Shahab Baqai

Quality-based evaluation of multimedia synchronization protocols for distributed multimedia information systems

Distributed, networked multimedia information systems will be a critical component of technology-based information infrastructures in the future. We present an infrastructure for supporting multimedia applications. We discuss various characteristics of multimedia data and the effect of the network on the required quality of presentation for multimedia data. We present a suite of synchronization protocols to support the quality of presentation. The crux of these protocols is the scheduling of multimedia information for synchronized delivery, over broadband networks with limited resources, and is identified as an NP-hard problem. We introduce two parameters which can be used to measure the performance of end-to-end synchronization protocols in a network supporting distributed multimedia applications. We propose and implement several heuristic scheduling algorithms, and compare their performance. We deduce the appropriateness of these algorithms in different types of distributed multimedia environments.

QoS aware path selection in content centric networks

With the availability of higher network bandwidths, greater computing power, and a shift to more content centric use of the internet, researchers are revisiting the Internet architecture. One such effort is the Content Centric Networking (CCN) project where content driven data, rather than nodes, is primarily used for enabling communications. CCN include state maintenance at the intermediate network nodes and allow multiple paths to the content; two aspects absent in the current Internet architecture. In this paper, we focus on the problem of path selection in CCN. Our contribution is threefold - we propose: (i) a technique for downloading content from multiple sources simultaneously, maximizing aggregate bandwidth, (ii) a method for determining the highest bandwidth path to a single source for high bandwidth applications, and (iii) an approach for minimizing per packet delay for real time traffic. Compared to our approach, random forwarding gives only 63% of attainable bandwidth and twice the average per packet delay.

Network resource management for enterprise wide multimedia services

The support of broadband multimedia applications over an enterprise network poses a broad range of networking challenges for efficient resource management, intelligent switching, and access control for distributed information. We propose two server-based scheduling algorithms, with low computational complexity, to guarantee multimedia information synchronization at the destination, with minimum presentation delays and buffer requirements. We outline a communication framework, highlighting the issues and challenges faced by todays enterprise networks to support multimedia services. We describe the proposed connection establishment and resource allocation schemes in resource-constrained enterprise networks. The objective is to manage the limited resources of the network for maximum utilization. Towards this end we present a dynamic capacity allocation scheme to support connections for multiple users. Specifically, we show that the channel capacity allocation problem can be formulated as a quadratic programming problem. This allocation scheme is implemented at each intermediate switch to dynamically determine the capacity allocation. The effects of interswitch rate mismatch and network delay offset scheduling have also been incorporated in the management framework. In addition, we introduce the concept of route selection based on the requested network quality of service.

Wireless network resource management for Web-based multimedia document services

Advances in wireless technology and availability of portable devices with networking capabilities have enabled ubiquitous Web accessibility. This has created the need to provide advance Internet services to mobile users without causing service failures due to connection migration or handoffs. However, scarcity of wireless resources restricts the provision of multimedia services in wireless networks. We address the issue of managing wireless resources to support Web-based multimedia document services including MPEG-4-based applications, in wireless networks with a high degree of user mobility. In particular, we formulate the resource management problem in wireless networks as an optimization problem with an objective function comprising different quality of presentation parameters.

CAIP: a restoration routing architecture for DiffServ aware MPLS traffic engineering

The authors proposed an architecture for MPLS restoration routing of DiffServ traffic. This architecture, namely per class aggregate information with preemption (CAIP), facilitates provisioning of two key QoS features for multimedia traffic: prioritized guaranteed bandwidth and fast restoration in the event of an element failure. The CAIP architecture is scalable and requires propagating only per-class aggregate link usage information; such information can be readily piggybacked on link state routing packets using traffic engineering extensions to link state routing protocols (Katz et. al). CAIP results in improved bandwidth sharing compared to simple aggregate information scenario (SAIS), resulting in fewer LSP rejected requests and a greater amount of active bandwidth placed on the network. On average, CAIP rejects 881 LSP requests compared to 1010 rejected LSP requests in SAIS for a typical ISP network. Similarly, CAIP is able to place 220 units of bandwidth compared to 180 units of bandwidth placed in SAIS, thus showing an average improvement of about 22%. CAIP allows precise computation of preemptable bandwidth for an arbitrary set of prioritization requirements put forth by the service providers. A case study of service provider requirements and computation of preemptable bandwidth for those requirements were presented. CAIP can be integrated with those restoration routing schemes that make use of propagating aggregate link usage information. Furthermore, existing preemption schemes can be used with CAIP in order to decide the actual LSPs which need to be preempted.

Dynamic Resource Allocation for Multimedia Document Retrieval over High Speed LANs

The emergence of gigabit local area networks (G-LANs) has spurred a tremendous interest in supporting networked multimedia applications over a LAN. In this paper, we propose a mechanism for dynamically allocating network resources in asynchronous LANs. Presentation of multimedia objects with required play-out quality requires Quality of Service (QoS) guarantees by the underlying networking infrastructure. Existing asynchronous LANs, such as Ethernet, do not support the notion of QoS due to their asynchronous media access protocol. For such networks, we propose a dynamic bandwidth management scheme that uses the concept of Time Division Multiple Access (TDMA). Significant performance improvement is observed through experimental results. In particular, the transmission rates for multimedia hosts improve significantly with low jitter variations in media streams. We also propose a framework for graceful degradation of play-out quality of multimedia objects in case the LANs total capacity is not sufficient to meet the overall demand.

Transform domain inter-block interleaving schemes for robust image and video transmission in ATM networks

Abstract Data interleaving schemes have proven to be an important mechanism in reducing the impact of correlated network errors on image/video transmission. Current interleaving schemes fall into two main categories: (a) schemes that interleave pixel intensity values and (b) schemes that interleave JPEG/MPEG transform blocks. The schemes in the first category suffer in terms of lower compression ratio since highly correlated information in the spatial domain is de-correlated prior to compression. The schemes in the second category interleave DCT transformed blocks. In this case, in the absence of ARQ, if a packet is lost, an entire block may be lost thus yielding poor image quality and making the error concealment task difficult. Interleaving transform coefficients is tricky and error concealment in the presence of lost coefficients is challenging. In this paper, we develop three different interleaving schemes, namely Triangular, Quadrant, and Coefficient, that interleave frequency domain transform coefficients. The transform coefficients within each block are divided into small groups and groups are interleaved with the groups from other blocks in the image, hence they are referred to as inter-block interleaving schemes. The proposed schemes differ in terms of group size. In the Triangular interleaving scheme AC coefficients in each block are divided into two triangles and interleaving is performed among triangles from different blocks. In the Quadrant interleaving scheme, coefficients in each block are divided into four quadrants and quadrants are interleaved. In the Coefficient interleaving scheme, each coefficient in a block is a group and it is interleaved with the coefficients in other blocks. The compression ratio 3 of the proposed interleaving schemes is impressive ranging from 90 to 98% of the JPEG standard compression while providing much higher robustness in the presence of correlated losses. We also propose two new variable end-of-block (VEOB) techniques, one based on the number of AC coefficients per block (VAC-EOB) and the other based on the number of bits per block (VB–EOB). Our proposed interleaving techniques combined with VEOB schemes yield significantly better compression ratios compared to JPEG (2–11%) and MPEG-2 (3–6.7%) standards while at the same time improve the resilience of the coded data in the presence of transmission errors.

Error resilience of EZW coder for image transmission in lossy networks

We investigate the effect of network errors on Embedded Zerotree Wavelet (EZW) encoded images and propose modifications to the EZW coder to increase error resilience in bursty packet loss conditions. A hybrid-encoding scheme that uses data interleaving to spread correlated information into independently processed groups and layered encoding to protect significant information within each group is presented. Simulation results for various packet loss percentages show the improved error resiliency of our scheme in random and bursty packet loss environments.

A protocol architecture for guaranteed quality of service in collaborated multimedia applications

The role of multimedia applications in our day-to-day life has dramatically increased in the last few years. In this paper, we present an architectural framework for the distributed multimedia systems. The architecture consists of three layers: the application layer, the configuration and synchronization layer, and the network layer. The three layers are backed up by two backbone layers, namely, the database and the computational backbone. We present a precise description of each layer together with formal specifications using finite state automata.

Selective encryption based data security for Ogg streams

Existing solutions for securing multimedia streams such as RTP and Ogg, particularly those based on encrypting large portions of the data stream, are highly unscalable, and infringe on the Quality of Service (QoS) requirements as well. In this paper, we propose an efficient selective encryption technique for securing Ogg formatted VoIP/video streams. The proposed solution encrypts only 1.5% of the stream while guaranteeing security/privacy of the entire bit stream. Experimental results based on example hardware platforms while simulating different digital attacks are presented to verify the robustness of the proposed method.