Alexander A. Kist

Dynamic topologies for sustainable and energy efficient traffic routing

In light of the global focus on greenhouse gas emissions, energy consumption of communication networks has become an important research area. Networks are major energy consumers and are generally dimensioned for peak loads. For extended periods, resources consume power, but are lightly or unused. This research investigates the concept of dynamic topologies, i.e. networks that adapt their topology according to traffic volume. The key aim of this study is to investigate power reductions that can be achieved by dynamic topologies. It proposes a network transformation and introduces mathematical programming models that results in energy optimal topologies for given traffic loads. This paper focuses on the optimisation problems and investigates gains in static environments. Numerical results are presented for example networks using a large set of traffic matrices. For the test networks, dynamic topologies reduce the average network power consumption, depending on the network load, by approximately 12-52%.

SIP Signalling Delay in 3GPP

The Session Initiation Protocol (SIP) will be used as the signalling protocol in the IP Multimedia Subsystem (IMS) of 3rd Generation Partnership Project (3GPP) UMTS networks. This paper discusses the delay as a relevant signalling Quality of Service (QoS) parameter.

Real-Time Remote Access Laboratory With Distributed and Modular Design

Remote access laboratories (RALs) are online environments for operating instruments and collecting measurement data over the Internet. Such systems are often deployed by universities to support undergraduate students and generally follow the client-server paradigm. This paper discusses a RAL system that enables peer-to-peer (P2P) experimental design and sharing. For this, a modular design is required, which allows participating nodes to create rigs and host those individually at distributed locations. The proposed architecture is generic and can be used with any distributed P2P network control systems over the Internet. In this paper, a distributed remote control framework is presented with regard to a P2P RAL system. The experiments in the RAL require three subsystems handling the user interface, instruction interpretation, and instruction execution which can be organized and operated in different manners depending upon the experiment. The key component for creating and controlling experiments is the microcontrollers that can be easily obtained, configured, and set up for use over the Internet. The most popular microcontrollers are examined for suitability to the distributed control architecture. The basic layout of a message-based network protocol suitable for programming the devices and communication between peers for remote instrumentation and control is discussed, and queuing and flow control mechanisms are compared and tested for the proposed framework.

Instant Handoffs for Wireless Infrastructure Meshed Networks

Infrastructure meshed networks provide access to wireless clients that do not participate in traffic forwarding. This paper proposes minimalist instant handoff for wireless access networks (MIHAN), allowing for seamless movement of nodes in coverage areas, while maintaining connectivity. The approach of MIHAN is that all client frames, send in radio range of an access node, are received and forwarded to a central gateway. The node removes duplicate packets and tracks the network attachment of wireless clients. MIHAN relies on standard medium access control and a TCP/IP protocol stack. It is transparent to and does not require any special support, in the clients. Only limited configuration changes are necessary in the access nodes; all routing and tracking is handled by the gateway. Advantages include instant handoffs, no changes to access points and protocols and the simplicity of the solution. The paper introduces the scheme, provides details on various implementation options and gives simulation results that show the operation. Proof of concept implementation and some test results are presented.

Robot RAL-ly international - Promoting STEM in elementary school across international boundaries using remote access technology

Engaging school children early in STEM activities plays an important role in their choice to study engineering in later years. This paper describes a pilot project where Remote Access Laboratory technology at a university is employed in an inquiry-based learning activity with elementary school children in Japan and Australia. Investigation into how RAL technology facilitated collaborative learning in the K-12 demographic was then examined. Children in Japan designed a track that was constructed by their peers in Australia. The Japanese students then navigated the track in Australia with remotely controlled robots using the RAL system. A number of camera feeds allowed the students to observe the robots and the track. Both groups of students, as well as the participant researchers, took part in co-constructed focus group discussions after the event. A thematic analysis indicates that these activities provide students with opportunities for rich learning experiences in science, math and technology. Engaging young children in STEM activities provides a strong pathway to a better understanding of science concepts and ultimately a career in engineering.

An overview of system architectures for Remote Laboratories

Remote Access Laboratories have been successfully installed around the world enabling students to practice practical skills and develop their knowledge through experimentation. Remote laboratories have the advantage of being accessible from anywhere anytime allowing users more flexibility and mobility. Typically installations are designed to resolve issues of access or utilization. Clear pedagogical design is now seen as a critical development in the instigation of new experiments, and access systems. This paper examines existing system designs, using a Program Logic analysis to identify key inputs, outputs, and impacts for the creation of systems. It aims to identify commonalities, or differentiation with respect to the original goals. Through this analysis it was identified that many RAL systems implement direct mimic user interface design focusing on individual access to a kinesthetic learning experience. Learning design is also typically implemented by the system and experiment designers, potentially reducing the impact of the system or activity usability.

Using virtual SIP links to enable QoS for signalling

The session initiation protocol (SIP) was used on a large scale as a session signalling protocol to provide legacy as well as new services. The 3rd Generation Partnership Project (3GPP) has decided to use the SIP protocol in the IP multimedia subsystem of future Universal Mobile Telecommunications System (UMTS) networks. If the SIP protocol is used in carrier grade networks, quality of service (QoS) observations are necessary to ensure quality service provisioning. This, in particular, is important since signalling will use multiservice IP transport networks and share its resources with other services. This paper proposes the concept of virtual SIP links (VSLs) that connect two SIP nodes. VSLs can be used to enable QoS provisioning in SIP signalling overlay networks. Methodologies are introduced to specify, define and dimension these virtual connections. The VSL specification uses the well-known concept of leaky buckets. Simple methodologies are established that are based on known results, to calculate message loss probabilities (MLPs) in leaky buckets. A simple, but efficient, queueing scheme is introduced that reduces the required network resources. Simulation results are given to validate the used models and to underline performance advantages for connections that use VSLs.

A Novel Traffic Rate Measurement Algorithm for Quality of Experience-Aware Video Admission Control

With the inevitable dominance of video traffic on the Internet, providing perceptually good video quality is becoming a challenging task. This is partly due to the bursty nature of video traffic, changing network conditions, and limitations of network transport protocols. This growth of video traffic has made quality of experience (QoE) of the end user the focus of the research community. In contrast, Internet service providers are concerned about maximizing revenue by accepting as many sessions as possible, as long as customers remain satisfied. However, there is still no entirely satisfactory admission algorithm for flows with variable rate. The trade-off between the number of sessions and perceived QoE can be optimized by exploiting the bursty nature of video traffic. This paper proposes a novel algorithm to determine the upper limit of the aggregate video rate that can exceed the available bandwidth without degrading the QoE of accepted video sessions. A parameter β that defines the exceedable limit is defined . The proposed algorithm results in accepting more sessions without compromising the QoE of ongoing video sessions. Thus it contributes to the optimization of the QoE-Session trade-off in support of the expected growth of video traffic on the Internet.

Using network enabled microcontrollers in experiments for a distributed remote laboratory

Remote access laboratories are being used by universities to provide access to experiments through web based online environments. Usually, such experiments setups are an extension of the real hardware used in on-site laboratories. For a maker oriented RAL, users are encouraged to build their own experiment setups based on their understanding of the concepts and share them with their peers. Such a RAL system is targeted towards school level experiments. This poses a new problem of compiling equipment from an improvised set of tools, typically available at home or in schools. This is very different from the sophisticated laboratory equipment used in universities. In this paper, characteristics of such a RAL system are discussed and commercially available microcontroller boards to implement them are compared. Methods to operate these rigs based on a messaging protocol and an analysis of their performance in communicating with the network are presented.

Scheme for alternative packet overflow routing (SAPOR)

Shortest path routing schemes, like open shortest path first (OSPF), have shortcomings when networks are highly loaded. Traffic engineering of IP networks is required to avoid this problem. Current efforts suggest the optimisation of OSPF weights to balance the network load more evenly. Also, more advanced technologies, like multiprotocol label switching (MPLS), are proposed. One major problem of dynamic routing efforts that use OSPF is the fact that many traffic flows are influenced by single weight changes. We introduce SAPOR (scheme for alternative packet overflow routing), which realises a methodology that can remember the routing of packets for the duration of a micro flow. This allows the rerouting of overflow traffic. In this case, well known concepts and methodologies from conventional circuit switched teletraffic engineering can be adapted for IP networks.