Sanjoy Paul

Video multicast over the Internet

Multicast distribution of video is an important component of many existing and future networked services. The Internet lacks support for quality of service (QoS) assurance, which makes the transmission of real-time traffic challenging. In addition, the heterogeneity of the Internets transmission resources and end-systems makes it extremely difficult, if not impossible, to agree on acceptable traffic characteristics among multiple receivers of the same video stream. We survey techniques that have been proposed for transmitting video in this environment. These generally involve adaptation of video traffic carried over the network to match receiver requirements and network conditions. In addition to their applicability to the near-term capabilities of the Internet, they also are of relevance to a future, QoS-aware Internet environment. We first consider source-based techniques in which the source adjusts the video stream traffic to match some consensus among the receivers about its desired characteristics. These techniques can result in an unfair treatment for receivers, especially those whose capability is significantly above or below the group consensus. We then consider techniques that aim to improve the fairness among the receivers by sending the video in multiple (layered or replicated) streams. We also discuss several error control mechanisms, using timely retransmission of missing data to further improve the quality of the received video. Finally, we discuss some of the issues in the development of Internet video multicast protocols.

Layered video multicast with retransmissions (LVMR): evaluation of hierarchical rate control

Layered video multicast with retransmissions (LVMR) is a system for distributing video using layered coding over the Internet. The two key contributions of the system are: (1) improving the quality of reception within each layer by retransmitting lost packets given an upper bound on recovery time and applying an adaptive playback point scheme to help achieve more successful retransmission, and (2) adapting to network congestion and heterogeneity using hierarchical rate control mechanism. This paper concentrates on the rate control aspects of LVMR. In contrast to the existing sender-based and receiver-based rate control in which the entire information about network congestion is either available at the sender (in sender-based approach) or replicated at the receivers (in receiver-based approach), the hierarchical rate control mechanism distributes the information between the sender, receivers, and some agents in the network in such a way that each entity maintains only the information relevant to itself. In addition to that, the hierarchical approach enables intelligent decisions to be made in terms of conducting concurrent experiments and choosing one of several possible experiments at any instant of time based on minimal state information at the agents in the network. Protocol details are presented in the paper together with experimental and simulation results to back our claims.

Layered video multicast with retransmission (LVMR): evaluation of error recovery schemes

This paper proposes a novel scheme for distributing MPEG-coded video over a best-effort heterogeneous network, such as the Internet. The key contributions of the proposed scheme are: error recovery using smart retransmissions and adaptive playback point; and dynamic adjustment of video reception rate at the receivers using a hierarchical control mechanism. This paper focuses on the first feature. The protocols are developed on the Internet and the performance of the system has been measured on the Mbone. Some results from the measurement are presented and evaluated in this paper.

Multi-Session Rate Control for Layered Video Multicast

In a video multicast session, the receivers may possess different capabilities or be connected to the network through a variety of different access speeds. Multicasting video traffic at any one rate to all of the receivers can be unfair as some receivers may experience high losses while others find that their full reception capacity is not fully utilized. Layered video multicast protocols have been developed to address this intra-session fairness problem. In such protocols (e.g., RLM and LVMR), video is multicast in multiple layers over separate multicast groups. Receivers join as many layers as they can handle. While protocols such as RLM and LVMR have been shown to successfully address the intra-session fairness issue in video multicast, they do not address the issue of inter-session fairness, i.e., fair sharing between multiple video sessions and TCP sessions. In this paper, we demonstrate and develop insight into the inter-session fairness problem through a set of simulation experiments. We then propose a novel idea to improve inter- session fairness for layered video multicast protocol: layer-based congestion sensitivity mechanism, and finally evaluate it with some other end-to-end schemes designed to promote inter-session fairness when used to augment layered video multicast protocols.

Anonymous credit cards and their collusion analysis

Communications networks are traditionally used to bring information together. They can also be used to keep information apart in order to protect personal privacy. A cryptographic protocol specifies a process by which some information is transferred among some users and hidden from others. We show how to implement anonymous credit cards using simple cryptographic protocols. We pose, and solve, a collusion problem which determines whether it is possible for a subset of users to discover information that is designed to be hidden from them during or after execution of the anonymous credit card protocol.

Providing end-to-end QoS for multimedia applications in 3G wireless networks

As the usage of wireless packet data services increases, wireless carriers today are faced with the challenge of offering multimedia applications with QoS requirements within current 3G data networks. End-to-end QoS requires support at the application, network, link and medium access control (MAC) layers. We discuss existing CDMA2000 network architecture and show its shortcomings that prevent supporting multiple classes of traffic at the Radio Access Network (RAN). We then propose changes in RAN within the standards framework that enable support for multiple traffic classes. In addition, we discuss how Session Initiation Protocol (SIP) can be augmented with QoS signaling for supporting end-to-end QoS. We also review state of the art scheduling algorithms at the base station and provide possible extensions to these algorithms to support different classes of traffic as well as different classes of users.

A case for tree-based hierarchy as a unified framework for reliable multicasting on the Internet

Reliable multicasting encompasses a spectrum of applications with varying requirements. Also there seems to be a consensus among the researchers that a single protocol cannot serve the entire application space. Therefore, there is a need for a common framework which can support protocols specifically suited for various applications. This paper begins with a categorization of reliable multicasting applications followed by the description of key problems in each category. In addition, some partial solutions are provided to these problems using a tree-based hierarchical framework. It is argued that a tree-based hierarchy can potentially provide a scalable framework for reliable multicasting in general.