Behnoosh Hariri

Overlay Routing Architectures for Massively Multiuser Virtual Environments

Supervisor(s) and Committee member(s): Mohammad Hossein Alavi (supervisor), Mohammad Reza Pakravan (internal co-supervisor), Shervin Shirmohammadi (external co-supervisor)


Massively Multiuser Virtual Environments (MMVE) are network applications that simulate the experience of real-time interaction among multiple users distributed all over the internet. In order to share the common sense of time and place, multiple entities interacting in the shared virtual environment must be aware of the modifications or interactions within the shared environment. This is achieved through the distribution of update messages. As the number of users and entities increases, there is a considerable increase in the amount of update messages exchanged among the users and entities. Supporting the large of update messages, especially in massive environments, is one of the most important challenges in the design of MMVEs. The use of a distributed architecture allowing users to handle the traffic among each other in a peer to peer (P2P) fashion is one solution to this problem. However, such solution must in turn deal with a variety of challenges related to the non-centralized nature of the protocol.

This dissertation proposes a number of distributed architectures for MMVEs in an attempt to provide an efficient infrastructure for update message distribution. Simulation has also been used to demonstrate the functionality and performance of the proposed approaches. Contributions include:

  • Analytical modeling of the update exchange problem in MMVEs
  • Proposing new architectures for update message exchange in MMVEs dealing with the following two challenges:
    • Distributed architecture
    • Latency aware message delivery
  • Designing the following architectures for distributed MMVE application where no centralized control/data switching point is required:
    • DHT architecture where exchange of delay-sensitive-data is supported.
    • Hilbert Curve architecture based on mapping and routing over 3D Hilbert Curve.
    • KD Tree architecture based on mapping over Z curve and routing based on KD tree.
    • Geometric Routing architecture inspired by the concept of geometric routing in wireless networks, and adapting it to the wired networks and MMVE specific requirements.
  • Designing resilient algorithms in the presence of user churn and mobility
  • Application of the concept of fast search in multi-dimensional databases to latency-aware routing in distributed networks.

Advanced Communications Research Group (ACRI), Sharif University of Technology


ACRI was founded in 2004 as the only national Center of Excellence in Communications Systems in Iran. Situated at Sharif University of Technology, it enjoys access to the top 100 students, ranked based on the annual national entrance exam, admitted to the University's Electrical Engineering program every year (among which the top 30 students usually choose to come to the Communications program). The center conducts research in:

  1. Optical Multi-Access Systems
  2. Mobile Communications
  3. Signal Processing and Multimedia
  4. Traffic Modeling and Communication Networks
  5. Game Theory
  6. Communications Systems
  7. Microwave, Antennas, and Propagation
  8. Information Theory and Secure Communications

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