer-to-peer (P2P) systems, those zones can be assigned to peers who are willing to take up the role of zone servers. A seamless map requires inter-zone communications to allow interactions between players across zone boundaries. In assigning zones to peers, it is critical to seek approaches to reduce the inter-zone communication cost in P2P system. In this paper, we formulate the zone assignment problem for P2P system and demonstrate that the problem is NP-hard. We hence propose a …
A Survey On Control Separation Techniques In Multi-Radio Multi-Channel Mac Protocols, Jerry Chun-Ping Wang, Mehran Abolhasan, Farzad Safaei, D. Franklin
A Survey On Control Separation Techniques In Multi-Radio Multi-Channel Mac Protocols, Jerry Chun-Ping Wang, Mehran Abolhasan, Farzad Safaei, D. Franklin
Professor Farzad Safaei
The rapid diminishing in the cost of commodity wireless hardware in recent years has prompted the use of multiple radios to improve the capacity of wireless networks. However, the research has shown that the improvement obtained from using multiple radios does not solely depend on the number of radios, but primarily on how these radios can be integrated in a constructive manner. A common way of integration multiple radios is to use a dedicated radio for control. To date, a number of multi-radio MAC protocol are employing a dedicated radio to control and coordinate the other radios, though the approaches …
Enhancing The Multicast Performance Of Structured P2p Overlay In Supporting Massively Multiplayer Online Games, Xinbo Jiang, Farzad Safaei, P. Boustead
Enhancing The Multicast Performance Of Structured P2p Overlay In Supporting Massively Multiplayer Online Games, Xinbo Jiang, Farzad Safaei, P. Boustead
Professor Farzad Safaei
Scribe is a scalable application level multicast infrastructure. We have developed two techniques to improve the performance of Scribe in terms of latency and bandwidth distribution. The first technique identifies that the final hop of Scribe traffic path is largely selected without any proximity consideration and incurs the longest distance traveled. To overcome this, we introduce Proximity Neighbor Selection (PNS) into the final hop for latency improvement. The second technique builds a hierarchical two-level overlay. While PNS can be applied at both levels for latency performance, the bandwidth stress required by applications can now be distributed among the nodes in …
Distributed Server Delivery Of Immersive Voip Service: Balancing Between Voice Latency And Access Upload Cost, Ying Peng Que, Farzad Safaei, P. Boustead
Distributed Server Delivery Of Immersive Voip Service: Balancing Between Voice Latency And Access Upload Cost, Ying Peng Que, Farzad Safaei, P. Boustead
Professor Farzad Safaei
As a future communication tool to the Distributed Virtual Environment, the Immersive VoIP service delivers to each user a real-time mix of nearby user voices which are all rendered according to their respective virtual world positions. In this work, we conjecture that the voice latency constraints between Immersive VolP users would vary according to their virtual world distance of separation. As verified in our subjective listening tests, this conjecture is more realistic than fixed latency constraint, in terms of user perceptual experience and network feasibility. Empowered by the Bandwidth Reduced server assignment algorithm, the proposed two-hop distributed server architecture achieves …
On Separating Route Control And Data Flows In Multi-Radio Multi-Hop Ad Hoc Network, Jerry Chun-Ping Wang, Mehran Abolhasan, D. Franklin, Farzad Safaei, Justin Lipman
On Separating Route Control And Data Flows In Multi-Radio Multi-Hop Ad Hoc Network, Jerry Chun-Ping Wang, Mehran Abolhasan, D. Franklin, Farzad Safaei, Justin Lipman
Professor Farzad Safaei
Ad hoc networks typically require a significant amount of routing and control information to be distributed in a timely and reliable manner throughout the network, particularly in dynamic environments. As traffic levels increase and the network becomes more heavily congested, there is an increased probability that these critical packets are lost, resulting in obsolete control information being used to make important decisions. This would further compound the problem of network congestion and lead to a very rapid loss of connectivity and throughput. Given this, we argue the solutions to these problems should not rely on putting extra bandwidth on a …
Latency And Scalability: A Survey Of Issues And Techniques For Supporting Networked Games, Xinbo Jiang, Farzad Safaei, P. Boustead
Latency And Scalability: A Survey Of Issues And Techniques For Supporting Networked Games, Xinbo Jiang, Farzad Safaei, P. Boustead
Professor Farzad Safaei
The popularity of on-line games that emphasize real-time interactivity is on the rise. A survey of issues and techniques for supporting on-line games is provided in this paper. Latency and scalability are two primary aspects on which this survey is based. Network latency heavily influences the design of on-line games with regards to the nature of interactivities involved, as well as, real-time flows such as voice and video if enhanced user immersive experiences are required. As a consequence, a trade-off between consistency and responsiveness, the two latency-related artifacts, is usually needed. This can be demonstrated through a number of latency …
A Hybrid Optical Network Architecture Consisting Of Optical Cross Connects And Optical Burst Switches, Chuntung Chou, Farzad Safaei, P. Boustead, I. Ouveysi
A Hybrid Optical Network Architecture Consisting Of Optical Cross Connects And Optical Burst Switches, Chuntung Chou, Farzad Safaei, P. Boustead, I. Ouveysi
Professor Farzad Safaei
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 …
End-To-End Path Stability Of Reactive Routing Protocols In Ieee 802.11 Ad Hoc Networks, Daniel R. Franklin, Jerry Chun-Ping Wang, Mehran Abolhasan, Farzad Safaei
End-To-End Path Stability Of Reactive Routing Protocols In Ieee 802.11 Ad Hoc Networks, Daniel R. Franklin, Jerry Chun-Ping Wang, Mehran Abolhasan, Farzad Safaei
Professor Farzad Safaei
Over the years, a considerable research effort has been applied to the design of ad hoc network routing protocols. However, there is still a lack of understanding of the subtle interactions between routing protocols and lower layers in the protocol stack. In this paper, the instability which may arise when reactive routing protocols interact with the IEEE 802.11 MAC protocol is investigated. In particular, several erratic behaviours of the Ad hod On-demand Distance Vector (AODV) routing protocol in a congested IEEE 802.11 ad hoc network are demonstrated. A cross-layer solution is proposed based on an Adaptive Bulk Trigger policy and …
A Recursive Overlay Multicast Algorithm For Distribution Of Audio Streams In Networked Games, M. Dowlatshahi, Farzad Safaei
A Recursive Overlay Multicast Algorithm For Distribution Of Audio Streams In Networked Games, M. Dowlatshahi, Farzad Safaei
Professor Farzad Safaei
This paper aims to provide a fast multicast algorithm among a set of distributed proxies to enable the creation of realistic audio for networked games. We assume that each proxy is responsible for a group of clients. The proxy receives the audio packets from its clients and multicasts this audio to every other proxy that requires this audio for any of its attached clients. In crowded virtual environments, the number of multicast trees could be quite large and these undergoes continuous change as the avatars move in and out of each others hearing range. To reduce the effect of overhead …
Dice: Internet Delivery Of Immersive Voice Communication For Crowded Virtual Spaces, P. Boustead, Farzad Safaei, M. Dowlatshahi
Dice: Internet Delivery Of Immersive Voice Communication For Crowded Virtual Spaces, P. Boustead, Farzad Safaei, M. Dowlatshahi
Professor Farzad Safaei
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 …
Non-Scalar Economy: An Incentive-Based Approach For Managing Pollution And Attaining Economic Sustainability, Farzad Safaei
Non-Scalar Economy: An Incentive-Based Approach For Managing Pollution And Attaining Economic Sustainability, Farzad Safaei
Professor Farzad Safaei
In the current economy, the cost of damage to the environment is often external, which is likely to lead to over-exploitation and inadequate provisioning. There are a variety of incentive-based schemes, such as effluent taxes or tradable permits, which attempt to confront the polluting agents with a ‘price’ equal to the marginal external cost of their activity. However, competitive incentives alone are not adequate for effective management of the shared resources. Thus, the current solutions exhibit several drawbacks including susceptibility to international free-riding, sensitivity to accurate estimation of cost of pollution or environmental targets, and inability to take the cumulative …
Solution Of A Certain Class Of Network Flow Problems With Cascaded Demand Aggregation And Capacity Allocation, Farzad Safaei, I. Ouveysi
Solution Of A Certain Class Of Network Flow Problems With Cascaded Demand Aggregation And Capacity Allocation, Farzad Safaei, I. Ouveysi
Professor Farzad Safaei
This article develops analytical models for a class of networking problems that includes two cascaded stages of demand aggregation and capacity allocation. The solutions to these problems are required in real time as the demand fluctuates rapidly. The capacity allocation problem makes a large-scale integer programming problem too complex for practical applications. Using the Lagrangian relaxation technique and a suitably developed heuristic for multiplier adjustment, the computational complexity is reduced to such a degree that a real-time implementation of the algorithm is feasible. This article also develops efficient heuristics to aggregate demand. The proposed algorithm produces a near-optimal solution in …
Minimising The Computational Cost Of Providing A Mobile Immersive Communication Environment (Mice), Ying Peng Que, Paul Boustead, Farzad Safaei
Minimising The Computational Cost Of Providing A Mobile Immersive Communication Environment (Mice), Ying Peng Que, Paul Boustead, Farzad Safaei
Professor Farzad Safaei
This paper investigates the minimisation of the computational cost of providing Immersive Voice Communication (IVC) for mobile clients attached to a Distributed Virtual Environment (DVE). When experiencing IVC, each listening avatar in the DVE, receives a mix of the surrounding avatars’ voices, all rendered according to their respective positions in the virtual world. We propose to deliver our mobile IVC service using a type of server-based network architecture to perform voice spatialisation function and mixing for each mobile client. This model will minimise both the access bandwidth and processing power requirements of the mobile devices. We propose a model for …
Multipoint Interactive Communication For Peer To Peer Environments, Mehran Dowlatshahi, Farzad Safaei
Multipoint Interactive Communication For Peer To Peer Environments, Mehran Dowlatshahi, Farzad Safaei
Professor Farzad Safaei
In this paper a scheme for peer-to-peer (p2p) multiparty voice communication is proposed. The paper considers realistic constraints on the upstream and downstream bandwidth of peers and their processing capacity. We propose a novel mechanism for distributed mixing of the audio streams that can improve the scalability of this service while meeting the capacity constraints. The paper also proposes an algorithm to form a multipoint-to-multipoint spanning tree (MMST) among the peers within a communication zone. The simulation results show that the performance of algorithm in terms of delay stretch and its impact on bandwidth reduction in comparison to multiple source …
A Distributed Server Architecture For Providing Immersive Audio Communication To Massively Multiplayer Online Games, C. D. Nguyen, Farzad Safaei, P. Boustead
A Distributed Server Architecture For Providing Immersive Audio Communication To Massively Multiplayer Online Games, C. D. Nguyen, Farzad Safaei, P. Boustead
Professor Farzad Safaei
This paper investigates the assignment of audio mixing operations to a geographically distributed set of servers to provide an immersive audio communication environment for massively multiplayer online games. The immersive audio communication service enables each avatar to hear a realistic audio mix of the conversations in its audible range. There are three primary delivery architectures for this service, namely, peer-to-peer, central server and distributed servers. We focus on the 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 …
An Architecture For Carrier Grade Programmable Networks, T. V. Nguyen, P. Boustead, Farzad Safaei
An Architecture For Carrier Grade Programmable Networks, T. V. Nguyen, P. Boustead, Farzad Safaei
Professor Farzad Safaei
Active and programmable networks allow innovative new services to be deployed rapidly. However, in a carrier grade network, it is imperative to maintain a scalable fast path mechanism so that the delay and throughput requirements are met. This is particularly important since, in many cases, network-level processing is only needed for a subset of packets and the remainder of traffic must be forwarded on the fast path. It is a challenge to design a cost effective node architecture that can satisfy this requirement. Current models are often 'revolutionary' and may not scale to the required performance levels of a carrier …
Performance Evaluation Of A Proxy System For Providing Immersive Audio Communication To Massively Multi-Player Games, C. D. Nguyen, Farzad Safaei, P. Boustead
Performance Evaluation Of A Proxy System For Providing Immersive Audio Communication To Massively Multi-Player Games, C. D. Nguyen, Farzad Safaei, P. Boustead
Professor Farzad Safaei
In this paper, a distributed proxy architecture is introduced for the provisioning of an immersive audio communication service to massively multi-player online games. The immersive audio communication service enables each avatar to hear a realistic audio mix of conversations in its hearing range. In our earlier work, peer-to-peer and central server architectures have been proposed for this service. In this paper, a distributed proxy architecture with either using network multicast or unicast between proxies is introduced to address the limitations of the previous architectures. The main focus of this paper is to evaluate the bandwidth cost saving of network multicast …
Managing Latency And Fairness In Networked Games, J. Brun, Farzad Safaei, P. Boustead
Managing Latency And Fairness In Networked Games, J. Brun, Farzad Safaei, P. Boustead
Professor Farzad Safaei
Networked games can be seen as forerunners of all kinds of participatory entertainment applications delivered through the Internet. Physically dispersed players are immersed in a common virtual environment where they interact in real time. When a user performs an action, other users must be made aware of that action. Otherwise, there is a discrepancy in the perceptions of participants about the overall state of the virtual world. This discrepancy could lead to undesirable and sometimes paradoxical outcomes. In particular, first-person shooter, and to a lesser extent role-playing games impose stringent constraints on responsiveness and consistency.
Resilience-Differentiation In Programmable Virtual Networks, F. Rosenbaum, S. Jha, P. Boustead, Farzad Safaei
Resilience-Differentiation In Programmable Virtual Networks, F. Rosenbaum, S. Jha, P. Boustead, Farzad Safaei
Professor Farzad Safaei
Service and application requirements on network resilience have increased over the past few years. New on-line services such as e-commerce and connection-oriented interactive real-time services require higher network resilience than the more traditional off-line services. Programmable virtual networks promise fast and easy provisioning of new services but no consideration to meet the diverse resilience requirements has been made. This paper discusses issues related to resilience-differentiation in programmable virtual networks. A set of general guidelines is presented that apply to resilience-differentiation in programmable virtual network architectures. A case study is used to illustrate how the proposed guidelines can be met by …
Latency-Driven Distribution: Infrastructure Needs Of Participatory Entertainment Applications, Farzad Safaei, P. Boustead, C. D. Nguyen, J. Brun, M. Dowlatshahi
Latency-Driven Distribution: Infrastructure Needs Of Participatory Entertainment Applications, Farzad Safaei, P. Boustead, C. D. Nguyen, J. Brun, M. Dowlatshahi
Professor Farzad Safaei
This article evaluates network and server infrastructure requirements to support real-time flows associated with networked entertainment applications. These include the state information flow to update the status of the virtual environment and immersive communication flows such as voice, video, gesture, and haptics communication. The article demonstrates that scaling these applications to large geographical spreads of participants requires distribution of computation to meet the latency constraints of the applications. This latency-driven distribution of computation is essential even when there are no limitations on the availability of computational resources in one location. The article provides detailed results on distributed server architectures for …
On The Provision Of Immersive Audio Communication To Massively Multi-Player Online Games, C. D. Nguyen, Farzad Safaei, D. Platt
On The Provision Of Immersive Audio Communication To Massively Multi-Player Online Games, C. D. Nguyen, Farzad Safaei, D. Platt
Professor Farzad Safaei
This paper discusses issues in providing immersive audio communication to massively multi-player online games (MMOG). We focus on network and server architectures for creating immersive audio scenes for game clients. We examine advantages and limitations of several architectures, including central server, distributed servers, and peer-to-peer architectures. We focus on a dynamic centralized server architecture which is suitable for the current MMOG in terms of sealability at end users and resource efficiency. We propose algorithms to optimize the performance of a centralized server. Finally, a simulation study is carried out to evaluate the performance of our proposed centralized server architecture and …
Characterising The Behaviour Of Ieee 802.11 Broadcast Transmissions In Ad Hoc Wireless Lans, Mehran Abolhasan, Farzad Safaei, Jerry Chun-Ping Wang, Daniel R. Franklin
Characterising The Behaviour Of Ieee 802.11 Broadcast Transmissions In Ad Hoc Wireless Lans, Mehran Abolhasan, Farzad Safaei, Jerry Chun-Ping Wang, Daniel R. Franklin
Professor Farzad Safaei
This paper evaluates the performance of the IEEE 802.11 broadcast traffic under both saturation and nonsaturation conditions. The evaluation highlights some important characteristics of IEEE 802.11 broadcast traffic as compared to corresponding unicast traffic. Moreover, it underlines the inaccuracy of the broadcast saturation model proposed by Ma and Chen due to the absence of backoff counter freeze process when channel is busy. Computer simulations are used to validate the accuracy of the new model and demonstrate the importance of capturing the freezing of backoff counter in the analytical study of IEEE 802.11 broadcast.
Olsr-R^3: Optimised Link State Routing With Reactive Route Recovery, Jerry Chun-Ping Wang, Farzad Safaei, Mehran Abolhasan, Daniel R. Franklin
Olsr-R^3: Optimised Link State Routing With Reactive Route Recovery, Jerry Chun-Ping Wang, Farzad Safaei, Mehran Abolhasan, Daniel R. Franklin
Professor Farzad Safaei
The Optimised Link State Routing (OLSR) is a proactive routing protocol which relies on periodical broadcast of routing packets. However, due to the one-to-many relationship of broadcast traffic, the delivery of these packets can not be guaranteed by underlying MAC protocol, particularly in a congested condition. In this paper, the possible routing pathologies and failures of OLSR in a congested network are explored. In addition, a hybrid routing protocol which integrates OLSR with Reactive Route Recovery (OLSR-R3) is proposed to rectify the erratic routing behaviour described in this paper. Simulation studies are presented which show that the proposed solution is …
Investigation And Modeling Of Traffic Issues In Immersive Audio Environments, J. Mcmahon, M. Rumsewicz, P. Boustead, Farzad Safaei
Investigation And Modeling Of Traffic Issues In Immersive Audio Environments, J. Mcmahon, M. Rumsewicz, P. Boustead, Farzad Safaei
Professor Farzad Safaei
A growing area of technical importance is that of distributed virtual environments for work and play. For the audio component of such environments to be useful, great emphasis must be placed on the delivery of high quality audio scenes in which participants may change their relative positions. In this paper we describe and analyze an algorithm focused on maintaining relative synchronization between multiple users of such an environment and examine the subjective quality of service achieved.
Macro-Economic Equilibrium And Price Signal Accuracy In Non-Scalar Economy, Farzad Safaei
Macro-Economic Equilibrium And Price Signal Accuracy In Non-Scalar Economy, Farzad Safaei
Professor Farzad Safaei
The management of global commons is of vital importance for modern society. The current solutions attempt to internalize the cost of appropriation of commons by adding this to the cost of private resources. In this paper we will show that this approach has some fundamental weaknesses. To overcome these shortcomings, we have proposed to segregate the management of private and shared resources by using non-scalar numbers for the underlying economic signals of money and price. We prove that the resulting non-scalar economy always reaches a macro-economic equilibrium point where the level of appropriation of commons by the society remains steady. …