Teaching embedded software concepts using Android

Does smartphone application development provide an opportunity to explore various aspects of embedded software? This question is the primary motivator behind the ideas explored in this paper. We cannot deny the ubiquitous nature of smartphones. Leveraging on this already available "platform" to convey embedded software concepts to Computer Science (CS) students seems an exciting opportunity. Traditionally CS have often shied away from the field of embedded systems owing to their perception of this area as "hardware" oriented, not without reason. We explore the Android platform as a means of advancing embedded software concepts to CS students. Copyright 2010 ACM

Resource discovery and scheduling in unstructured peer-to-peer desktop grids

In this paper, we explore resource discovery and scheduling issues that arise in unstructured peer-to-peer (P2P) desktop grids. We examine the use of a super-peer based approach to address these issues. The super-peers form a resource information tracking and exchange overlay to enable users to rapidly locate resources for remote execution of jobs. Resource availability information is exchanged among the super-peers using a light-weight threshold-driven gossip protocol with the aim of minimizing the resource discovery overhead. We conduct detailed simulation experiments to illustrate the comparative results. Our results indicate that this approach offers a lightweight and scalable method for managing resources in a desktop grid. © 2010 IEEE

Applying adaptive virtual queue to improve the performance of the assured forwarding service

Recent research studies in the over-provisioned networks have shown that the Assured Forwarding (AF) service in the current Differentiated Services (Diffserv) architecture fails to provide bandwidth assurance in some situations. This paper focus on the situation where adaptive and non-adaptive traffic coexist in the same real queue at routers and the buffer management scheme treats the traffic of the same priority in the same AF class indiscriminately. An enhanced RIO is introduced, which can, without excessively penalizing non-adaptive flows, (1) significantly improve bandwidth assurance of adaptive AF flows; (2) alleviate the starvation imposed on adaptive best-effort flows. These goals are achieved by doing the folio wings when the failure of bandwidth assurance is detected, (1) mapping adaptive OUT traffic and non-adaptive OUT traffic to different virtual queues; (2) adapting the queue length thresholds according to whether the bandwidth assurance is achieved. We validate our design through simulations. © 2005 IEEE

Adaptive Marking Threshold for Improving Bandwidth Assurance in a Differentiated Services Network

Recent research studies have shown that Assured Forwarding (AF) service in the current Differentiated Services (Diffserv) framework does not provide bandwidth assurance in some circumstances. This paper proposes an adaptive marking threshold mechanism, called Adaptive CIR Threshold (ACT), which aims to improve bandwidth assurance for aggregate flows sharing the same AF class only based local knowledge. Extensive simulation results demonstrate significant improvement with ACT in bandwidth assurance under various conditions: different Round Trip Times (RTT), different numbers of micro-flows in an aggregate, different target rates, different packet sizes, and the presence of non-adaptive flows, compared with earlier mechanisms proposed in the literature

A robust PI controller for improving performance in the AF-based differentiated services network

The Assured Forwarding (AF) based service in a Differentiated Services (Diffserv) network fails to provide bandwidth assurance to aggregates in some circumstances. Several intelligent marking mechanisms have been proposed in the literature to improve bandwidth assurance for aggregates using the knowledge gathered at the ingress nodes. In this paper, we apply a control theoretic approach to this problem. We design a nonlinear Proportional-Integral (NPI) controller, called NPI-ACT, for adapting the CIR threshold. Performance results using extensive simulations demonstrate significant improvement using NPI-ACT in achieving bandwidth assurance over a wide range of network conditions compared to earlier mechanisms proposed in the literature

ReCap: A tool for automated capture and generation of synchronized audio, PowerPoint and digital ink presentation

In this paper we present ReCap, a tool for automated capture and creation of synchronized audio, Power Point and digital ink presentation in Real media format. Our tool creates the presentation based on the capture of a classroom lecture in real-time. Our tool is built using several technologies including .Net framework, Microsoft.Ink, Active X, SMIL and RealPix. While the tool can be used on any standard PC running Windows with .Net 1.1 framework, the use and capture of digital ink requires a Tablet PC. Recorded presentations are then made available through a podcast which students can subscribe using any podcast receiver. A slide level and pen stroke level indexed presentation is also supported on any browser supporting Active X, like Internet Explorer. By avoiding full-fledged video capture, file sizes are significantly reduced, typically requiring only about 10 Mb for a one-hour lecture. Another salient feature of our tool is that it requires no post-processing to create the synchronized media, thus saving significant postproduction effort. ReCap requires minimal hardware support: a windows-based PC with sound recording capability for capturing the lecture dynamics, and a web server with PHP support. The system has been extensively used by the authors in the classroom and has received positive feedback from the students

An integral sliding mode based AQM mechanism for stable queue length

Significant research effort has been devoted to designing robust Active Queue Management (AQM) mechanisms for the Internet, with mixed results. In this paper, we apply sliding mode control theory plus integral control to design a robust controller for AQM, which stabilizes the instantaneous queue length around the desired value with fast transient response over a wide range of network dynamics. We validate our design through extensive simulations and compare its performance with some AQM mechanisms published in the literature. © 2004 IEEE

Podcasting and its use in enhancing course content

Podcasting has recently seen rapid expansion as a means of delivering audio content to listeners. In this paper we report our experience with the use of podcasting as a means of delivering online recorded audio of classroom lectures to enhance the course materials. We achieved this with minimal institutional and infrastructure support in contrast to other such studies reported in the literature. We believe that podcasting will see rapid adoption in the higher education sector. Thus our experience sharing is intended to provide an example of how the new technology can be adopted in teaching and learning

Packet marking strategies for explicit congestion notification (ECN)

The Transmission Control Protocol (TCP) has congestion control mechanisms built into the protocol which reacts to congestion within the network by appropriately adjusting the sending rate of the TCP source. The congestion control mechanisms use packet drops as a means to detect congestion occurring in the network. Unnecessary packet drops lead to poor performance for low-bandwidth delay-sensitive applications like telnet. Explicit Congestion Notification (ECN) is a proposed mechanism that provide feedback to the sources about impending congestion in the routers without needing to drop packets at the congested routers. This requires support at the router to mark the ECN bit of the IP packet based on mechanisms to identify congestion, like Random Early Detection (RED). In this paper, we examine three different marking strategies, viz., mark-tail, mark-front and mark-random, to mark a packet in the presence of impending congestion. We examine the throughput performance of ECN flows and the unfairness among the ECN flows. We also show the throughput performance of new TCP flows with ECN. We also study the interaction between ECN and non-ECN flows

Sustaining TCP Throughput Using Assured Forwarding and ECN in a Differentiated Services Network

This paper examines the interaction among the congestion control mechanisms built into the Transmission Control Protocol (TCP), the Assured Forwarding (AF) PHB of Differentiated Services (Diffserv) mechanism, and Explicit Congestion Notification (ECN) mechanism. We show that ECN improves the fairness in sharing excess bandwidth among different AF flows. We then propose two mechanisms: (a) Out marking scheme, and (b) throughput sustaining scheme to foster cooperation between ECN and AF mechanism to further improve the throughput of TCP sources. Our results show that the new schemes achieve significant improvement in the TCP throughput performance