An architecture of ATM‐based PCS network: Signaling traffic and capacity

In this paper, we propose an ATM‐based Personal Communication Service (PCS) network architecture with ring‐based access networks. We also propose a simple ring management scheme using ATM Add‐Drop‐Multiplexers (ADM). The ring has a Virtual Star topology, and we manage its bandwidth at two levels: Virtual Path (VP) level and Virtual Channel (VC) level. We consider four different types of configurations according to the locations of visitor location register (VLR) and mobile switching center (MSC) functions, and obtain signaling load and processing load. A 150 Mb/s‐dual ring can support about 5,500 homogeneous ON–OFF voice sources. This ring capacity corresponds to covering approximately 180 cells in the case of 30 connections per cell. Even though we are here concerned with evaluating the proposed network for voice traffic, we can extend this study to the analysis of the proposed ATM‐based PCS network accommodating various types of multimedia traffic as a further study. This revised version was published online in August 2006 with corrections to the Cover Date.     

A new approach to the design and analysis of peer‐to‐peer mobile networks

This paper introduces a new model and methodological approach for dealing with the probabilistic nature of mobile networks based on the theory of random graphs. Probabilistic dependence between the random links prevents the direct application of the theory of random graphs to communication networks. The new model, termed Random Network Model, generalizes conventional random graph models to allow for the inclusion of link dependencies in a mobile network. The new Random Network Model is obtained through the superposition of Kolmogorov complexity and random graph theory, making in this way random graph theory applicable to mobile networks. To the best of the authors' knowledge, it is the first application of random graphs to the field of mobile networks and a first general modeling framework for dealing with adhoc network mobility. The application of this methodology makes it possible to derive results with proven properties. The theory is demonstrated by addressing the issue of the establishment of a connected virtual backbone among mobile clusterheads in a peertopeer mobile wireless network. Using the Random Network Model, we show that it is possible to construct a randomized distributed algorithm which provides connectivity with high probability, requiring exponentially fewer connections (peertopeer logical links) per clusterhead than the number of connections needed for an algorithm with a worst case deterministic guarantee.     

Transient analysis of traffic generated by bursty sources,and its application to measurement‐based admission control

The first part of the paper is devoted to a transient analysis of traffic generated by bursty sources. These sources are governed by a modulating process, whose state determines the traffic rate at which the source transmits. The class of modulating processes contains, e.g., on/off traffic sources with general on and off times (but is considerably broader). We focus on the probability of extreme fluctuations of the resulting traffic rate, or more precisely, we determine the probability of the number of sources being in the on state reaching a certain threshold, given a measurement of the number of sources in the on state t units of time ago. In particular, we derive large deviations asymptotics of this probability when the number of sources is large. These asymptotics are numerically manageable, and it is empirically verified that they lead to an overestimation of the probability of our interest. The analysis is extended to alternative measurement procedures. These procedures allow to take into account, for instance, more historic measurements than just one, possibly combined with an exponential weighting of these measurements. In the second part of the paper, we apply the asymptotic calculation methods to gain insight into the feasibility of measurement‐based admission control (MBAC) algorithms for ATM or IP networks. These algorithms attempt to regulate the network's load (to provide the customers with a sufficient Quality of Service), and at the same time achieve an acceptable utilization of the resources. An MBAC algorithm may base acceptance or rejection of a new request on the measured momentary load imposed on the switch or router; if this load is below a given threshold, the source can be admitted. We investigate whether such a scheme is robust under the possible stochastic properties of the traffic offered. Both the burst level (i.e., the distribution of the on and off times of the sources) and the call level (particularly the distribution of the call duration) are taken into account. Special attention is paid to the influence of the bursts, silences, or call durations having a distribution with a “heavy tail”. This revised version was published online in June 2006 with corrections to the Cover Date.     

SPRD:fast application repackaging detection approach in Android based on application’s UI and program dependency graph

A two stage detection approach which combine application’s UI and program code based on the observation that repackaging applications merely modify the structure of their user interface was proposed.Firstly,a fast hash similarity detection technique based on an abstracted representation of UI to identify the potential visual-similar repackaging applications was designed.Secondly,program dependency graph is used to represent as the feature of app to achieve fine-grained and precise code clone detection.A prototype system,SPRD,was implemented based on the proposed approach.Experimental results show that the proposed approach achieves a good performance in both scalability and accuracy,and can be effectively applied in millions of applications and billions of code detection.     

An enhanced chaotic key‐based RC5 block cipher adapted to image encryption

RC5 is a block cipher that has several salient features such as adaptability to process different word lengths with a variable block size, a variable number of rounds and a variable‐length secret key. However, RC5 can be broken with various attacks such as correlation attack, timing attack, known plaintext correlation attack and differential attacks, revealing weak security. We aimed to enhance the RC5 block cipher to be more secure and efficient for real‐time applications while preserving its advantages. For this purpose, this article introduces a new approach based on strengthening both the confusion and diffusion operations by combining chaos and cryptographic primitive operations to produce round keys with better pseudo‐random sequences. Comparative security analysis and performance evaluation of the enhanced RC5 block cipher (ERC5) with RC5, RC6 and chaotic block cipher algorithm (CBCA) are addressed. Several test images are used for inspecting the validity of the encryption and decryption algorithms. The experimental results show the superiority of the suggested enhanced RC5 (ERC5) block cipher to image encryption algorithms such as RC5, RC6 and CBCA from the security analysis and performance evaluation points of view.     

An approach to linear and non-linear wave coupling using dispersion and energy relations †

By inclusion of an. external driving force, wave motion of any kind can be characterized by a dispersion function. This function is closely related to the energetic properties of wave motion, and then also to the averaged Lagrangian density. Linear and nonlinear wave interaction can be analysed by inclusion of internal driving forces. Normalization procedures for the amplitudes can be avoided and time and space perturbations studied simultaneously. This analysis is further connected to slowly varying amplitudes and quasi-monochromatic waves. This paper presents the above-mentioned method and applies it to linear two-wave coupling, and non-linear three-wave coupling between positive and negative energy waves, and finally to amplitude modulation. The general equations obtained by this procedure are useful for general discussions. The simplicity of the method may prove useful in different applications.     

Virtual tree‐based multicast routing with a distributed numbering algorithm for WM‐ATM handover

The flexibility offered by the ATM transport mechanism and its potential capabilities, together with its compatibility with the B‐ISDN, makes ATM the prime candidate for the support of multimedia services over the wireless medium. However, technical issues remain to be resolved in relation to the feasibility of ATM for the support of mobility over the radio interface. This paper examines network issues in supporting handover in a wireless ATM network. In particular, analysis has been performed for a virtual tree-based network architecture. Results have shown that by using multicast transmission and by using a distributed numbering algorithm, the potential problems of cell-loss and cell-duplication have been eliminated. This revised version was published online in June 2006 with corrections to the Cover Date.     

WaveVideo – An integrated approach to adaptive wireless video

The transmission of wireless video in acceptable quality is only possible by following an end-to-end approach. WaveVideo is an integrated, adaptive video coding architecture designed for heterogeneous wireless networks. It includes basic video compression algorithms based on wavelet transformations, an efficient channel coding, a filter architecture for receiver-based media scaling, and error-control methods to adapt video transmissions to the wireless environment. Using a joint source/channel coding approach, WaveVideo offers a high degree of error tolerance on noisy channels, still being competitive in terms of compression. Adaptation to channel conditions and user requirements is implemented on three levels. The coding itself features spatial and temporal measures to conceal transmission errors. Additionally, the amount of introduced error-control information is controlled by feedback. The video stream coding, applied to multicast capable networks, can serve different user's needs efficiently at the same time by scaling the video stream in the network according to receivers' quality requirements. The WaveVideo architecture is unique in terms of its capability to use QoS mapping and adaptation functions across all network nodes providing the same uniform interface.     

MA‐WATM: A new approach towards an adaptive wireless ATM network

In a cellular multimedia network like wireless ATM (WATM), self control seems primordial. Our new approach is based on the application of DAI (distributed artificial intelligence) techniques in order to build a selfadaptive network within random nonuniform traffic conditions. Attempting to achieve a high network capacity in terms of resource allocation and air interface BER (bit error rate), we propose to apply intelligent agent features to enhance the architecture of WATM systems. In fact, the intelligent platform MAWATM (multiagent wireless ATM) is used to provide a flexible integration of the multiagent technique in wireless entities, BSs (base stations), MSs (mobile stations) and MSCs (mobile switching centers). Two applications are investigated and explored by simulations in order to bear out the feasibility of the multiagent approach.     

An integrated GA–LP approach to communication network design

In this paper we demonstrate success with an implementation of a genetic algorithm, integrated with linear programming, for solving a minimum cost network synthesis problem. The problem is formulated to include a number of practical constraints and the technique applied to moderately large networks (50 nodes). The associated linear program may be large but successful methods have been developed with very small population sizes for the genetic algorithm. This revised version was published online in June 2006 with corrections to the Cover Date.     

Robustness Validation – A physics of failure based approach to qualification

Product reliability is crucial to the success of a company. Product qualification today is based on standards that follow a stress-test driven approach, meaning pre-defined stress tests with pre-defined stress conditions. However, reliability requirements have increased, while at the same time both designs of semiconductor components and usage of these components in the applications have increasingly been pushed to the limits. This development raises the question, how far the standard procedures are still suitable for reliability assessment. Robustness Validation is an approach to a failure-mechanism-driven qualification that was primarily initiated by the automotive industry but has a much wider range of applicability. The paper will give an introduction to the basic ideas of Robustness Validation. Some limitations including statistical aspects will also be discussed.     

Contactless vital signs monitoring based on few‐mode and multi‐core fibers

Few-mode and multi-core fibers are proposed and demonstrated for contactless vital signs monitoring in this paper.In-line optical fiber interferometers using few-mode and multi-core fibers are designed and offset splicing is utilized for mode excitation.Extinction ratio and insertion loss are analyzed experimentally under different offset distances.The fabricated in-line interferometers are packaged under the mattress to realize contactless vital signs signals collection.By using filtering techniques,both respiration and heartbeat signals can be recovered successfully,and respiration as well as heartbeat ratio are obtained.Mode excitation and interference are theoretically analyzed in few-mode fiber while curvature sensing experiments using multi-core fiber interferometer are performed to verify its excellent performance on vital signs monitoring.The successful demonstration on contactless vital signs monitoring makes few-mode and multi-core fibers promising candidates for healthcare applications.     

An optimized content delivery approach based on demand–supply theory in disruption-tolerant networks

Telecommunication Systems - Disruption-tolerance networks (DTNs) are suitable for applications that may lack continuous network connectivity. Examples of such applications include coupon...     

The interactive mobile social media advertising: An imminent approach to advertise tourism products and services?

Marketing tourism products traditionally were confined to conventional advertising tools. With the enhancement of mobile technologies and the emergence of social networking sites, a new platform of advertising has emerged. Mobile social media advertising refers to the use of social networking sites on mobile devices to advertise tourism products and services. However, many tourism organizations are skeptical, particularly if tourists are ready to accept this new form of advertising. Therefore, this study proposes an integrated framework that consists of Mobile Technology Acceptance Model, personal factors (i.e., mobile self-efficacy and technology self-efficacy), and Interactivity Theory to understand consumers’ intention to adopt mobile social media advertising in receiving tourism-related advertisements. 459 valid data were analyzed by the Partial Least Squares Structural Equation Modelling technique. Surprisingly, most structural paths are consistent with past literatures except for the relationship between personal factors and intention. This study has valuable contributions to academicians, practitioners, and society.     

A simplified approach to the performance evaluation of FDMA‐CDMA systems

This work shows it is possible to apply for the performance evaluation of FDMA‐CDMA cellular mobile systems a simple analytical approximated method, previously successfully proposed by two of the authors with reference to FDMA‐TDMA systems. The distinctive feature of the methodology we describe is that it allows for an immediate determination of both the indexes traditionally employed to define system performance, i.e., average bit error probability _e and outage probability P _out at a very low computational cost. The hypothesis required to apply the proposed approximation is that the examined spread spectrum system be characterized by a bandwidth occupancy lower than the coherence bandwidth of the transmission channel. This could be the case of a wireless DS‐CDMA system envisioned to provide voice service and exploiting a processing gain of the order of a hundred. We apply our methodology to determine the performance improvements in both _e and P _out introduced increasing the protection of the transmitted information through error correcting codes and interleaving, in different operating conditions as regards the functioning of the power control loops. A comparison is also satisfyingly carried out with some other approximated analytical methods found in literature. We strongly point out that the corresponding results are achieved at a much more modest computational cost than in traditional approaches. This revised version was published online in July 2006 with corrections to the Cover Date.     

Design and analysis of low‐power access protocols for wireless and mobile ATM networks

This paper describes the design and analysis of a low‐power medium access control (MAC) protocol for wireless/mobile ATM networks. The protocol – denoted EC‐MAC (energy conserving medium access control) – is designed to support different traffic types with quality‐of‐service (QoS) provisions. The network is based on the infrastructure model where a base station (BS) serves all the mobiles currently in its cell. A reservation‐based approach is proposed, with appropriate scheduling of the requests from the mobiles. This strategy is utilized to accomplish the dual goals of reduced energy consumption and quality of service provision over wireless links. A priority round robin with dynamic reservation update and error compensation scheduling algorithm is used to schedule the transmission requests of the mobiles. Discrete‐event simulation has been used to study the performance of the protocol. A comparison of energy consumption of the EC‐MAC to a number of other protocols is provided. This comparison indicates the EC‐MAC has, in general, better energy consumption characteristics. Performance analysis of the proposed protocol with respect to different quality‐of‐service parameters using video, audio and data traffic models is provided. This revised version was published online in August 2006 with corrections to the Cover Date.     

Novel optimal real‐time admission control and buffer management for the Video‐On‐Demand (VOD) service

In order to meet the Quality of Service (QoS) requirements of the VOD service, and, on the other hand, to maximize the system throughput (revenue), it is essential that the video call request admission control algorithm be carefully designed. In this paper, in addition to the Single Segment (SS) admission control first described in [7], we propose two new types of admission control schemes called Segmental Re‐tuned (SR) admission control and Multiple Segment (MS) admission control for variable‐bit‐rate video streams under various video server architectures. The basic approach to the algorithm development is first to formulate each problem as a mathematical problem and then to identify special structures and properties for such formulations so that optimal real‐time algorithms can be developed. In computational experiments, it is shown that the proposed algorithms for the considered video server architectures, compared with the traditional admission control scheme based upon the peak frame size, typically achieve over 175–200% improvement in the system throughput. In addition, the new proposed MS scheme performs 5–25% better than SS and SR schemes. This revised version was published online in June 2006 with corrections to the Cover Date.     

A new approach to long‐range dependence in variable bit rate video traffic

Recently it has been observed that variable bit rate (VBR) video traffic displays long‐range dependence, which suggests that traditional Markovian models may not be suitable for performance evaluation of telecommunications networks carrying this traffic. Inspection of the bit rate profile of VBR video traffic suggests that shifting level processes might be more appropriate for this task. In this paper we show that a particular class of these processes matches the autocorrelation and bit rate distribution of real VBR video traffic, including exhibiting long‐range dependent behaviour. This revised version was published online in June 2006 with corrections to the Cover Date.