Our research focuses on the assessment and resource provisioning for various types of traffic (voice, video, data and multimedia) over wired, wireless and optical networks. We aim at providing "acceptable quality" to the end-user operating in the above listed networks. We identify ourselves with the following research areas:
Optical Networks, Mobility, Quality of Service, Physical Layer, and Security

  • Optical Networks

    Benjamin Chen, Huan Liu, Fouad Tobagi

    We are investigating the design of networks having both optical and electronic switching capabilities.  Optical switching is used to support high transport capacity, whereas electronic switching is used to intelligently groom and route traffic.  A reconfigurable logical topology can be constructed of lightpaths in the optical layer.  Due to the computational complexity of the problem, existing work on designing a logical topology assumes that the physical topology is given.  We investigate the relationship between the physical topology and its supportable logical topologies and traffic patterns, in order to design cost-effective next generation optical networks.

  • Mobility in Cellular and Wireless Local Area Networks

    Cristina-Ana-Maria Hristea, Mukesh Hira, Fouad Tobagi

    We are investigating the impact of user mobility on the quality of
    multimedia applications in the Internet, including packet voice, video and
    data. We explore mobility issues that cut across many layers in the
    protocol stack, including physical, MAC, networking and transport layers.
    We investigate schemes for mobile user tracking, routing and data delivery
    that aim to optimize the user-perceived quality of multimedia applications
    and network cost.

  • Performance Assessment and Traffic Differentiation in Wireless Local Area Networks

    David Hole, Fouad Tobagi

    We are assessing the ability of wireless LANs based on the IEEE 802.11 standards to carry a wide range of traffic and in a variety of scenarios. Although this work is being carried out primarily through simulation, emphasis is placed upon the realism of the entire model -- from the channel, through the protocol stack and ultimately considering an end user's perception of performance. One goal of this work is to assess the determine the level of need for enhancements at the medium access control (MAC) layer in order to provide some form of service differentiation according to traffic requirements.

  • Link Adaptation in Wireless Local Area Networks

    Lola Awoniyi, Fouad Tobagi

    We aim to improve the performance of wireless Local Area Networks (WLANs) by dynamically adapting parameters in the Data link and the Physical layers to both the wireless channel and the traffic. These parameters include data rate (modulation and code rate), power, multiple antenna configurations, fragment size and the maximum number of retransmission. Our goal is to develop adaptation mechanisms and protocols that significantly improve the performance of the WLANs as well as have low implementation complexity.  We will be also be considering channel estimation techniques for WLANs operating in time-varying wireless channel.

  • Design of Wireless Ad Hoc Networks

    Amit Vyas, Fouad Tobagi

    We are looking at wireless ad hoc networks in the context of indoor office environments, and trying to understand how the performance varies across different applications, network scenarios and choice of protocols. It is seen that the performance at the application layer is greatly affected by the physical channel characteristics and the choice of various parameters at the physical layer, e.g. transmission power, transmission rate, and carrier sense threshold. The choice of routing protocol can also cause a significant variation in performance achieved. Based on our analyses, we intend to develop realistic protocols that could be deployed in practice and improve the performance beyond that achievable with existing protocols.

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