Fouad A. Tobagi

Stanford University

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S.-H. Gary Chan

National Taipei University of Technology

M Karam

Lusíada University of Lisbon

I. Dalgic

Stanford University

Athina Markopoulou

International Hellenic University

Jon M. Peha

Carnegie Mellon University

Leonard Kleinrock

University of California, Los Angeles

K. Medepalli

Stanford University

Ciro A. Noronha

Imperial College London

Yitzhak Birk

Technion – Israel Institute of Technology

F.M. Chiussi

Cisco Systems (United States)

Cooperative Institutions

Stanford University

University of Illinois Urbana-Champaign

Nokia (United States)

University of Illinois System

United States Naval Research Laboratory

AT&T (United States)

University of California, Los Angeles

Massachusetts Institute of Technology

University of Maryland, College Park

The University of Texas at Austin

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"Supernodes" in Networks Employing Spread Spectrum with Code Division Multiple Access.

Computer Networks (1988)

Yitzhak Birk Fouad A. Tobagi

Code (set theory)

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Citations (0)

IP Routing and Mobility

Lecture notes in computer science (2001)

Cristina Hristea Fouad A. Tobagi

Triangular routing

Mobility model

10.1007/3-540-45400-4_19

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Citations (2)

Optical Network Design to Minimize Switching and Transceiver Equipment Costs

Benjamin Chen Fouad A. Tobagi

We consider a network consisting of N nodes and a certain number of links that could be used to interconnect these nodes. The problem we address is to determine the smallest subset of switching nodes (in which to provide optical or electronic switching capability) necessary and sufficient to provide full end- to-end connectivity among all nodes. It is shown that this selection leads to the minimum number of transceivers needed to achieve full connectivity. We then address the same problem with the additional requirement of survivability, whereby the failure of any one link does not lead to any disconnection in the network. To solve the above stated problems, we present heuristic and optimal algorithms, and we study how the number of switches varies with the number of potential links.

Transceiver

Survivability

Disconnection

10.1109/broadnets.2006.4374389

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Citations (3)

A feedback control scheme for low latency constant quality MPEG-2 video encoding

Andrea Basso I. Dalgic Fouad A. Tobagi C. van den Branden Lambrecht

Constant (computer programming)

MPEG-2

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Network Topology Design to Optimize Link and Switching Costs

IEEE International Conference on Communications (2007)

B. K. Chen Fouad A. Tobagi

We consider the problem of designing a network which minimizes the total cost of the switching facilities and the fiber links, by choosing the subset of nodes at which to install switching functionality and the subset of the available fiber links to employ for interconnecting nodes. This objective addresses jointly two of the most significant costs in the design of a communications network - the number of switching sites and the total linear distance of the utilized links - and results in substantial cost benefits. Since relative costs vary depending on specific circumstances, we characterize the tradeoff between the number of switching sites and the total link length. Our study is performed for a network supporting full connectivity between all nodes, rather than for a specific traffic matrix, and thus reveals fundamental properties inherent to the given topology. We address both the unprotected and the protected cases, and we present heuristic algorithms to solve the problem.

Link (geometry)

10.1109/icc.2007.354

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Citations (9)

Random access techniques for data transmission over packet-switched radio channels

Leonard Kleinrock Fouad A. Tobagi

On the other hand, digital (pulse) systems using radio propagation are not new-e.g., telegraphy, radar, etc.Here we restrict our comments to addressed packets.The most well known example of a packet switched wire network is the ARPANET."* See References 14 and 15 for proof and for the definition of m(0, T m ), B and /. * The bandwidth is assumed to be modulated a 1 bit/Hz-sec.t This corresponds to a maximum distance of about 20 miles.The ratio of propagation delay to transmission time of a packet, denoted by a, is, in all cases less than (but very close to) or equal to 0.01.

Random access

Packet radio

Packet Switching

10.1145/1499949.1499984

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Citations (101)

Routing of Streams in WDM Reconfigurable Networks

Ciro A. Noronha Fouad A. Tobagi

Due to its low attenuation, fiber has become that medium of choice for point-to-point links. Using Wavelength-Division Multiplexing (WDM), many channels can be created in the same fiber. A network node equipped with a tunable optical transmitter can select any of these channels for sending data. An optical interconnection combines the signal from the various receivers in the network, and makes it available to the optical receivers, which may also be tunable. By properly tuning transmitters and/or receivers, point-to-point links can be dynamically created and destroyed. Therefore, in a WDM network, the routing algorithm has an additional degree of freedom compared to traditional networks: it can modify the network topology to create the routes. In this report, we consider the problem of routing audio/video streams in WDM networks. We present a general linear integer programming formulation for the problem. However, since this is a complex solution, we propose simpler heuristic algorithms, both for the unicast case and for the multicast case. The performance of these heuristics is evaluated in a number of scenarios, with a realistic traffic model, and from the evaluation we derive guidelines for usage of the heuristic algorithms.

Heuristics

Unicast

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Routing of multicast audio/video streams in reconfigurable WDM optical networks

Journal of Network and Systems Management (1996)

Ciro A. Noronha Fouad A. Tobagi

10.1007/bf02139132

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Citations (1)

On achieving profit in providing near video-on-demand services

S.-H. Gary Chan Fouad A. Tobagi

In near video-on-demand, requests for the same movie arriving within a period of time are grouped together (i.e., batched) and served with a single multicast stream; thereby reducing the bandwidth requirement compared with the unbatched case. We consider here that the use of a multicast channel comes with a cost. Since delayed users may cancel their requests while being batched, this uncollected revenue has to be appropriately balanced with the channel usage cost in order to achieve maximum profit. We address profit issues for a number of batching schemes. In the window-based schemes, users are batched for a fixed period of time before they are served; in the batch-size based scheme, users are served once a certain number of them are collected. We study the system profit in terms of user reneging behavior, movie popularity, and multicast channel cost. By combining the advantages of the window-based and the batch-size based schemes, we introduce a scheme which adapts to the fluctuating request rate to achieve high profit.

Video on demand

Popularity

10.1109/icc.1999.765422

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Citations (12)

System centric and user centric queueing models for IEEE 802.11 based wireless LANs

K. Medepalli Fouad A. Tobagi

We consider the following two views of an IEEE 802.11 based Wireless LAN: (i) as seen by the WLAN medium and (ii) as seen by a user. In the system centric view, we model the WLAN medium as a server that allocates its resources to users in a round Robin manner. This resource sharing model not only provides a simple model for the system, it also enables us to derive the channel service rate and the total delay incurred in transmitting a packet. For Poisson arrivals, the resource sharing model takes the form of an M/G/1/PS system with the mean delay being the same as that in an equivalent M/M/1 system. We then take a user centric view and model each user's queue as a separate G/G/1 queue. We derive the probability distributions for the different delay sources, i.e., random back-off time, random number of collisions and random number of successful transmissions from other users. This user centric model can provide insights into understanding access and queuing delays in 802.11 DCF. Finally, we discuss the utility of these models for functions such as capacity analysis, admission control and QoS enforcement.

Shared resource

Random access

10.1109/icbn.2005.1589666

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Citations (43)