Computer Science

Mobile applications stood top among usability and user convenience. Many applications are available in the market to manage personal and group expenses. Not many applications provides a comprehensive view of both use cases. In this project, we develop a mobile application that keeps track of user personal expenses, his/her personal contribution towards group expenses, maintain monthly incomes, recurring and adhoc payments. It provides information of "who owes who and by how much".

Multi-hop networks have gained a lot of interest in recent years. A lot of work was contributed in the field of protocol design and performance of multi-hop networks. It is generally accepted that mobility has a huge impact on the protocol performance; even more for multi-hop networks. Obtaining realistic measurements of mobility, however, is complex and expensive. Thus, we adopt virtual world scenarios to explore the mobility issue, by using the well-known multi-player game, Quake II. The advantage of the Quake II engine is that ...

Abstract—The Visualization Tool for Ad Hoc Networks—ViTAN is a tool for visualizing the connectivities and link qualities (capacities) between the terminals in wireless ad hoc networks. The ViTAN tool takes the location of the wireless terminals (specified by Cartesian coordinates) and the link qualities between the terminals as input. The tool produces a visualization of the graph of the terminals' connectivities in the fig format, which in turn can be converted to any common graphic format. ViTAN does not evaluate the connectivities ...

The wireless market is widely believed to be the most important future market for data services. Despite the efforts that were made to increase usability and abilities of all different wireless devices, the wireless protocol domain is still challenging. As new services and protocols emerge for wired networks, the need to incorporate those services and protocols in wireless communication systems arises. Existing wireless networks of the second generation (also known as 2G) are mostly circuit–switched and have been developed and ...

In this report we introduce the VideoMeter, a tool developed for the comparative evaluation of the quality of raw video data in the YUV format. The tool gives the differences in PSNR quality between two or three YUV video sequences and includes also a player for YUV video streams. In a typical application scenario, the tool is used for the quality assessment of videos that have been encoded with some lossy compression scheme and transported over a lossy network. The tool can be used to simultaneously play (i) the original YUV video ...

H. 26L is currently in the development status and is due to become standard according to the ITU–T and ISO/MPEG groups in late 2002. It will then become part of the H. 2xx, H. 3xx and MPEG standard families. H. 26L is expected to replace its predecessors H. 261 and H. 263, which were widely used in integrated circuits for telephone and video equipment for ISDN services over telephone networks. H. 26L has been designed with packet-switched networks in mind and has in its current implementation a complete network adaptation ...

Network security and authentication are very important for all kinds of communication networks to assure network stability and to avoid subscription fraud. In the last years–even for wireless local area networks–mechanisms have been found to support both in a cellular network. In multi–hop networks based on IEEE802. 11, security and authentication are still open issues. Mainly the low price of the network infrastructure makes this kind of networks vulnerable. Within the scope of this paper we describe the ...

Currently available video traces for scalable encoded video with more than one layer are a convenient representation of the encoded video for the evaluation of networking mechanisms. The video distortion (RMSE) or quality (PSNR) for individual video frames in these traces, however, only allow for the calculation of the video quality of correctly received video frames; for lossy network transport, only a rough approximation can be made. With the availability of scalable offset distortion traces, which we introduce and evaluate in this ...

In this paper we outline our future research activities in the area of wireless multi–hop communication systems. Our focus is on the link level design issues for IP based multi–hop communication systems using code division multiple access with pseudo–noise spreading sequences. We employ pseudo noise sequences to keep the signalling overhead low. In particular, we report on our initial design considerations and evaluations of a low complexity power control mechanism for multi–hop CDMA systems. Our Interference ...

ith the increasing popularity of networked multimedia applications, video data is expected to account for a large portion of the traffic in the Internet of the future and next-generation wireless systems. For transport over networks, video is typically encoded (i.e., compressed) to reduce the bandwidth requirements. Even compressed video, however, requires large bandwidths of the order of hundreds of kb/s or Mb/s, as will be shown later in this tutorial. In addition, compressed video streams typically exhibit highly variable bit rates (VBR) as well as long range dependence (LRD) properties, as will be demonstrated later in this tutorial. This, in conjunction with the stringent Quality of Service (QoS) requirements (loss and delay) of video traffic, makes the transport of video traffic over communication networks a challenging problem. As a consequence, in the last decade the networking research community has witnessed an explosion in research on all aspects of video transport. The characteristics of video traffic, video traffic modeling, as well as protocols and mechanisms for the efficient transport of video streams, have received a great deal of interest among networking researchers and network operators.

The performance evaluation of video transport mechanisms becomes increasingly important as encoded video accounts for growing portions of the network traffic. Compared to the widely studied MPEG-4 encoded video, the recently adopted H.264 video coding standards include novel mechanisms, such as hierarchical B frame prediction structures and highly efficient quality scalable coding, that have important implications for network transport. This tutorial introduces a trace-based evaluation methodology for the network transport of H.264 encoded video. We first give an overview of H.264 video coding, and then present the trace structures for capturing the characteristics of H.264 encoded video. We give an overview of the typical video traffic and quality characteristics of H.264 encoded video. Finally, we explain how to account for the H.264 specific coding mechanisms, such as hierarchical B frames, in networking studies.

We examine a recently proposed multichannel upgrade of optical single-channel ring networks where a subset of ring nodes is WDM upgraded and interconnected by a singlehop star WDM subnetwork in a pay-as-you-grow fashion. This evolutionary approach not only allows for fast and efficient multiple-failure recovery but also is well suited to efficiently sustain unpredictable changes and shifts in traffic loads. In this paper, we analytically investigate the maximum achievable capacity of the WDM star subnetwork upgrade of optical singlechannel networks under a variety of unicast and multicast traffic scenarios and compare it to that of conventional WDM ring networks. In our analysis, we take priority of ring in-transit traffic, destination stripping, and maximum spatial reuse into account. Our findings show that under multicast traffic the configuration of the star subnetwork plays an important role in order to achieve high multicast capacity. Furthermore, under multicast traffic WDM upgrading and interconnecting a subset of ring nodes might be sufficient to achieve a larger multicast capacity than in WDM rings.

Encoded video is expected to contribute a significant portion of the load on future communication systems and networks, which often employ statistical multiplexing. In such systems, the number of video streams that can be supported depends both on the mean bit rate as well as bit rate variability of the video streams. At the same time, the utility (revenue) earned from video streaming depends both on the number of supported video streams as well as their quality level. In this paper we examine the interplay between video quality, traffic variability, and utility for open-loop encoded video. We introduce the rate variability-distortion (VD) curve which relates the bit rate variability to the quality level of an encoded video. We find that the VD curve generally exhibits a characteristic "hump" behavior of first increasing, peaking, and subsequently decreasing variability for increasing quality. We examine the impact of video content characteristics, encoding parameters, and traffic smoothing on the VD behavior. We describe a methodology for assessing (i) the set of the video streams that can be supported with a statistical quality of service requirement, and (ii) the utility earned from video streaming over a link. This methodology is based on the rate-distortion and rate variability-distortion characteristics of the videos. We find that the statistical multiplexing gain and the utility as a function of the video quality level typically exhibit a "hump" similar to the VD curve.

Multimedia networking has been emerging in recent years as a strong driving force behind the expansion of the Internet. However, this topic is not commonly covered in the already content-intensive introductory networking courses. To facilitate student self-study of this novel topic the authors have developed a computer-based instructional module on the fundamentals of multimedia networking. In this paper, they describe the design and development of the module, which is aligned with Gagne's theory of instruction. They have developed two versions of the module-one with equation-based representation of the learning content and one with graph-based representation of the learning content. They have evaluated the two versions of the module with a total of 75 undergraduate, senior-level electrical engineering students, of which half were randomly assigned to the equational representation, and the other half to the graphical representation. They found that the graphical representation results in statistically significantly higher student performance on practice and post-test problems, shorter learning time, and more positive attitudes toward the computerbased instructional module.

Research has shown that providing instructional prompts in computer-based learning environments designed to support example-based learning fosters learning. In computerbased environments, where learners interact only with a computer and do not have access to direct support from a teacher, learners need to be provided with instructional prompts or just-in-time help intended to encourage more active example processing during learning. This study investigated whether it was more beneficial to provide the learners access to on-demand (self-regulated) help after they committed an error in problem solving or for the learning environment to regulate the presentation of instructional help externally. Furthermore, two different presentational formats-textual and pictorial-of instructional prompts were examined. This study was conducted with a computer-based learning environment that introduced high school students without any prior content-specific knowledge to the principles of parallel and series circuit analysis. Textual prompts facilitated practice problem solving notably better than pictorial prompts. Overall, textual-based prompts produced a large effect on near transfer. A significant format of prompts by academic ability interaction was discovered on near transfer. In particular, lower-ability learners scored significantly better when given textual prompts; whereas, their higher-ability counterparts performed equally well with both formats. Moreover, learners provided with externally regulated prompts reported significantly more positive attitudes toward the prompts in general compared to learners in the self-regulated conditions. Finally, continuous motivation was significantly stronger in learners who viewed textual prompts than in their counterparts in the pictorial prompt groups.

Packet-switched unidirectional and bidirectional ring wavelength division multiplexing (WDM) networks with destination stripping provide an increased capacity due to spatial wavelength reuse. Besides unicast traffic, future destination stripping ring WDM networks also need to support multicast traffic efficiently. This article examines the largest achievable transmitter throughput, receiver throughput, and multicast throughput of both unidirectional and bidirectional ring WDM networks with destination stripping. A probabilistic analysis evaluates both the nominal capacity, which is based on the mean hop distances travelled by the multicast packet copies, and the effective capacity, which is based on the ring segment with the highest utilization probability, for each of the three throughput metrics. The developed analytical methodology accommodates not only multicast traffic with arbitrary multicast fanout but also unicast and broadcast traffic. Numerical investigations compare the nominal transmission, receiver, and multicast capacities with the effective transmission, receiver, and multicast capacities and examine the impact of number of ring nodes and multicast fanout on the effective transmission, reception, and multicast capacity of both types of ring networks for different unicast, multicast, and broadcast traffic scenarios and different mixes of unicast and multicast traffic. The presented analytical methodology enables the evaluation and comparison of future multicast-capable medium access control (MAC) protocols for unidirectional and bidirectional ring WDM networks in terms of transmitter, receiver, and multicast throughput efficiency.

Fine granularity scalability (FGS), a new coding technique that has recently been added to the MPEG-4 video coding standard, allows for the flexible scaling of each individual video frame at very fine granularity. This flexibility makes FGS video very well suited for rate-distortion optimized streaming mechanisms, which minimize the distortion (i.e. maximize the quality) of the streamed video by transmitting the optimal number of bits for each individual frame. The per-frame optimization of the transmission schedule, however, puts a significant computational burden on video servers and intermediate streaming gateways. In this paper we investigate the rate-distortion optimized streaming at different video frame aggregation levels. We find that compared to the optimization for each individual video frame, optimization at the level of video scenes reduces the computational effort dramatically, while reducing the video quality only very slightly.