Igor Radovanovic

Ethernet-based passive optical local-area networks for fiber-to-the-desk application

We introduce optical local-area network (LAN) architectures based on multimode optical fiber and components, short wavelength lasers and detectors, and the widely used fast Ethernet protocol. These architectures are designed to lower the costs associated with passive optical LAN implementation. Further reduction in overall cost is achieved through decreased network downtime, lower maintenance cost, extended geometrical spans, and larger headroom for future capacity increase. These optically transparent networks represent a novel approach for implementing fiber-to-the-desk.

Enhancing End-to-End QoS for Multimedia Streaming in IMS-Based Networks

Convergence of the emerging IP Multimedia Subsystem(IMS) includes unlicensed, nondedicated and nondeterministic hence uncontrollable. computer access, networks for IP multimedia services. It enables provision of resource demanding real-time services and multimedia communication raising new end-to-end Quality-of-Service (QoS) challenges, for which quality adaptation using resource management is proposed as a solution in this paper. This is an integrated solution taking both IMS and computer access networks into account as well as the two end-devices and the application servers (AS) involved in communication. The best user experience is targeted under real-time variation of available network (e.g. bandwidth, buffer space) and end-device (e.g. battery, CPU, memory, storage) resources throughout a session. The multimedia content is dynamically adapted to fit the resource availability variations, achieving maximum system (i.e. network and end-devices) resource utilization and enhanced QoS. The resource availability update signalling is carried over Session Initiation Protocol (SIP) during the session. This is work in progress.

VICSDA: using virtual communities to secure service discovery and access

Service Oriented Architecture (SOA) is emerging as an enabling technology for sharing distributed heterogeneous resources on the network. Consequently, securing services is an increasing concern. Research issues include privacy protection for service providers, transparent access control for service consumers, secure service discovery and composition. In this paper, we present an access control approach which uses virtual communities to secure service discovery and access (VICSDA). Services grouped in virtual communities can only be discovered and accessed by authenticated community members. Meanwhile, services are autonomous to define their local access control policy. Moreover, behavior of these autonomous services is monitored in order to guarantee a better QoS provision. Using a virtual community overlay network on top of a SOA infrastructure, VICSDA can provide authentication, message confidentiality and integrity to secure service discovery and access. Better application performance can be achieved through VICSDA. We integrated VICSDA with a 3D video streaming application. This example provides us with some initial evidence that VICSDA is a viable solution to our target problems.

Allocation of in-home network resources to competing multimedia streams using EDCA

The wireless standard IEEE 802.11e provides Quality of Service (QoS) support allowing prioritized sharing of the channel bandwidth by a set of competing devices. This is particularly relevant for wireless in-home networks that are used by the Consumer Electronics (CE) devices that provide various quality levels of multimedia streaming services. The IEEE 802.11e standard supports a cooperative distributed control of the bandwidth sharing (EDCA) through a set of parameters that can be controlled by the communicating devices. This paper investigates the impact of these parameters on the bandwidth sharing through extensive simulations. We study several system setups of communicating pairs which can be regarded as generating competing multimedia traffic of different quality. Our simulation results show sensitivity of channel bandwidth allocation, and inherently sensitivity of QoS of multimedia streams, to the parameter change. The effect of individual parameter changes for various fixed values of other parameters is shown, based on which values of the individual parameters can be set to provide the required QoS. The presented results can provide the basis for embedding parameter settings into the system software of the CE devices.

Virtual community management for enabling P2P services in the IMS network

This paper addresses forming and management of a virtual community (VC) in the IP multimedia subsystem (IMS) network. A VC provides scope for mobile peer-to-peer (P2P) service sharing among end users and allows them control of sharing. The paper describes a number of services that enable forming and management of virtual communities and presents several service-oriented system architecture alternatives focusing on distribution of service access control and service discovery control between end users and operators as the owners of the IMS home-networks. Presented architecture alternatives are IMS compatible since they only introduce 5 additional services into the existing IMS architecture. A key service is an orchestrator that exposes new services composed of other services. A proof-of-concept realization of the IMS architecture in which control of mobile service sharing is distributed among end users and operators is shown.

Improving TCP performance over last-hop wireless networks for live video delivery

This paper discusses a link layer protocol that enhances performance of the Transmission Control Protocol (TCP) over a last-hop wireless network (LHWN) to make it more suitable for delivery of a live video with a short play out deadline. The presented protocol provides preference control of the transmission of video data within the network and it maximizes network goodput (the successfully transmitted amount of useful video data) by maximizing reliability of transmission for a given playout deadline and a varying digital bandwidth. The protocol makes use of the skip function in the TCP receiver to maximize end-to-end throughput of the connection at the expense of reducing full reliability. It can be implemented in a wireless access point to improve quality of the received live video over an Internet connection to an office or home. The main ideas of the protocol are: hide packet losses from the sender by performing local retransmissions based on the information from the video application and according to a certain scheduling policy, drop stale segments before they arrive at the receiver and prevent end-to-end retransmissions of segments received by the access point. The performance of the TCP Reno protocol in combination with both the presented protocol and the skip function in the receiver is compared against the performance of TCP Reno, the TCP-Real-Time Mode (RTM) protocol, TCP Reno in combination with the Snoop protocol and TCP-RTM in combination with Snoop. The results of simulations show improvement of network goodput across a wide range of packet-error rates.

Facilitating Mobile Service Provisioning in IP Multimedia Subsystem (IMS) Using Service Oriented Architecture

This paper presents an extension of the IMS software architecture using a service orientation, which provides flexibility of mobile service provisioning. The suggested extension facilitates composition of new mobile services in run-time based on the existing services and enables the end users to become mobile service providers. Moreover, it enables addition of new mobile services with plug-n-play similar to an addition of an end user device to the network. With this extension, the core system architecture of IMS is not affected. The extension is realized by introducing Web services in combination with the SIP protocol. Using SIP will enable operators to remain in control of mobile service provisioning as they are the owners of the IMS networks. This property of the extension may also facilitate its acceptance by the operators. A proof-of-concept prototype is discussed to demonstrate feasibility of the proposed extension.

Multimedia Adaptation with SIP Resource Availability Signalling in IMS Networks

Unlicensed, nondedicated and nondeterministic computer access networks are included in IP multimedia subsystem (IMS) in addition to the operator core network, which arises new end-to-end quality-of-service (QoS) issues for multimedia streaming. The resource availability of the network and the end-devices change drastically during a single multimedia session, which may cause a significant degradation in the overall user experience. In this paper, a multimedia content and quality adaptation framework depending on resource availability signalling over session initiation protocol (SIP) is proposed as a solution to this problem. Availability of network resources (e.g. bandwidth, buffer space) and end-device resources (e.g. battery, CPU, memory, storage) during a session is monitored and signalled over the network in real-time by the resource managers residing at both ends of the session. This framework is compliant with the IMS standard and is implemented as a plug-in.

Improving TCP/IP Performance over Last-hop Wireless Networks for Streaming Video Delivery

This paper discusses a protocol for delivery of streaming video with a short play-out deadline over a last-hop wireless network, which trades reliability for latency. This protocol could be implemented in the wireless access point to improve the quality of the received streaming video over an Internet connection to an office or home. The main ideas of the protocols are two-fold: 1) across the wireless link: perform local retransmissions and drop any stale packets; 2) across the entire source-destination path: hide duplicated acknowledgements from the sender to avoid retransmissions. In addition, the protocol takes advantage of application level framing and acknowledges missing transport layer segments with expired play-out deadlines. Although several existing protocols partially solve the problem of streaming video delivery in this particular context, either by improving the performance of the wireless link or by dropping the stale packets, to our best knowledge none of the protocols solves the complete problem. The performance of our protocol is compared against the performance of the snoop, TCP RTM, combined with snoop and TCP RTM protocols, as well as TCP Reno. The results of simulations show a manyfold improvement of the goodput across a wide range of packet-error rates.

Virtual community based secure service discovery and access for 3D video steaming applications

The Freeband I-Share project aims to define the mechanisms for trust, willingness, resource discovery and sharing mechanisms in virtual communities. To improve the secure and performance of a 3D video streaming application, which is a research vehicle of the I-Share project, we propose a virtual community based access control approach for secure service discovery and access (VICSDA) which groups services in virtual communities and only grants authenticated community members to discover and access these community services. There are two main contributions associated with this approach. First, different from most of the other access control approaches it adopts a dual access control mechanism which allows community services to define their local access control policy besides following the community membership policy. Second, behavior of these community services is monitored in order to guarantee a better QoS provision. Using this approach, the 3D video streaming application can be guaranteed with authentication and message confidentiality through the dual secure service discovery and access mechanism. Better application performance can also be achieved through the community member behavior audit.